ghopp
/
server_playground
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
Another abandoned server code base... this is kind of an ancestor of taskrambler.
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
129 Commits
1 Branch
0 Tags
51 MiB
 
 
 
 
 
 
Tree: 10f00ec3d3
Branches Tags
${ item.name }
Create tag ${ searchTerm }
Create branch ${ searchTerm }
from '10f00ec3d3'
${ noResults }
server_playground/doc/www.w3.org/TR/rdfa-core.1

4206 lines
314 KiB
Raw Blame History

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML+RDFa 1.0//EN' 'http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd'>
<html dir="ltr" about="" property="dcterms:language" content="en" xmlns="http://www.w3.org/1999/xhtml" xmlns:dcterms='http://purl.org/dc/terms/' xmlns:bibo='http://purl.org/ontology/bibo/' xmlns:foaf='http://xmlns.com/foaf/0.1/' xmlns:xsd='http://www.w3.org/2001/XMLSchema#'>
<head>
<title>RDFa Core 1.1</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<!--
=== NOTA BENE === For the three scripts below, if your spec resides on dev.w3 you can check them out in the same tree and use relative links so that they'll work offline, -->
<style type="text/css">
code { font-family: monospace; }
span.hilite { color: red; /* font-weight: bold */ }
li p { margin-top: 0.3em;
margin-bottom: 0.3em; }
div.explanation { background-color: #ADD8E6;
width: 80%;
margin: 12px; padding: 8px; }
div.explanation li { margin-top: 8px; }
div.explanation dd { margin: 4px; }
.adef {
font-family: monospace;
font-weight: bold;
color: #ff4500 !important;
}
.aref {
font-family: monospace;
font-weight: bold;
color: #ff4500 !important;
}
span.entity { color: red; }
span.element { color: green; }
</style>
<!-- <script src='/ReSpec.js/js/respec.js' class='remove'></script> -->
<style type="text/css">
/*****************************************************************
* ReSpec CSS
* Robin Berjon (robin at berjon dot com)
* v0.05 - 2009-07-31
*****************************************************************/
/* --- INLINES --- */
em.rfc2119 {
text-transform: lowercase;
font-variant: small-caps;
font-style: normal;
color: #900;
}
h1 acronym, h2 acronym, h3 acronym, h4 acronym, h5 acronym, h6 acronym, a acronym,
h1 abbr, h2 abbr, h3 abbr, h4 abbr, h5 abbr, h6 abbr, a abbr {
border: none;
}
dfn {
font-weight: bold;
}
a.internalDFN {
color: inherit;
border-bottom: medium solid #99c;
text-decoration: none;
}
a.externalDFN {
color: inherit;
border-bottom: medium dotted #ccc;
text-decoration: none;
}
a.bibref {
text-decoration: none;
}
code {
color: #ff4500;
}
/* --- WEB IDL --- */
pre.idl {
border-top: 1px solid #90b8de;
border-bottom: 1px solid #90b8de;
padding: 1em;
line-height: 120%;
}
pre.idl::before {
content: "WebIDL";
display: block;
width: 150px;
background: #90b8de;
color: #fff;
font-family: initial;
padding: 3px;
font-weight: bold;
margin: -1em 0 1em -1em;
}
.idlType {
color: #ff4500;
font-weight: bold;
text-decoration: none;
}
/*.idlModule*/
/*.idlModuleID*/
/*.idlInterface*/
.idlInterfaceID {
font-weight: bold;
color: #005a9c;
}
.idlSuperclass {
font-style: italic;
color: #005a9c;
}
/*.idlAttribute*/
.idlAttrType, .idlFieldType {
color: #005a9c;
}
.idlAttrName, .idlFieldName {
color: #ff4500;
}
.idlAttrName a, .idlFieldName a {
color: #ff4500;
border-bottom: 1px dotted #ff4500;
text-decoration: none;
}
/*.idlMethod*/
.idlMethType {
color: #005a9c;
}
.idlMethName {
color: #ff4500;
}
.idlMethName a {
color: #ff4500;
border-bottom: 1px dotted #ff4500;
text-decoration: none;
}
/*.idlParam*/
.idlParamType {
color: #005a9c;
}
.idlParamName {
font-style: italic;
}
.extAttr {
color: #666;
}
/*.idlConst*/
.idlConstType {
color: #005a9c;
}
.idlConstName {
color: #ff4500;
}
.idlConstName a {
color: #ff4500;
border-bottom: 1px dotted #ff4500;
text-decoration: none;
}
/*.idlException*/
.idlExceptionID {
font-weight: bold;
color: #c00;
}
.idlTypedefID, .idlTypedefType {
color: #005a9c;
}
.idlRaises, .idlRaises a.idlType, .idlRaises a.idlType code, .excName a, .excName a code {
color: #c00;
font-weight: normal;
}
.excName a {
font-family: monospace;
}
.idlRaises a.idlType, .excName a.idlType {
border-bottom: 1px dotted #c00;
}
.excGetSetTrue, .excGetSetFalse, .prmNullTrue, .prmNullFalse, .prmOptTrue, .prmOptFalse {
width: 45px;
text-align: center;
}
.excGetSetTrue, .prmNullTrue, .prmOptTrue { color: #0c0; }
.excGetSetFalse, .prmNullFalse, .prmOptFalse { color: #c00; }
.idlImplements a {
font-weight: bold;
}
dl.attributes, dl.methods, dl.constants, dl.fields {
margin-left: 2em;
}
.attributes dt, .methods dt, .constants dt, .fields dt {
font-weight: normal;
}
.attributes dt code, .methods dt code, .constants dt code, .fields dt code {
font-weight: bold;
color: #000;
font-family: monospace;
}
.attributes dt code, .fields dt code {
background: #ffffd2;
}
.attributes dt .idlAttrType code, .fields dt .idlFieldType code {
color: #005a9c;
background: transparent;
font-family: inherit;
font-weight: normal;
font-style: italic;
}
.methods dt code {
background: #d9e6f8;
}
.constants dt code {
background: #ddffd2;
}
.attributes dd, .methods dd, .constants dd, .fields dd {
margin-bottom: 1em;
}
table.parameters, table.exceptions {
border-spacing: 0;
border-collapse: collapse;
margin: 0.5em 0;
width: 100%;
}
table.parameters { border-bottom: 1px solid #90b8de; }
table.exceptions { border-bottom: 1px solid #deb890; }
.parameters th, .exceptions th {
color: #fff;
padding: 3px 5px;
text-align: left;
font-family: initial;
font-weight: normal;
text-shadow: #666 1px 1px 0;
}
.parameters th { background: #90b8de; }
.exceptions th { background: #deb890; }
.parameters td, .exceptions td {
padding: 3px 10px;
border-top: 1px solid #ddd;
vertical-align: top;
}
.parameters tr:first-child td, .exceptions tr:first-child td {
border-top: none;
}
.parameters td.prmName, .exceptions td.excName, .exceptions td.excCodeName {
width: 100px;
}
.parameters td.prmType {
width: 120px;
}
table.exceptions table {
border-spacing: 0;
border-collapse: collapse;
width: 100%;
}
/* --- TOC --- */
.toc a {
text-decoration: none;
}
a .secno {
color: #000;
}
/* --- TABLE --- */
table.simple {
border-spacing: 0;
border-collapse: collapse;
border-bottom: 3px solid #005a9c;
}
.simple th {
background: #005a9c;
color: #fff;
padding: 3px 5px;
text-align: left;
}
.simple th[scope="row"] {
background: inherit;
color: inherit;
border-top: 1px solid #ddd;
}
.simple td {
padding: 3px 10px;
border-top: 1px solid #ddd;
}
.simple tr:nth-child(even) {
background: #f0f6ff;
}
/* --- DL --- */
.section dd > p:first-child {
margin-top: 0;
}
.section dd > p:last-child {
margin-bottom: 0;
}
.section dd {
margin-bottom: 1em;
}
.section dl.attrs dd, .section dl.eldef dd {
margin-bottom: 0;
}
/* --- EXAMPLES --- */
pre.example {
border-top: 1px solid #ff4500;
border-bottom: 1px solid #ff4500;
padding: 1em;
margin-top: 1em;
}
pre.example::before {
content: "Example";
display: block;
width: 150px;
background: #ff4500;
color: #fff;
font-family: initial;
padding: 3px;
font-weight: bold;
margin: -1em 0 1em -1em;
}
/* --- EDITORIAL NOTES --- */
.issue {
padding: 1em;
border: 1px solid #f00;
background: #ffc;
}
.issue::before {
content: "Issue";
display: block;
width: 150px;
margin: -1.5em 0 0.5em 0;
font-weight: bold;
border: 1px solid #f00;
background: #fff;
padding: 3px 1em;
}
.note {
padding: 1em;
border: 2px solid #cff6d9;
background: #e2fff0;
}
.note::before {
content: "Note";
display: block;
width: 150px;
margin: -1.5em 0 0.5em 0;
font-weight: bold;
border: 1px solid #cff6d9;
background: #fff;
padding: 3px 1em;
}
/* --- SYNTAX HIGHLIGHTING --- */
pre.sh_sourceCode {
background-color: white;
color: black;
font-style: normal;
font-weight: normal;
}
pre.sh_sourceCode .sh_keyword { color: #005a9c; font-weight: bold; } /* language keywords */
pre.sh_sourceCode .sh_type { color: #666; } /* basic types */
pre.sh_sourceCode .sh_usertype { color: teal; } /* user defined types */
pre.sh_sourceCode .sh_string { color: red; font-family: monospace; } /* strings and chars */
pre.sh_sourceCode .sh_regexp { color: orange; font-family: monospace; } /* regular expressions */
pre.sh_sourceCode .sh_specialchar { color: #ffc0cb; font-family: monospace; } /* e.g., \n, \t, \\ */
pre.sh_sourceCode .sh_comment { color: #A52A2A; font-style: italic; } /* comments */
pre.sh_sourceCode .sh_number { color: purple; } /* literal numbers */
pre.sh_sourceCode .sh_preproc { color: #00008B; font-weight: bold; } /* e.g., #include, import */
pre.sh_sourceCode .sh_symbol { color: blue; } /* e.g.+ */
pre.sh_sourceCode .sh_function { color: black; font-weight: bold; } /* function calls and declarations */
pre.sh_sourceCode .sh_cbracket { color: red; } /* block brackets (e.g., {, }) */
pre.sh_sourceCode .sh_todo { font-weight: bold; background-color: #00FFFF; } /* TODO and FIXME */
/* Predefined variables and functions (for instance glsl) */
pre.sh_sourceCode .sh_predef_var { color: #00008B; }
pre.sh_sourceCode .sh_predef_func { color: #00008B; font-weight: bold; }
/* for OOP */
pre.sh_sourceCode .sh_classname { color: teal; }
/* line numbers (not yet implemented) */
pre.sh_sourceCode .sh_linenum { display: none; }
/* Internet related */
pre.sh_sourceCode .sh_url { color: blue; text-decoration: underline; font-family: monospace; }
/* for ChangeLog and Log files */
pre.sh_sourceCode .sh_date { color: blue; font-weight: bold; }
pre.sh_sourceCode .sh_time, pre.sh_sourceCode .sh_file { color: #00008B; font-weight: bold; }
pre.sh_sourceCode .sh_ip, pre.sh_sourceCode .sh_name { color: #006400; }
/* for Prolog, Perl... */
pre.sh_sourceCode .sh_variable { color: #006400; }
/* for LaTeX */
pre.sh_sourceCode .sh_italics { color: #006400; font-style: italic; }
pre.sh_sourceCode .sh_bold { color: #006400; font-weight: bold; }
pre.sh_sourceCode .sh_underline { color: #006400; text-decoration: underline; }
pre.sh_sourceCode .sh_fixed { color: green; font-family: monospace; }
pre.sh_sourceCode .sh_argument { color: #006400; }
pre.sh_sourceCode .sh_optionalargument { color: purple; }
pre.sh_sourceCode .sh_math { color: orange; }
pre.sh_sourceCode .sh_bibtex { color: blue; }
/* for diffs */
pre.sh_sourceCode .sh_oldfile { color: orange; }
pre.sh_sourceCode .sh_newfile { color: #006400; }
pre.sh_sourceCode .sh_difflines { color: blue; }
/* for css */
pre.sh_sourceCode .sh_selector { color: purple; }
pre.sh_sourceCode .sh_property { color: blue; }
pre.sh_sourceCode .sh_value { color: #006400; font-style: italic; }
/* other */
pre.sh_sourceCode .sh_section { color: black; font-weight: bold; }
pre.sh_sourceCode .sh_paren { color: red; }
pre.sh_sourceCode .sh_attribute { color: #006400; }
</style><link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css" charset="utf-8" /></head>
<body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C" /></a></p><h1 property="dcterms:title" class="title" id="title">RDFa Core 1.1</h1><h2 property="bibo:subtitle" id="subtitle">Syntax and processing rules for embedding RDF through attributes</h2><h2 property="dcterms:issued" datatype="xsd:dateTime" content="2011-12-15T06:00:00+0000" id="w3c-working-draft-15-december-2011"><acronym title="World Wide Web Consortium">W3C</acronym> Working Draft 15 December 2011</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2011/WD-rdfa-core-20111215/">http://www.w3.org/TR/2011/WD-rdfa-core-20111215/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/rdfa-core/">http://www.w3.org/TR/rdfa-core/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://www.w3.org/2010/02/rdfa/drafts#rdfa-core">http://www.w3.org/2010/02/rdfa/drafts#rdfa-core</a></dd><dt>Previous version:</dt><dd><a rel="dcterms:replaces" href="http://www.w3.org/TR/2011/WD-rdfa-core-20110331/">http://www.w3.org/TR/2011/WD-rdfa-core-20110331/</a></dd><dt>Latest recommendation:</dt><dd><a href="http://www.w3.org/TR/rdfa-syntax/">http://www.w3.org/TR/rdfa-syntax/</a></dd><dt>Editors:</dt><dd rel="bibo:editor"><span typeof="foaf:Person"><span property="foaf:name">Ben Adida</span>, Creative Commons <span class="ed_mailto"><a rel="foaf:mbox" href="mailto:ben@adida.net">ben@adida.net</a></span> </span>
</dd>
<dd rel="bibo:editor"><span typeof="foaf:Person"><span property="foaf:name">Mark Birbeck</span>, webBackplane <span class="ed_mailto"><a rel="foaf:mbox" href="mailto:mark.birbeck@webBackplane.com">mark.birbeck@webBackplane.com</a></span> </span>
</dd>
<dd rel="bibo:editor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Shane McCarron" href="http://blog.halindrome.com">Shane McCarron</a>, Applied Testing and Technology, Inc. <span class="ed_mailto"><a rel="foaf:mbox" href="mailto:shane@aptest.com">shane@aptest.com</a></span> </span>
</dd>
<dd rel="bibo:editor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Ivan Herman" href="http://www.w3.org/People/Ivan/">Ivan Herman</a>, <acronym title="World Wide Web Consortium">W3C</acronym> <span class="ed_mailto"><a rel="foaf:mbox" href="mailto:ivan@w3.org">ivan@w3.org</a></span> </span>
</dd>
</dl><p>This document is also available in these non-normative formats: <a href="rdfa-core-diff.html">Diff from previous Working Draft</a>, <a href="rdfa-core.ps">PostScript version</a>, and <a href="rdfa-core.pdf">PDF version</a>.</p><p class="copyright"><a rel="license" href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2007-2011 <span rel="dcterms:publisher"><span typeof="foaf:Organization"><a rel="foaf:homepage" property="foaf:name" content="World Wide Web Consotrium" href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup></span></span> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. <acronym title="World Wide Web Consortium">W3C</acronym> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p><hr /></div>
<div id="abstract" class="introductory section" property="dcterms:abstract" datatype="" typeof="bibo:Chapter" about="#abstract"><h2>Abstract</h2>
<p>The current Web is primarily made up of an enormous number of documents
that have been created using HTML. These documents contain significant
amounts of structured data, which is largely unavailable to tools and
applications. When publishers can express this data more completely, and
when tools can read it, a new world of user functionality becomes
available, letting users transfer structured data between applications
and web sites, and allowing browsing applications to improve the user
experience: an event on a web page can be directly imported into a
user's desktop calendar; a license on a document can be detected so that
users can be informed of their rights automatically; a photo's creator,
camera setting information, resolution, location and topic can be
published as easily as the original photo itself, enabling structured
search and sharing.</p>
<p>RDFa Core is a specification for attributes to express structured data
in any markup language. The embedded data already available in the
markup language (e.g., XHTML) can often be reused by the RDFa markup, so
that publishers don't need to repeat significant data in the document
content. The underlying abstract representation is RDF [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-PRIMER">RDF-PRIMER</a></cite>],
which lets publishers build their own vocabulary, extend others, and
evolve their vocabulary with maximal interoperability over time. The
expressed structure is closely tied to the data, so that rendered data
can be copied and pasted along with its relevant structure.</p>
<p>The rules for interpreting the data are generic, so that there is no
need for different rules for different formats; this allows authors and
publishers of data to define their own formats without having to update
software, register formats via a central authority, or worry that two
formats may interfere with each other.</p>
<p>RDFa shares some of the same goals with microformats [<cite><a class="bibref" rel="biblioentry" href="#bib-MICROFORMATS">MICROFORMATS</a></cite>].
Whereas microformats specify both a syntax for embedding structured data
into HTML documents and a vocabulary of specific terms for each
microformat, RDFa specifies only a syntax and relies on independent
specification of terms (often called vocabularies or taxonomies) by
others. RDFa allows terms from multiple independently-developed
vocabularies to be freely intermixed and is designed such that the
language can be parsed without knowledge of the specific vocabulary
being used. </p>
<p>This document is a detailed syntax specification for RDFa, aimed at:</p>
<ul>
<li>those looking to create an RDFa Processor, and who therefore need a
detailed description of the parsing rules;</li>
<li>those looking to integrate RDFa into a new markup language;</li>
<li>those looking to recommend the use of RDFa within their
organization, and who would like to create some guidelines for their
users;</li>
<li>anyone familiar with RDF, and who wants to understand more about
what is happening 'under the hood', when an RDFa Processor runs.</li>
</ul>
<p> For those looking for an introduction to the use of RDFa and some
real-world examples, please consult the <a href="http://www.w3.org/TR/xhtml-rdfa-primer/">RDFa
Primer</a>.</p>
<div typeof="bibo:Chapter" about="#how-to-read-this-document" class="section">
<h3 id="how-to-read-this-document">How to Read this Document</h3>
<p>First, if you are not familiar with either RDFa <em>or</em> RDF, and
simply want to add RDFa to your documents, then you may find the RDFa
Primer [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-PRIMER">RDFA-PRIMER</a></cite>] to be a better introduction.</p>
<p>If you are already familiar with RDFa, and you want to examine the
processing rules — perhaps to create an RDFa Processor — then you'll
find the <a href="#s_model">Processing Model</a> section of most
interest. It contains an overview of each of the processing steps,
followed by more detailed sections, one for each rule.</p>
<p>If you are not familiar with RDFa, but you <em>are</em> familiar
with RDF, then you might find reading the <a href="#s_Syntax_overview">Syntax
Overview</a> useful, before looking at the <a href="#s_model">Processing
Model</a> since it gives a range of examples of markup that use
RDFa. Seeing some examples first should make reading the processing
rules easier.</p>
<p>If you are not familiar with RDF, then you might want to take a look
at the section on <a href="#s_rdfterminology">RDF Terminology</a>
before trying to do too much with RDFa. Although RDFa is designed to
be easy to author — and authors don't need to understand RDF to use it
— anyone writing applications that <em>consume</em> RDFa will need to
understand RDF. There is a lot of material about RDF on the web, and a
growing range of tools that support RDFa, this document only contains
enough background on RDF to make the goals of RDFa more clear.</p>
<p class="note">RDFa is a way of expressing <em>RDF</em>-style
relationships using simple attributes in existing markup languages
such as HTML. RDF is fully internationalized, and permits the use of
Internationalized Resource Identifiers, or IRIs. You will see the term
'IRI' used throughout this specification. Even if you are not familiar
with the term IRI, you probably have seen the term 'URI' or 'URL'.
IRIs are an extension of URIs that permits the use of characters
outside those of plain ASCII. RDF allows the use of these characters,
and so does RDFa. This specification has been careful to use the
correct term, IRI, to make it clear that this is the case.</p>
</div>
</div><div id="sotd" class="introductory section" typeof="bibo:Chapter" about="#sotd"><h2>Status of This Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current <acronym title="World Wide Web Consortium">W3C</acronym> publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><acronym title="World Wide Web Consortium">W3C</acronym> technical reports index</a> at http://www.w3.org/TR/.</em></p>
<!-- <p>This document has been reviewed by W3C Members, by software
developers, and by other W3C groups and interested parties, and isendorsed by the Director as a W3C Recommendation. It is a stabledocument and may be used as reference material or cited from anotherdocument. W3C's role in making the Recommendation is to draw attention
to the specification and to promote its widespread deployment. Thisenhances the functionality and interoperability of the Web.</p> -->
<p>This version reflects changes made as a result of comments received
during a second Last Call period. That document was widely reviewed and
the Working Group has made significant improvements and clarifications
as a result. The Working Group believes that all comments received
during the last call have been addressed.</p>
<p>This is a revision of RDFa Syntax 1.0 [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-SYNTAX">RDFA-SYNTAX</a></cite>]. Once development
is complete, if accepted by the <acronym title="World Wide Web Consortium">W3C</acronym> membership, this document will
supersede the <a href="http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014">previous
Recommendation</a>. There are a number of substantive differences
between this version and its predecessor, including:</p>
<ol>
<li>The removal of the specific rules for XHTML - these are now defined
in XHTML+RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>]</li>
<li>An expansion of the datatypes of some RDFa attributes so that they
can contain Terms, CURIES, or Absolute IRIs.</li>
<li>Host languages are permitted to define collections of default terms,
default prefix mappings, and a default vocabulary.</li>
<li>The ability to define a default vocabulary to use for Terms that are
undefined.</li>
<li>Terms are required to be compared in a case-insensitive manner.</li>
<li>A richer behavior of the @property attribute, that can replace, in many cases the
@rel attribute.</li>
<li>A slightly different handling of @typeof, making it better adapted to practical usage.</li>
</ol>
<p>A <a href="http://rdfa.digitalbazaar.com/test-suite/">sample test
harness</a> is available. This set of tests is not intended to be
exhaustive. Users may find the tests to be useful examples of RDFa
usage.
<!--
An <a href="http://www.w3.org/2006/07/SWD/RDFa/implementation-report/">implementation report</a> lists several implementationsof this specification tested during the Candidate Recommendationperiod. A community-maintained <a href="http://rdfa.info/rdfa-implementations/">Wiki page</a> includes subsequent updates. -->
</p>
<p>This document was published by the <a href="http://www.w3.org/2010/02/rdfa">RDFa Working Group</a> as a Working Draft. This document is intended to become a <acronym title="World Wide Web Consortium">W3C</acronym> Recommendation. If you wish to make comments regarding this document, please send them to <a href="mailto:public-rdfa-wg@w3.org">public-rdfa-wg@w3.org</a> (<a href="mailto:public-rdfa-wg-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-rdfa-wg/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the <acronym title="World Wide Web Consortium">W3C</acronym> Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <acronym title="World Wide Web Consortium">W3C</acronym> Patent Policy</a>. <acronym title="World Wide Web Consortium">W3C</acronym> maintains a <a href="http://www.w3.org/2004/01/pp-impl/44350/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the <acronym title="World Wide Web Consortium">W3C</acronym> Patent Policy</a>.</p></div><div id="toc" typeof="bibo:Chapter" about="#toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#s_motivation" class="tocxref"><span class="secno">1. </span>Motivation</a></li><li class="tocline"><a href="#s_Syntax_overview" class="tocxref"><span class="secno">2. </span>Syntax Overview</a><ul class="toc"><li class="tocline"><a href="#rdfa-attributes" class="tocxref"><span class="secno">2.1 </span>The RDFa Attributes</a></li><li class="tocline"><a href="#examples" class="tocxref"><span class="secno">2.2 </span>Examples</a></li></ul></li><li class="tocline"><a href="#s_rdfterminology" class="tocxref"><span class="secno">3. </span>RDF Terminology</a><ul class="toc"><li class="tocline"><a href="#statements" class="tocxref"><span class="secno">3.1 </span>Statements</a></li><li class="tocline"><a href="#triples" class="tocxref"><span class="secno">3.2 </span>Triples</a></li><li class="tocline"><a href="#T-IRI-reference" class="tocxref"><span class="secno">3.3 </span>IRI references</a></li><li class="tocline"><a href="#plain-literals" class="tocxref"><span class="secno">3.4 </span>Plain literals</a></li><li class="tocline"><a href="#typed-literals" class="tocxref"><span class="secno">3.5 </span>Typed literals</a></li><li class="tocline"><a href="#turtle" class="tocxref"><span class="secno">3.6 </span>Turtle</a></li><li class="tocline"><a href="#graphs" class="tocxref"><span class="secno">3.7 </span>Graphs</a></li><li class="tocline"><a href="#compact-uri-expressions" class="tocxref"><span class="secno">3.8 </span>Compact URI Expressions</a></li><li class="tocline"><a href="#markup-fragments-and-rdfa" class="tocxref"><span class="secno">3.9 </span>Markup Fragments and RDFa</a></li><li class="tocline"><a href="#a-description-of-rdfa-in-rdf-terms" class="tocxref"><span class="secno">3.10 </span>A description of RDFa in RDF terms</a></li></ul></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">4. </span>Conformance</a><ul class="toc"><li class="tocline"><a href="#processorconf" class="tocxref"><span class="secno">4.1 </span>RDFa Processor Conformance</a></li><li class="tocline"><a href="#hostlangconf" class="tocxref"><span class="secno">4.2 </span>RDFa Host Language Conformance</a></li><li class="tocline"><a href="#xmlrdfaconformance" class="tocxref"><span class="secno">4.3 </span>XML+RDFa Document Conformance</a></li></ul></li><li class="tocline"><a href="#s_syntax" class="tocxref"><span class="secno">5. </span>Attributes and Syntax</a><ul class="toc"><li class="tocline"><a href="#white_space" class="tocxref"><span class="secno">5.1 </span>White space within attribute values</a></li></ul></li><li class="tocline"><a href="#s_curies" class="tocxref"><span class="secno">6. </span>CURIE Syntax Definition</a><ul class="toc"><li class="tocline"><a href="#why-curies-and-not-qnames" class="tocxref"><span class="secno">6.1 </span>Why CURIEs and not QNames?</a></li></ul></li><li class="tocline"><a href="#s_model" class="tocxref"><span class="secno">7. </span>Processing Model</a><ul class="toc"><li class="tocline"><a href="#overview" class="tocxref"><span class="secno">7.1 </span>Overview</a></li><li class="tocline"><a href="#evaluation-context" class="tocxref"><span class="secno">7.2 </span>Evaluation Context</a></li><li class="tocline"><a href="#s_chaining" class="tocxref"><span class="secno">7.3 </span>Chaining</a></li><li class="tocline"><a href="#s_curieprocessing" class="tocxref"><span class="secno">7.4 </span>CURIE and IRI Processing</a><ul class="toc"><li class="tocline"><a href="#scoping-of-prefix-mappings" class="tocxref"><span class="secno">7.4.1 </span>Scoping of Prefix Mappings</a></li><li class="tocline"><a href="#general-use-of-curies-in-attributes" class="tocxref"><span class="secno">7.4.2 </span>General Use of CURIEs in Attributes</a></li><li class="tocline"><a href="#s_terms" class="tocxref"><span class="secno">7.4.3 </span>General Use of Terms in Attributes</a></li><li class="tocline"><a href="#use-of-curies-in-specific-attributes" class="tocxref"><span class="secno">7.4.4 </span>Use of CURIEs in Specific Attributes</a></li><li class="tocline"><a href="#s_blankNodes" class="tocxref"><span class="secno">7.4.5 </span>Referencing Blank Nodes</a></li></ul></li><li class="tocline"><a href="#s_sequence" class="tocxref"><span class="secno">7.5 </span>Sequence</a></li><li class="tocline"><a href="#processor-status" class="tocxref"><span class="secno">7.6 </span>Processor Status</a><ul class="toc"><li class="tocline"><a href="#accessing-the-processor-graph" class="tocxref"><span class="secno">7.6.1 </span>Accessing the Processor Graph</a></li><li class="tocline"><a href="#processor-graph-terms" class="tocxref"><span class="secno">7.6.2 </span>Processor Graph Terms</a></li></ul></li><li class="tocline"><a href="#vocabulary-expansion" class="tocxref"><span class="secno">7.7 </span>Vocabulary Expansion</a></li></ul></li><li class="tocline"><a href="#s_rdfaindetail" class="tocxref"><span class="secno">8. </span>RDFa Processing in detail</a><ul class="toc"><li class="tocline"><a href="#changing-the-evaluation-context" class="tocxref"><span class="secno">8.1 </span>Changing the evaluation context</a><ul class="toc"><li class="tocline"><a href="#setting-the-current-subject" class="tocxref"><span class="secno">8.1.1 </span>Setting the current subject</a><ul class="toc"><li class="tocline"><a href="#the-current-document" class="tocxref"><span class="secno">8.1.1.1 </span>The current document</a></li><li class="tocline"><a href="#using--about" class="tocxref"><span class="secno">8.1.1.2 </span>Using <span class="aref formerLink aref" title="about">@about</span></a></li><li class="tocline"><a href="#typing-resources-with--typeof" class="tocxref"><span class="secno">8.1.1.3 </span>Typing resources with <span class="aref formerLink aref" title="typeof">@typeof</span></a><ul class="toc"><li class="tocline"><a href="#chaining-with--property-and--typeof" class="tocxref"><span class="secno">8.1.1.3.1 </span>Chaining with <span class="aref formerLink aref" title="property">@property</span> and <span class="aref formerLink aref" title="typeof">@typeof</span></a></li></ul></li><li class="tocline"><a href="#determining-the-subject-with-neither--about-nor--typeof" class="tocxref"><span class="secno">8.1.1.4 </span>Determining the subject with neither <span class="aref formerLink aref" title="about">@about</span> nor <span class="aref formerLink aref" title="typeof">@typeof</span></a><ul class="toc"><li class="tocline"><a href="#inheriting-subject-from--resource" class="tocxref"><span class="secno">8.1.1.4.1 </span>Inheriting subject from <span class="aref formerLink aref" title="resource">@resource</span></a></li><li class="tocline"><a href="#inheriting-an-anonymous-subject" class="tocxref"><span class="secno">8.1.1.4.2 </span>Inheriting an anonymous subject</a></li></ul></li></ul></li></ul></li><li class="tocline"><a href="#s_Completing_Incomplete_Triples" class="tocxref"><span class="secno">8.2 </span>Completing incomplete triples'</a></li><li class="tocline"><a href="#object-resolution" class="tocxref"><span class="secno">8.3 </span>Object resolution</a><ul class="toc"><li class="tocline"><a href="#object-resolution-for-the--property-attribute" class="tocxref"><span class="secno">8.3.1 </span>Object resolution for the <span class="aref formerLink aref" title="property">@property</span> attribute</a><ul class="toc"><li class="tocline"><a href="#plain-literals-1" class="tocxref"><span class="secno">8.3.1.1 </span>Plain Literals</a><ul class="toc"><li class="tocline"><a href="#language-tags" class="tocxref"><span class="secno">8.3.1.1.1 </span>Language Tags</a></li></ul></li><li class="tocline"><a href="#typed-literals-1" class="tocxref"><span class="secno">8.3.1.2 </span>Typed literals</a></li><li class="tocline"><a href="#s-xml-literals" class="tocxref"><span class="secno">8.3.1.3 </span><span title="xml-literals">XML Literals</span></a></li></ul></li><li class="tocline"><a href="#iri-object-resolution" class="tocxref"><span class="secno">8.3.2 </span>IRI object resolution</a><ul class="toc"><li class="tocline"><a href="#using--resource-to-set-the-object" class="tocxref"><span class="secno">8.3.2.1 </span>Using <span class="aref formerLink aref" title="resource">@resource</span> to set the object</a></li><li class="tocline"><a href="#using--href-or--src" class="tocxref"><span class="secno">8.3.2.2 </span>Using <span class="aref formerLink aref" title="href">@href</span> or <span class="aref formerLink aref" title="src">@src</span></a></li><li class="tocline"><a href="#incomplete-triples" class="tocxref"><span class="secno">8.3.2.3 </span>Incomplete triples</a></li></ul></li></ul></li><li class="tocline"><a href="#list-generation" class="tocxref"><span class="secno">8.4 </span>List generation</a></li></ul></li><li class="tocline"><a href="#s_initialcontexts" class="tocxref"><span class="secno">9. </span>RDFa Initial Contexts</a></li><li class="tocline"><a href="#s_vocab_expansion" class="tocxref"><span class="secno">10. </span><span>RDFa Vocabulary Expansion</span></a><ul class="toc"><li class="tocline"><a href="#s_vocab_expansion_details" class="tocxref"><span class="secno">10.1 </span><span>Details of the RDFa Vocabulary
Expansion</span></a><ul class="toc"><li class="tocline"><a href="#s_vocab_entailment" class="tocxref"><span class="secno">10.1.1 </span><span>RDFa Vocabulary Entailment</span></a></li></ul></li><li class="tocline"><a href="#s_expansion_control" class="tocxref"><span class="secno">10.2 </span>Vocabulary Expansion Control of RDFa Processors</a><ul class="toc"><li class="tocline"><a href="#s_vocab_guidelines" class="tocxref"><span class="secno">10.2.1 </span>Notes to RDFa Vocabulary Implementations and Publishing</a></li></ul></li></ul></li><li class="tocline"><a href="#s_datatypes" class="tocxref"><span class="secno">A. </span>CURIE Datatypes</a><ul class="toc"><li class="tocline"><a href="#xml-schema-definition" class="tocxref"><span class="secno">A.1 </span>XML Schema Definition</a></li><li class="tocline"><a href="#xml-dtd-definition" class="tocxref"><span class="secno">A.2 </span>XML DTD Definition</a></li></ul></li><li class="tocline"><a href="#vocabulary" class="tocxref"><span class="secno">B. </span>The RDFa Vocabulary</a><ul class="toc"><li class="tocline"><a href="#term-prefix-definitions-vocabulary" class="tocxref"><span class="secno">B.1 </span>Term and Prefix Assignments</a></li><li class="tocline"><a href="#processor-graph-reporting" class="tocxref"><span class="secno">B.2 </span>Processor Graph Reporting</a></li><li class="tocline"><a href="#vocabulary-relationship" class="tocxref"><span class="secno">B.3 </span>Term for vocabulary expansion</a></li><li class="tocline"><a href="#a_history" class="tocxref"><span class="secno">B.4 </span>Changes</a><ul class="toc"><li class="tocline"><a href="#major-differences-with-rdfa-syntax-1.0" class="tocxref"><span class="secno">B.4.1 </span>Major differences with RDFa Syntax 1.0</a></li></ul></li></ul></li><li class="tocline"><a href="#a_acks" class="tocxref"><span class="secno">C. </span>Acknowledgments</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">D. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">D.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">D.2 </span>Informative references</a></li></ul></li></ul></div>
<div class="informative section" id="s_motivation" typeof="bibo:Chapter" about="#s_motivation">
<!-- OddPage -->
<h2><span class="secno">1. </span>Motivation</h2><p><em>This section is non-normative.</em></p>
<p>RDF/XML [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX">RDF-SYNTAX</a></cite>] provides sufficient flexibility to represent all
of the abstract concepts in RDF [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]. However, it presents a
number of challenges; first it is difficult or impossible to validate
documents that contain RDF/XML using XML Schemas or DTDs, which
therefore makes it difficult to import RDF/XML into other markup
languages. Whilst newer schema languages such as RELAX NG
[<cite><a class="bibref" rel="biblioentry" href="#bib-RELAXNG-SCHEMA">RELAXNG-SCHEMA</a></cite>] do provide a way to validate documents that contain
arbitrary RDF/XML, it will be a while before they gain wide support.</p>
<p>Second, even if one could add RDF/XML directly into an XML dialect like
XHTML, there would be significant data duplication between the rendered
data and the RDF/XML structured data. It would be far better to add RDF
to a document without repeating the document's existing data. For
example, an XHTML document that explicitly renders its author's name in
the text—perhaps as a byline on a news site—should not need to repeat
this name for the RDF expression of the same concept: it should be
possible to supplement the existing markup in such a way that it can
also be interpreted as RDF.</p>
<p>Another reason for aligning the rendered data with the structured data
is that it is highly beneficial to express the web data's structure 'in
context'; as users often want to transfer structured data from one
application to another, sometimes to or from a non-web-based
application, the user experience can be enhanced. For example,
information about specific rendered data could be presented to the user
via 'right-clicks' on an item of interest.</p>
<p>In the past, many attributes were 'hard-wired' directly into the markup
language to represent specific concepts. For example, in XHTML 1.1
[<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML11">XHTML11</a></cite>] and HTML [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML401">HTML401</a></cite>] there is <span class="aref">@cite</span>;
the attribute allows an author to add information to a document which is
used to indicate the origin of a quote.</p>
<p>However, these 'hard-wired' attributes make it difficult to define a
generic process for extracting metadata from any document since an RDFa
Processor would need to know about each of the special attributes. One
motivation for RDFa has been to devise a means by which documents can be
augmented with metadata in a general, rather than hard-wired, manner.
This has been achieved by creating a fixed set of attributes and parsing
rules, but allowing those attributes to contain properties from any of a
number of the growing range of available RDF vocabularies. In most cases
the <em>values</em> of those properties are the information that is
already in an author's document.</p>
<p>RDFa alleviates the pressure on markup language designers to anticipate
all the structural requirements users of their language might have, by
outlining a new syntax for RDF that relies only on attributes. By
adhering to the concepts and rules in this specification, language
designers can import RDFa into their environment with a minimum of
hassle and be confident that semantic data will be extractable from
their documents by conforming processors. </p>
</div>
<div class="informative section" id="s_Syntax_overview" typeof="bibo:Chapter" about="#s_Syntax_overview">
<!-- OddPage -->
<h2><span class="secno">2. </span>Syntax Overview</h2><p><em>This section is non-normative.</em></p>
<p>The following examples are intended to help readers who are not
familiar with RDFa to quickly get a sense of how it works. For a more
thorough introduction, please read the RDFa Primer [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-PRIMER">RDFA-PRIMER</a></cite>].</p>
<p>In RDF, it is common for people to shorten vocabulary terms via
abbreviated IRIs that use a 'prefix' and a 'reference'. This mechanism
is explained in detail in the section titled <a>Compact URI Expressions</a>.
The examples throughout this document assume that the following
vocabulary <a class="tref" title="prefix" href="#T-prefix">prefixes</a> have been defined:</p>
<table>
<tbody>
<tr>
<td rowspan="1" colspan="1">bibo:</td>
<td rowspan="1" colspan="1">http://purl.org/ontology/bibo/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">cc:</td>
<td rowspan="1" colspan="1">http://creativecommons.org/ns#</td>
</tr>
<tr>
<td rowspan="1" colspan="1">dbp:</td>
<td rowspan="1" colspan="1">http://dbpedia.org/property/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">dbp-owl:</td>
<td rowspan="1" colspan="1">http://dbpedia.org/ontology/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">dbr:</td>
<td rowspan="1" colspan="1">http://dbpedia.org/resource/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">dc:</td>
<td rowspan="1" colspan="1">http://purl.org/dc/terms/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">ex:</td>
<td rowspan="1" colspan="1">http://example.org/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">foaf:</td>
<td rowspan="1" colspan="1">http://xmlns.com/foaf/0.1/</td>
</tr>
<tr>
<td rowspan="1" colspan="1">rdf:</td>
<td rowspan="1" colspan="1">
http://www.w3.org/1999/02/22-rdf-syntax-ns#</td>
</tr>
<tr>
<td rowspan="1" colspan="1">rdfa:</td>
<td rowspan="1" colspan="1"> http://www.w3.org/ns/rdfa#</td>
</tr>
<tr>
<td rowspan="1" colspan="1">rdfs:</td>
<td rowspan="1" colspan="1"> http://www.w3.org/2000/01/rdf-schema#</td>
</tr>
<!--
<tr> <td rowspan="1" colspan="1">taxo:</td> <td rowspan="1" colspan="1">http://purl.org/rss/1.0/modules/taxonomy/</td> </tr> -->
<tr>
<td rowspan="1" colspan="1">xhv:</td>
<td rowspan="1" colspan="1">http://www.w3.org/1999/xhtml/vocab#</td>
</tr>
<tr>
<td rowspan="1" colspan="1">xsd:</td>
<td rowspan="1" colspan="1">http://www.w3.org/2001/XMLSchema#</td>
</tr>
</tbody>
</table>
<p class="note">In some of the examples below we have used IRIs with
fragment identifiers that are local to the document containing the RDFa
fragment identifiers shown (e.g., '<code>about=&quot;#me&quot;</code>'). This
idiom, which is also used in RDF/XML [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>] and other
RDF serializations, gives a simple way to 'mint' new IRIs for entities
described by RDFa and therefore contributes considerably to the
expressive power of RDFa. Unfortunately, this practice is not at present
covered by the media type registrations that govern the meaning of
fragment identifiers (see section 3.5 of the URI specification
[<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3986">RFC3986</a></cite>], [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3023">RFC3023</a></cite>], and [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC2854">RFC2854</a></cite>]). For more information about
fragment identifier semantics, see [<cite><a class="bibref" rel="biblioentry" href="#bib-WEBARCH">WEBARCH</a></cite>] section 3.2.1.</p>
<div id="rdfa-attributes" typeof="bibo:Chapter" about="#rdfa-attributes" class="section">
<h3><span class="secno">2.1 </span>The RDFa Attributes</h3>
<p>RDFa makes use of a number of commonly found attributes, as well as
providing a few new ones. Attributes that already exist in widely
deployed languages (e.g., HTML) have the same meaning they always did,
although their syntax has been slightly modified in some cases. For
example, in (X)HTML there is no clear way to add new <a class="aref" href="#A-rel" title="rel">@rel</a>
values; RDFa sets out to explicitly solve this problem, and does so by
allowing IRIs as values. It also introduces the concepts of <a class="tref" title="term" href="#T-term">terms</a>
and '<a class="tref" title="curie" href="#T-curie">compact URI expressions</a>' — referred to
as CURIEs in this document — which allow a full IRI value to be
expressed succinctly. For a complete list of RDFa attribute names and
syntax, see <a href="#s_syntax">Attributes and Syntax</a>.</p>
</div>
<div id="examples" typeof="bibo:Chapter" about="#examples" class="section">
<h3><span class="secno">2.2 </span>Examples</h3>
<p>In HTML, authors can include metadata and relationships concerning
the current document by using the <code>meta</code> and <code>link</code>
elements. For example, the author of the page along with the pages
preceding and following the current page can be expressed using the
link and meta elements:</p>
<pre class="example">&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot;&gt;
&lt;head&gt;
&lt;title&gt;Page 7&lt;/title&gt;
<span class="hilite">&lt;meta name=&quot;author&quot; content=&quot;Mark Birbeck&quot; /&gt;</span>
<span class="hilite">&lt;link rel=&quot;prev&quot; href=&quot;page6.html&quot; /&gt;</span>
<span class="hilite">&lt;link rel=&quot;next&quot; href=&quot;page8.html&quot; /&gt;</span>
&lt;/head&gt;
&lt;body&gt;...&lt;/body&gt;
&lt;/html&gt;</pre>
<p>RDFa makes use of this concept, enhancing it with the ability to make
use of other vocabularies by using full IRIs:</p>
<pre class="example">&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot;&gt;
&lt;head&gt;
&lt;title&gt;My home-page&lt;/title&gt;
&lt;meta property=&quot;<span class="hilite">http://purl.org/dc/terms/creator</span>&quot; content=&quot;Mark Birbeck&quot; /&gt;
&lt;link rel=&quot;<span class="hilite">http://xmlns.com/foaf/0.1/topic</span>&quot; href=&quot;http://www.example.com/#us&quot; /&gt;
&lt;/head&gt;
&lt;body&gt;...&lt;/body&gt;
&lt;/html&gt;</pre>
<p>Because using full IRIs like those above can be cumbersome, RDFa also
permits the use of <a class="datatype internalDFN" title="CURIE" href="#dfn-curie">compact URI expressions</a>
so an author can use a shorthand to reference terms in multiple
vocabularies:</p>
<pre class="example">&lt;html
xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
<span class="hilite">prefix=&quot;foaf: http://xmlns.com/foaf/0.1/</span>
<span class="hilite">dc: http://purl.org/dc/terms/&quot;</span>
&gt;
&lt;head&gt;
&lt;title&gt;My home-page&lt;/title&gt;
&lt;meta property=&quot;<span class="hilite">dc:creator</span>&quot; content=&quot;Mark Birbeck&quot; /&gt;
&lt;link rel=&quot;<span class="hilite">foaf:topic</span>&quot; href=&quot;http://www.example.com/#us&quot; /&gt;
&lt;/head&gt;
&lt;body&gt;...&lt;/body&gt;
&lt;/html&gt;</pre>
<p>RDFa supports the use of <a class="aref" href="#A-rel" title="rel">@rel</a> and <a class="aref" href="#A-rev" title="rev">@rev</a> on
any element. This is even more useful with the addition of support for
different vocabularies:</p>
<pre id="ccLicense" class="example">This document is licensed under the
&lt;a <span class="hilite">prefix=&quot;cc: http://creativecommons.org/ns#&quot;</span>
<span class="hilite">rel=&quot;cc:license&quot;</span>
href=&quot;http://creativecommons.org/licenses/by-nc-nd/3.0/&quot;&gt;
Creative Commons By-NC-ND License
&lt;/a&gt;.</pre>
<p>Not only can IRIs in the document be re-used to provide metadata, but
so can inline text when used with <a class="aref" href="#A-property" title="property">@property</a>:</p>
<pre class="example">&lt;html
xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
<span class="hilite">prefix=&quot;cal: http://www.w3.org/2002/12/cal/ical#&quot;</span>
&gt;
&lt;head&gt;&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;&lt;/head&gt;
&lt;body&gt;
&lt;p&gt;
I'm holding
&lt;span <span class="hilite">property=&quot;cal:summary&quot;</span>&gt;
<span class="hilite">one last summer Barbecue</span>
&lt;/span&gt;,
on September 16th at 4pm.
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>If some displayed text is different to the actual 'value' it
represents, a more precise value can be added, which can optionally
include <a class="aref" href="#A-datatype" title="datatype">@datatype</a>:</p>
<pre class="example">&lt;html
xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
prefix=&quot;cal: http://www.w3.org/2002/12/cal/ical#
<span class="hilite">xsd: http://www.w3.org/2001/XMLSchema&quot;</span>
&gt;
&lt;head&gt;&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;&lt;/head&gt;
&lt;body&gt;
&lt;p&gt;
I'm holding
&lt;span property=&quot;cal:summary&quot;&gt;
one last summer Barbecue
&lt;/span&gt;,
on
&lt;span <span class="hilite">property=&quot;cal:dtstart&quot;</span> <span class="hilite">content=&quot;2015-09-16T16:00:00-05:00&quot;</span>
<span class="hilite">datatype=&quot;xsd:dateTime&quot;</span>&gt;
September 16th at 4pm
&lt;/span&gt;.
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>In many cases a block of markup will contain a number of properties
that relate to the same item; it's possible with RDFa to indicate the
type of that item using <a class="aref" href="#A-typeof" title="typeof">@typeof</a>:</p>
<pre class="example">&lt;html
xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
prefix=&quot;cal: http://www.w3.org/2002/12/cal/ical#
xsd: http://www.w3.org/2001/XMLSchema&quot;
&gt;
&lt;head&gt;&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;&lt;/head&gt;
&lt;body&gt;
&lt;p <span class="hilite">typeof=&quot;cal:Vevent&quot;</span>&gt;
I'm holding
&lt;span property=&quot;cal:summary&quot;&gt;
one last summer Barbecue
&lt;/span&gt;,
on
&lt;span property=&quot;cal:dtstart&quot; content=&quot;2015-09-16T16:00:00-05:00&quot;
datatype=&quot;xsd:dateTime&quot;&gt;
September 16th at 4pm
&lt;/span&gt;.
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>RDFa allows the document to contain metadata information about other
documents and resources:</p>
<pre class="example">&lt;html
xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
prefix=&quot;bibo: http://purl.org/ontology/bibo/
dc: http://purl.org/dc/terms/&quot;
&gt;
&lt;head&gt;
&lt;title&gt;Books by Marco Pierre White&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
I think White's book
'&lt;span <span class="hilite">about=&quot;urn:ISBN:0091808189&quot;</span> <span class="hilite">typeof=&quot;bibo:Book&quot;</span>
<span class="hilite">property=&quot;dc:title&quot;</span>&gt;
Canteen Cuisine
&lt;/span&gt;'
is well worth getting since although it's quite advanced stuff, he
makes it pretty easy to follow. You might also like
&lt;span <span class="hilite">about=&quot;urn:ISBN:1596913614&quot;</span> <span class="hilite">typeof=&quot;bibo:Book&quot;</span>
<span class="hilite">property=&quot;dc:description&quot;</span>&gt;
White's autobiography
&lt;/span&gt;.
&lt;/body&gt;
&lt;/html&gt;</pre>
<p> When dealing with small amounts of markup, it is sometimes easier to
use full IRIs, rather than CURIEs. The previous example can also be
written as follows:</p>
<pre class="example">&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot;&gt;
&lt;head&gt;
&lt;title&gt;Books by Marco Pierre White&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
I think White's book
'&lt;span
<span class="hilite">about=&quot;urn:ISBN:0091808189&quot;</span>
<span class="hilite">typeof=&quot;http://purl.org/ontology/bibo/Book&quot;</span>
<span class="hilite">property=&quot;http://purl.org/dc/terms/title&quot;</span>
&gt;Canteen Cuisine&lt;/span&gt;'
is well worth getting since although it's quite advanced stuff, he
makes it pretty easy to follow. You might also like
&lt;span
<span class="hilite">about=&quot;urn:ISBN:1596913614&quot;</span>
<span class="hilite">typeof=&quot;http://purl.org/ontology/bibo/Book&quot;</span>
<span class="hilite">property=&quot;http://purl.org/dc/terms/description&quot;</span>
&gt;White's autobiography&lt;/span&gt;.
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>A simple way of defining a portion of a document using terms from a
specific vocabulary is to use <a class="aref" href="#A-vocab" title="vocab">@vocab</a> to define a default
vocabulary IRI. For example, to use FOAF terms:</p>
<pre class="example">&lt;div <span class="hilite">vocab=&quot;http://xmlns.com/foaf/0.1/&quot;</span> about=&quot;#me&quot;&gt;
My name is &lt;span <span class="hilite">property=&quot;name&quot;</span>&gt;John Doe&lt;/span&gt; and my blog is called
&lt;a <span class="hilite">rel=&quot;homepage&quot;</span> href=&quot;http://example.org/blog/&quot;&gt;Understanding Semantics&lt;/a&gt;.
&lt;/div&gt;</pre>
<p>The example above will produce the following triples, expressed here
in <a href="#turtle">Turtle</a> syntax:</p>
<pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .
&lt;#me&gt; <span class="hilite">foaf:name</span> &quot;John Doe&quot; ;
<span class="hilite">foaf:homepage</span> &lt;http://example.org/blog/&gt; .</pre>
<p>In simple cases the <a class="aref" href="#A-property" title="property">@property</a> property can also be used
in place of <a class="aref" href="#A-rel" title="rel">@rel</a>. Indeed, in case when the element does
not contain <a class="aref" href="#A-rel" title="rel">@rel</a>, <a class="aref" href="#A-datatype" title="datatype">@datatype</a>, of <a class="aref" href="#A-content" title="content">@content</a>,
but there is, for example, a <a class="aref" href="#A-href" title="href">@href</a>, the effect of <a class="aref" href="#A-property" title="property">@property</a>
is analogous to the role of <a class="aref" href="#A-rel" title="rel">@rel</a>. For example, the
previous example could have been written:</p>
<pre class="example">&lt;div <span class="hilite">vocab=&quot;http://xmlns.com/foaf/0.1/&quot;</span> about=&quot;#me&quot;&gt;
My name is &lt;span <span class="hilite">property=&quot;name&quot;</span>&gt;John Doe&lt;/span&gt; and my blog is called
&lt;a <span class="hilite">property=&quot;homepage&quot;</span> href=&quot;http://example.org/blog/&quot;&gt;Understanding Semantics&lt;/a&gt;.
&lt;/div&gt;</pre> </div>
</div>
<div class="informative section" id="s_rdfterminology" typeof="bibo:Chapter" about="#s_rdfterminology">
<!-- OddPage -->
<h2><span class="secno">3. </span>RDF Terminology</h2><p><em>This section is non-normative.</em></p>
<p> The previous section gave examples of typical markup in order to
illustrate the structure of RDFa markup. RDFa is short for &quot;RDF in
Attributes&quot;. In order to author RDFa you do not need to understand RDF,
although it would certainly help. However, if you are building a system
that consumes the RDF output of a language that supports RDFa you will
almost certainly need to understand RDF. This section introduces the
basic concepts and terminology of RDF. For a more thorough explanation
of RDF, please refer to the RDF Concepts document [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>] and
the RDF Syntax Document [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX">RDF-SYNTAX</a></cite>]. </p>
<div id="statements" typeof="bibo:Chapter" about="#statements" class="section">
<h3><span class="secno">3.1 </span>Statements</h3>
<p> The structured data that RDFa provides access to is a collection of
<em>statements</em>. A statement is a basic unit of information that
has been constructed in a specific format to make it easier to
process. In turn, by breaking large sets of information down into a
collection of statements, even very complex metadata can be processed
using simple rules. </p>
<p> To illustrate, suppose we have the following set of facts:</p>
<pre class="example">Albert was born on March 14, 1879, in the German Empire. There is a picture of him at
the web address, http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.</pre>
<p>This would be quite difficult for a machine to interpret, and it is
certainly not in a format that could be passed from one data
application to another. However, if we convert the information to a
set of statements it begins to be more manageable. The same
information could therefore be represented by the following shorter
'statements':</p>
<pre class="example">Albert was born on March 14, 1879.
Albert was born in the German Empire.
Albert has a picture at
http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.</pre> </div>
<div id="triples" typeof="bibo:Chapter" about="#triples" class="section">
<h3><span class="secno">3.2 </span>Triples</h3>
<p> To make this information machine-processable, RDF defines a
structure for these statements. A statement is formally called a <dfn title="triple" id="T-triple"><em>triple</em></dfn>,
meaning that it is made up of three components. The first is the <em>subject</em>
of the triple, and is what we are making our statements <em>about</em>.
In all of these examples the subject is 'Albert'. </p>
<p> The second part of a triple is the property of the subject that we
want to define. In the examples here, the properties would be 'was
born on', 'was born in', and 'has a picture at'. These are more
usually called <em>predicates</em> in RDF. </p>
<p> The final part of a triple is called the <em>object</em>. In the
examples here the three objects have the values 'March 14, 1879', 'the
German Empire', and
'http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg'. </p>
<p class="note">RDFa has complete support for internationalized
characters. This includes internationalized characters in the subject,
property and object location.</p>
</div>
<div id="T-IRI-reference" typeof="bibo:Chapter" about="#T-IRI-reference" class="section">
<h3><span class="secno">3.3 </span>IRI references</h3>
<p> Breaking complex information into manageable units helps us be
specific about our data, but there is still some ambiguity. For
example, which 'Albert' are we talking about? If another system has
more facts about 'Albert', how could we know whether they are about
the same person, and so add them to the list of things we know about
that person? If we wanted to find people born in the German Empire,
how could we know that the predicate 'was born in' has the same
purpose as the predicate 'birthplace' that might exist in some other
system? RDF solves this problem by replacing our vague terms with <dfn title="iri-reference" id="T-iri-reference">IRI
references. </dfn></p>
<p> IRIs are most commonly used to identify web pages, but RDF makes use
of them as a way to provide unique identifiers for concepts. For
example, we could identify the subject of all of our statements (the
first part of each triple) by using the DBPedia [<a href="http://dbpedia.org">http://dbpedia.org</a>]
IRI for Albert Einstein, instead of the ambiguous string 'Albert':</p>
<pre class="example"><span class="hilite">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;</span>
has the name
Albert Einstein.
<span class="hilite">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;</span>
was born on
March 14, 1879.
<span class="hilite">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;</span>
was born in
the German Empire.
<span class="hilite">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;</span>
has a picture at
http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.</pre>
<p> IRI references are also used to uniquely identify the objects in
metadata statements (the third part of each triple). The picture of
Einstein is already an IRI, but we could also use an IRI to uniquely
identify the country 'German Empire'. At the same time we'll indicate
that the name and date of birth really are literals (and not IRIs), by
putting quotes around them:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
has the name
<span class="hilite">&quot;</span>Albert Einstein<span class="hilite">&quot;</span>.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
was born on
<span class="hilite">&quot;</span>March 14, 1879<span class="hilite">&quot;</span>.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
was born in
<span class="hilite">&lt;http://dbpedia.org/resource/German_Empire&gt;</span>.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
has a picture at
<span class="hilite">&lt;</span>http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg<span class="hilite">&gt;</span>.</pre>
<p> IRI references are also used to ensure that predicates are
unambiguous; now we can be sure that 'birthplace', 'place of birth',
'Lieu de naissance' and so on, all mean the same thing:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">&lt;http://xmlns.com/foaf/0.1/name&gt;</span>
&quot;Albert Einstein&quot;.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">&lt;http://dbpedia.org/property/dateOfBirth&gt;</span>
&quot;March 14, 1879&quot;.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">&lt;http://dbpedia.org/property/birthPlace&gt;</span>
&lt;http://dbpedia.org/resource/German_Empire&gt;.
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">&lt;http://xmlns.com/foaf/0.1/depiction&gt;</span>
&lt;http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg&gt;.</pre> </div>
<div id="plain-literals" typeof="bibo:Chapter" about="#plain-literals" class="section">
<h3><span class="secno">3.4 </span>Plain literals</h3>
<p> Although IRI resources are always used for subjects and predicates,
the object part of a triple can be either an IRI or a <dfn title="literal" id="T-literal"><em>literal</em></dfn>.
In the example triples, Einstein's name is represented by a <dfn title="plain-literal" id="T-plain-literal"><em>plain
literal</em></dfn>, which means that it is a basic string with no
type or language information:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
&lt;http://xmlns.com/foaf/0.1/name&gt; <span class="hilite">&quot;Albert Einstein&quot;</span>.</pre> </div>
<div id="typed-literals" typeof="bibo:Chapter" about="#typed-literals" class="section">
<h3><span class="secno">3.5 </span>Typed literals</h3>
<p> Some literals, such as dates and numbers, have very specific
meanings, so RDF provides a mechanism for indicating the type of a
literal. A <dfn title="typed-literal" id="T-typed-literal"><em>typed literal</em></dfn>
is indicated by attaching an IRI to the end of a <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a>,
and this IRI indicates the literal's datatype. This IRI is usually
based on datatypes defined in the XML Schema Datatypes specification
[<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>]. The following syntax would be used to unambiguously
express Einstein's date of birth as a literal of type <code>http://www.w3.org/2001/XMLSchema#date</code>:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
&lt;http://dbpedia.org/property/dateOfBirth&gt;
&quot;1879-03-14&quot;<span class="hilite">^^&lt;http://www.w3.org/2001/XMLSchema#date&gt;</span>.</pre> </div>
<div id="turtle" typeof="bibo:Chapter" about="#turtle" class="section">
<h3><span class="secno">3.6 </span>Turtle</h3>
<p> RDF itself does not have one set way to express triples, since the
key ideas of RDF are the triple and the use of IRIs, and <em>not</em>
any particular syntax. However, there are a number of mechanisms for
expressing triples, such as RDF/XML [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>], Turtle
[<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>], and of course RDFa. Many discussions of RDF make use of
the <em>Turtle</em> syntax to explain their ideas, since it is quite
compact. The examples we have just seen are already using this syntax,
and we'll continue to use it throughout this document when we need to
talk about the RDF that could be generated from some RDFa. Turtle
allows long IRIs to be abbreviated by using an IRI mapping, which can
be used to express a compact IRI expression as follows:</p>
<pre class="example"><span class="hilite">@prefix dbp: &lt;http://dbpedia.org/property/&gt; .</span>
<span class="hilite">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .</span>
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">foaf:name</span> &quot;Albert Einstein&quot; .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
<span class="hilite">dbp:birthPlace</span> &lt;http://dbpedia.org/resource/German_Empire&gt; .</pre>
<p>Here 'dbp:' has been mapped to the IRI for DBPedia and 'foaf:' has
been mapped to the IRI for the 'Friend of a Friend' taxonomy.</p>
<p>Any IRI in Turtle could be abbreviated in this way. This means that
we could also have used the same technique to abbreviate the
identifier for Einstein, as well as the datatype indicator:</p>
<pre class="example">@prefix dbp: &lt;http://dbpedia.org/property/&gt; .
<span class="hilite">@prefix dbr: &lt;http://dbpedia.org/resource/&gt; .</span>
@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .
<span class="hilite">@prefix xsd: &lt;http://www.w3.org/2001/XMLSchema#&gt; .</span>
<span class="hilite">dbr:Albert_Einstein</span> dbp:dateOfBirth &quot;1879-03-14&quot;^^<span class="hilite">xsd:date</span> .
<span class="hilite">dbr:Albert_Einstein</span>
foaf:depiction &lt;http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg&gt; .</pre>
<p> When writing examples, you will often see the following IRI in the
Turtle representation:</p>
<pre class="example">&lt;&gt;</pre>
<p> This indicates the 'current document', i.e., the document being
processed. In reality there would always be a full IRI based on the
document's location, but this abbreviation serves to make examples
more compact. Note in particular that the whole technique of
abbreviation is merely a way to make examples more compact, and the
actual triples generated would always use the full IRIs.</p>
</div>
<div id="graphs" typeof="bibo:Chapter" about="#graphs" class="section">
<h3><span class="secno">3.7 </span>Graphs</h3>
<p> A collection of triples is called a <em>graph</em>. All of the
triples that are defined by this specification are contained in the <a class="tref" title="output-graph" href="#T-output-graph">output
graph</a> by an RDFa Processor. For more information on graphs
and other RDF concepts, see [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]. </p>
</div>
<div id="compact-uri-expressions" typeof="bibo:Chapter" about="#compact-uri-expressions" class="section">
<h3><span class="secno">3.8 </span>Compact URI Expressions</h3>
<p>In order to allow for the compact expression of RDF statements, RDFa
allows the contraction of most <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>s into a
form called a 'compact URI expression', or <a class="datatype internalDFN" title="CURIE" href="#dfn-curie">CURIE</a>. A
detailed discussion of this mechanism is in the section <a href="#s_curieprocessing">CURIE
and IRI Processing</a>.</p>
<p>Note that CURIEs are only used in the markup and Turtle examples, and
will never appear in the generated <a class="tref" title="triple" href="#T-triple">triple</a>s, which are
defined by RDF to use <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>s.</p>
<p>Full details on how CURIEs are processed are in the section titled <a href="#s_curieprocessing">CURIE
Processing</a>.</p>
</div>
<div id="markup-fragments-and-rdfa" typeof="bibo:Chapter" about="#markup-fragments-and-rdfa" class="section">
<h3><span class="secno">3.9 </span>Markup Fragments and RDFa</h3>
<p>A growing use of embedded metadata is to take fragments of markup and
move them from one document to another. This may happen through the
use of tools, such as drag-and-drop in a browser, or through snippets
of code provided to authors for inclusion in their documents. (A good
example of the latter is the <a href="#ccLicense">licensing fragment
provided by Creative Commons</a>.)</p>
<p>However, those involved in creating fragments (either by building
tools, or authoring snippets), should be aware that this specification
does not say how fragments are processed. Specifically, the processing
of a fragment 'outside' of a complete document is undefined because
RDFa processing is largely about context. Future versions of this or
related specifications may do more to define this behavior.</p>
<p>Developers of tools that process fragments, or authors of fragments
for manual inclusion, should also bear in mind what will happen to
their fragment once it is included in a complete document. They should
carefully consider the amount of 'context' information that will be
needed in order to ensure a correct interpretation of their fragment.</p>
</div>
<div id="a-description-of-rdfa-in-rdf-terms" typeof="bibo:Chapter" about="#a-description-of-rdfa-in-rdf-terms" class="section">
<h3><span class="secno">3.10 </span>A description of RDFa in RDF terms</h3>
<p> The following is a brief description of RDFa in terms of the RDF
terminology introduced here. It may be useful to readers with an RDF
background: </p>
<p>The aim of RDFa is to allow a single <a class="tref" title="rdf-graph" href="#T-rdf-graph">RDF graph</a> to be
carried in various types of document markup. An <dfn title="rdf-graph" id="T-rdf-graph">RDF graph</dfn>
comprises <dfn title="node" id="T-node">node</dfn>s linked by relationships. The basic unit
of an <a class="tref" title="rdf-graph" href="#T-rdf-graph">RDF graph</a> is a <a class="tref" title="triple" href="#T-triple">triple</a>, in which a
subject <a class="tref" title="node" href="#T-node">node</a> is linked to an object <a class="tref" title="node" href="#T-node">node</a>
via a <a class="tref" title="predicate" href="#T-predicate">predicate</a>. The <dfn title="subject" id="T-subject">subject</dfn> <a class="tref" title="node" href="#T-node">node</a>
is always either a <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a> or a <dfn title="bnode" id="T-bnode">blank
node (or bnode)</dfn>, the <dfn title="predicate" id="T-predicate">predicate</dfn> is <em>always</em>
a <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>, and the object of a statement can be a
<a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>, a <a class="tref" title="literal" href="#T-literal">literal</a>, or a <a class="tref" title="bnode" href="#T-bnode">bnode</a>.</p>
<p>In RDFa, a subject <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a> is generally indicated
using <a class="aref" href="#A-about" title="about">@about</a> and predicates are represented using one of
<a class="aref" href="#A-property" title="property">@property</a>, <a class="aref" href="#A-rel" title="rel">@rel</a>, or <a class="aref" href="#A-rev" title="rev">@rev</a>.
Objects which are <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>s are represented using <a class="aref" href="#A-resource" title="resource">@resource</a>,
<a class="aref" href="#A-src" title="src">@src</a>, or <a class="aref" href="#A-href" title="href">@href</a>, whilst objects that are <a class="tref" title="literal" href="#T-literal">literal</a>s
are represented either with <a class="aref" href="#A-content" title="content">@content</a> or the content of
the element in question (with an optional datatype expressed using <a class="aref" href="#A-datatype" title="datatype">@datatype</a>,
and an optional language expressed using a Host Language-defined
mechanism such as <span class="aref">xml:lang</span>).</p>
</div>
</div>
<div id="conformance" class="normative section" typeof="bibo:Chapter" about="#conformance">
<!-- OddPage -->
<h2><span class="secno">4. </span>Conformance</h2><p>As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.</p>
<p>The key words <em class="rfc2119" title="must">must</em>, <em class="rfc2119" title="must not">must not</em>, <em class="rfc2119" title="required">required</em>, <em class="rfc2119" title="should">should</em>, <em class="rfc2119" title="should not">should not</em>, <em class="rfc2119" title="recommended">recommended</em>, <em class="rfc2119" title="may">may</em>, and <em class="rfc2119" title="optional">optional</em> in this specification are to be interpreted as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC2119">RFC2119</a></cite>].</p>
<div id="processorconf" typeof="bibo:Chapter" about="#processorconf" class="section">
<h3><span class="secno">4.1 </span>RDFa Processor Conformance</h3>
<p>A conforming RDFa Processor <em class="rfc2119" title="must">must</em> make available to a consuming
application a single <a class="tref" title="rdf-graph" href="#T-rdf-graph">RDF graph</a> containing all possible
triples generated by using the rules in the <a href="#s_model">Processing
Model</a> section. This specification uses the term <dfn title="output-graph" id="T-output-graph">output
graph</dfn> to mean all of the triples asserted by a document
according to the <a href="#s_model">Processing Model</a> section. The
term <dfn title="processor-graph" id="T-processor-graph">processor graph</dfn> is used to denote the collection of
all informational, warning, and error triples that may be generated by
the RDFa Processor to <a href="#processor-status">report its status</a>.
The <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> and the <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a>
are separate graphs and <em class="rfc2119" title="must not">must not</em> be stored in the same graph by the
RDFa Processor. </p>
<p>A conforming RDFa Processor <em class="rfc2119" title="may">may</em> make available additional triples
that have been generated using rules not described here, but these
triples <em class="rfc2119" title="must not">must not</em> be made available in the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>.
(Whether these additional triples are made available in one or more
additional <a class="tref" title="rdf-graph" href="#T-rdf-graph">RDF graph</a>s is implementation-specific, and
therefore not defined here.)</p>
<p>A conforming RDFa Processor <em class="rfc2119" title="must">must</em> preserve white space in both <a class="tref" title="plain-literal" href="#T-plain-literal">plain
literal</a>s and <a class="tref" title="xml-literals" href="#T-xml-literals">XML literals</a>.
However, it may be the case that the architecture in which a processor
operates has made changes to the white space in a document before that
document ever reaches the RDFa Processor (e.g., [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-1">XMLSCHEMA-1</a></cite>]
processors are permitted to 'normalize' white space in attribute
values - see section 3.1.4). To ensure maximum consistency between
processing environments, authors <em class="rfc2119" title="should">should</em> remove any unnecessary white
space in their plain and XML Literal content.</p>
<p>A conforming RDFa Processor <em class="rfc2119" title="must">must</em> examine the media type of a document
it is processing to determine the document's Host Language. If the
RDFa Processor is unable to determine the media type, or does not
support the media type, the RDFa Processor <em class="rfc2119" title="must">must</em> process the document
as if it were media type <code>application/xml</code>. See <a href="#xmlrdfaconformance">XML+RDFa
Document Conformance</a>. A Host Language <em class="rfc2119" title="may">may</em> specify additional
announcement mechanisms.</p>
<p class="note">A conforming RDFa Processor <em class="rfc2119" title="may">may</em> use additional
mechanisms (e.g., the DOCTYPE, a file extension, the root element) to
attempt to determine the Host Language if the media type is
unavailable. These mechanisms are unspecified.</p>
</div>
<div id="hostlangconf" typeof="bibo:Chapter" about="#hostlangconf" class="section">
<h3><span class="secno">4.2 </span>RDFa Host Language Conformance</h3>
<p>Host Languages that incorporate RDFa must adhere to the following:</p>
<ul>
<li> All of the facilities required in this specification <em class="rfc2119" title="must">must</em> be
included in the Host Language.</li>
<li>The attributes defined in this specification <em class="rfc2119" title="must">must</em> be included in
the content model of the Host Language.</li>
<li> If the Host Language uses XML Namespaces [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-NAMES">XML-NAMES</a></cite>], the
attributes in this specification <em class="rfc2119" title="should">should</em> be defined in 'no
namespace'. (e.g., when the attributes are used on elements in the
Host Language's namespace, they can be used with no qualifying
prefix: <code>&lt;myml:myElement property=&quot;next&quot;&gt;</code>).
When a Host Language does not use the attributes in 'no namespace',
they <em class="rfc2119" title="must">must</em> be referenced via the XHTML Namespace (<code>http://www.w3.org/1999/xhtml</code>).</li>
<li>If the Host Language has its own definition for any attribute
defined in this specification, that definition <em class="rfc2119" title="must">must</em> be such that the
processing required by this specification remains possible when the
attribute is used in a way consistent with the requirements herein.</li>
<li>The Host Language <em class="rfc2119" title="may">may</em> specify an <a class="tref" title="initial-context" href="#T-initial-context">initial context</a>
(e.g., the definition of terms, IRI mappings, and/or a default
vocabulary IRI). Such an <a class="tref" title="initial-context" href="#T-initial-context">initial context</a> <em class="rfc2119" title="should">should</em> be
defined using the conventions defined in <a href="#s_initialcontexts">RDFa
Initial Contexts</a>.</li>
</ul>
</div>
<div id="xmlrdfaconformance" typeof="bibo:Chapter" about="#xmlrdfaconformance" class="section">
<h3><span class="secno">4.3 </span>XML+RDFa Document Conformance</h3>
<p>This specification does not define a stand-alone document type. The
attributes herein are intended to be integrated into other host
languages (e.g., HTML+RDFa or XHTML+RDFa). However, this specification
<strong>does</strong> define processing rules for generic XML
documents - that is, those documents delivered as media types <code>text/xml</code>
or <code>application/xml</code>. Such documents must meet all of the
following criteria:</p>
<ol>
<li>The document <em class="rfc2119" title="must">must</em> be well-formed as defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-XML10-4e">XML10-4e</a></cite>]. </li>
<li> The document <em class="rfc2119" title="must">must</em> use the attributes defined in this
specification through references to the XHTML namespace (<code>http://www.w3.org/1999/xhtml</code>).
</li>
</ol>
<p>When an RDFa Processor processes an XML+RDFa document, it does so via
the following <a class="tref" title="initial-context" href="#T-initial-context">initial context</a>:</p>
<ol>
<li>There are default terms (e.g., <code>describedby</code>, <code>license</code>, and <code>role</code>), defined
in <a href="http://www.w3.org/2011/rdfa-context/rdfa-1.1"><code>http://www.w3.org/2011/rdfa-context/rdfa-1.1</code></a>.</li>
<li>There are default prefix mappings (e.g., <code>dc</code>),
defined in <a href="http://www.w3.org/2011/rdfa-context/rdfa-1.1"><code>http://www.w3.org/2011/rdfa-context/rdfa-1.1</code></a>.</li>
<li>There is no default vocabulary IRI.</li>
<li>The <a class="tref" title="base" href="#T-base">base</a> can be set using the <span class="aref">@xml:base</span>
attribute as defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-XML10-4e">XML10-4e</a></cite>].</li>
<li>The <a class="tref" title="current-language" href="#T-current-language">current language</a> can be set using <span class="aref">@xml:lang</span>
attribute. </li>
</ol>
</div>
</div>
<div class="normative section" id="s_syntax" typeof="bibo:Chapter" about="#s_syntax">
<!-- OddPage -->
<h2><span class="secno">5. </span>Attributes and Syntax</h2>
<p>This specification defines a number of attributes and the way in which
the values of those attributes are to be interpreted when generating RDF
triples. This section defines the attributes and the syntax of their
values.</p>
<dl>
<dt><dfn class="adef" title="about" id="A-about">about</dfn></dt>
<dd>a <a class="datatype internalDFN" title="SafeCURIEorCURIEorIRI" href="#dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</a>, used for stating what the
data is about (a 'subject' in RDF terminology);</dd>
<dt><dfn class="adef" title="content" id="A-content">content</dfn> </dt>
<dd>a <code>CDATA</code> string, for supplying machine-readable content
for a literal (a 'plain literal object', in RDF terminology);</dd>
<dt><dfn class="adef" title="datatype" id="A-datatype">datatype</dfn></dt>
<dd>a <a class="datatype internalDFN" title="TERMorCURIEorAbsIRI" href="#dfn-termorcurieorabsiri">TERMorCURIEorAbsIRI</a> representing a datatype, to
express the datatype of a literal;</dd>
<dt><dfn class="adef" title="href" id="A-href">href</dfn></dt>
<dd>a traditionally navigable <a class="externalDFN" title="URI">URI</a> for expressing the
partner resource of a relationship (a 'resource object', in RDF
terminology);</dd>
<dt><dfn class="adef" title="prefix" id="A-prefix">prefix</dfn></dt>
<dd>a white space separated list of prefix-name IRI pairs of the form
<pre><a href="#P_prefix">NCName</a> ':' ' '+ xs:anyURI</pre>
</dd>
<dt><dfn class="adef" title="property" id="A-property">property</dfn></dt>
<dd>a white space separated list of <a class="datatype internalDFN" title="TERMorCURIEorAbsIRIs" href="#dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</a>,
used for expressing relationships between a subject and some literal
text (also a 'predicate');</dd>
<dt><dfn class="adef" title="rel" id="A-rel">rel</dfn></dt>
<dd>a white space separated list of <a class="datatype internalDFN" title="TERMorCURIEorAbsIRIs" href="#dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</a>,
used for expressing relationships between two resources ('predicates'
in RDF terminology);</dd>
<dt><dfn class="adef" title="resource" id="A-resource">resource</dfn></dt>
<dd>a <a class="datatype internalDFN" title="SafeCURIEorCURIEorIRI" href="#dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</a> for expressing the partner
resource of a relationship that is not intended to be navigable (e.g.,
a 'clickable' link) (also an 'object');</dd>
<dt><dfn class="adef" title="rev" id="A-rev">rev</dfn> </dt>
<dd>a white space separated list of <a class="datatype internalDFN" title="TERMorCURIEorAbsIRIs" href="#dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</a>,
used for expressing reverse relationships between two resources (also
'predicates');</dd>
<dt><dfn class="adef" title="src" id="A-src">src</dfn></dt>
<dd>a <a class="externalDFN" title="URI">URI</a> for expressing the partner resource of a
relationship when the resource is embedded (also a 'resource object');</dd>
<dt><dfn class="adef" title="typeof" id="A-typeof">typeof</dfn></dt>
<dd>a white space separated list of <a class="datatype internalDFN" title="TERMorCURIEorAbsIRIs" href="#dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</a>
that indicate the RDF type(s) to associate with a subject;</dd>
<dt><dfn class="adef" title="vocab" id="A-vocab">vocab</dfn></dt>
<dd>A <a class="externalDFN" title="URI">URI</a> that defines the mapping to use when a <a class="datatype internalDFN" title="TERM" href="#dfn-term">TERM</a>
is referenced in an attribute value. See <a href="#s_terms">General
Use of Terms in Attributes</a> and the <a href="#s_vocab_expansion">section
on Vocabulary Expansion</a>.</dd>
<dt><dfn class="adef" title="inlist" id="A-inlist">inlist</dfn></dt>
<dd>An attribute (value ignored) used to indicate that the object
associated with a <code>rel</code> or <code>property</code>
attribute on the same element is to be added to the list for that
predicate. Causes a list to be created if it does not already exist</dd>
</dl>
<div id="white_space" typeof="bibo:Chapter" about="#white_space" class="section">
<h3><span class="secno">5.1 </span>White space within attribute values</h3>
<p>Many attributes accept a white space separated list of tokens. This
specification defines white space as:</p>
<pre><span id="P_whitespace">whitespace</span> ::= (#x20 | #x9 | #xD | #xA)+
</pre>
<p id="C1" about="#C1" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-05-20#resolution_1" rel="bibo:affirmedBy">When
attributes accept a white space separated list of tokens, an RDFa
Processor <em class="rfc2119" title="must">must</em> ignore any leading or trailing white space.</p>
<p class="note">This definition is consistent with the definition found
in [<cite><a class="bibref" rel="biblioentry" href="#bib-XML10">XML10</a></cite>].</p>
</div>
</div>
<div class="normative section" id="s_curies" typeof="bibo:Chapter" about="#s_curies">
<!-- OddPage -->
<h2><span class="secno">6. </span>CURIE Syntax Definition</h2>
<p>The key component of RDF is the IRI, but these are usually long and
unwieldy. RDFa therefore supports a mechanism by which IRIs can be
abbreviated, called 'compact URI expressions' or simply, <dfn title="curie" id="T-curie">CURIEs</dfn>.</p>
<p> When expanded, the resulting IRI <em class="rfc2119" title="must">must</em> be a syntactically valid IRI
[<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>]. For a more detailed explanation see <a href="#s_curieprocessing">CURIE
and IRI Processing</a>. The <em>lexical space</em> of a CURIE is as
defined in <a href="#P_curie">curie</a> below. The <em>value space</em>
is the set of IRIs.</p>
<p>A CURIE is comprised of two components, a <em><dfn title="prefix" id="T-prefix">prefix</dfn></em>
and a <em><dfn title="reference" id="T-reference">reference</dfn></em>. The prefix is separated from the
reference by a colon (<code>:</code>). In general use it is possible to
omit the prefix, and so create a CURIE that makes use of the 'default
prefix' mapping; in RDFa the 'default prefix' mapping is <code>http://www.w3.org/1999/xhtml/vocab#</code>.
It's also possible to omit both the prefix <em>and</em> the colon, and
so create a CURIE that contains just a reference which makes use of the
'no prefix' mapping. This specification does not define a 'no prefix'
mapping. RDFa Host Languages <em class="rfc2119" title="must not">must not</em> define a 'no prefix' mapping. </p>
<p class="note"> The RDFa 'default prefix' should not be confused with the
'default namespace' as defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-NAMES">XML-NAMES</a></cite>]. An RDFa Processor <em class="rfc2119" title="must
not">must
not</em> treat an XML-NAMES 'default namespace' declaration as if it were
setting the 'default prefix'. </p>
<p> The general syntax of a CURIE can be summarized as follows: </p>
<pre><span id="P_prefix">prefix</span> ::= <a href="http://www.w3.org/TR/2009/REC-xml-names-20091208/#NT-NCName">NCName</a>
<span id="P_reference">reference</span> ::= irelative-ref (as defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>])
<span id="P_curie">curie ::= [ [ prefix ] ':' ] reference</span>
<span id="P_safe_curie">safe_curie ::= '[' [ [ prefix ] ':' ] reference ']'</span>
</pre>
<p class="note"> The production <code>safe_curie</code> is not required,
even in situations where an attribute value is permitted to be a CURIE
or an IRI: An IRI that uses a scheme that is not an in-scope mapping <em>cannot</em>
be confused with a CURIE. The concept of a safe_curie is retained for
backward compatibility. </p>
<p> In normal evaluation of CURIEs the following context information would
need to be provided:</p>
<ul>
<li>a set of mappings from prefixes to IRIs;</li>
<li>a mapping to use with the default prefix (for example, <code>:p</code>);</li>
<li>a mapping to use when there is no prefix (for example, <code>p</code>);</li>
<li>a mapping to use with the '_' prefix, which is used to generate
unique identifiers (for example, <code>_:p</code>). </li>
</ul>
<p> In RDFa these values are defined as follows:</p>
<ul>
<li>the <strong>set of mappings from prefixes to URIs</strong> is
provided by the current in-scope prefix declarations of the <a class="tref" title="current-element" href="#T-current-element">current
element</a> during parsing;</li>
<li>the <strong>mapping to use with the default prefix</strong> is the
current default prefix mapping;</li>
<li>the <strong>mapping to use when there is no prefix</strong> is not
defined;</li>
<li>the <strong>mapping to use with the '_' prefix</strong>, is not
explicitly stated, but since it is used to generate <a class="tref" title="bnode" href="#T-bnode">bnode</a>s,
its implementation needs to be compatible with the RDF definition and
rules in <a href="#s_blankNodes">Referencing Blank Nodes</a>. A
document <em class="rfc2119" title="should not">should not</em> define a mapping for the '_' prefix. A Conforming
RDFa Processor <em class="rfc2119" title="must">must</em> ignore any definition of a mapping for the '_'
prefix.</li>
</ul>
<p>A CURIE is a representation of a full IRI. The rules for determining
that IRI are:</p>
<ul>
<li>If a CURIE consists of an empty <code>prefix</code> and a <code>reference</code>,
the IRI is obtained by taking the current default prefix mapping and
concatenating it with the <code>reference</code>. If there is no
current default prefix mapping, then this is not a valid CURIE and
<em class="rfc2119" title="must">must</em> be ignored. </li>
<li>Otherwise, if a CURIE consists of a non-empty <code>prefix</code>
and <code>reference</code>, and if there is an in-scope mapping for <code>prefix</code>
(when compared case-insensitively), then the IRI is created by using
that mapping, and concatenating it with the <code>reference</code>. </li>
<li>Finally, if there is no in-scope mapping for <code>prefix</code>,
then the value is not a CURIE. </li>
</ul>
<p class="note">See <a href="#s_terms">General Use of Terms in Attributes</a>
for the way items with no colon can be interpreted in some datatypes by
RDFa Processors.</p>
<div class="informative section" id="why-curies-and-not-qnames" typeof="bibo:Chapter" about="#why-curies-and-not-qnames">
<h3><span class="secno">6.1 </span>Why CURIEs and not QNames?</h3><p><em>This section is non-normative.</em></p>
<p>In many cases, language designers have attempted to use QNames for an
extension mechanism [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>]. QNames do permit independent
management of the name collection, and <em>can</em> map the names to
a resource. Unfortunately, QNames are unsuitable in most cases because
1) the use of QName as identifiers in attribute values and element
content is problematic as discussed in [<cite><a class="bibref" rel="biblioentry" href="#bib-QNAMES">QNAMES</a></cite>] and 2) the syntax of
QNames is overly restrictive and does not allow all possible IRIs to
be expressed.</p>
<p>A specific example of the problem this causes comes from attempting
to define the name collection for books. In a QName, the part after
the colon must be a valid element name, making an example such as the
following <em>invalid</em>: <code>isbn:0321154991</code></p>
<p>This is not a valid QName simply because &quot;0321154991&quot; is not a valid
element name. Yet, in the example given, we don't really want to
define a valid element name anyway. The whole reason for using a QName
was to reference an item in a private scope - that of ISBNs. Moreover,
in this example, we want the names within that scope to map to an IRI
that will reveal the meaning of that ISBN. As you can see, the
definition of QNames and this (relatively common) use case are in
conflict with one another.</p>
<p>This specification addresses the problem by defining CURIEs.
Syntactically, CURIEs are a superset of QNames.</p>
<p>Note that this specification is targeted at language designers, not
document authors. Any language designer considering the use of QNames
as a way to represent IRIs or unique tokens should consider instead
using CURIEs:</p>
<ul>
<li>CURIEs are designed from the ground up to be used in attribute
values. QNames are designed for unambiguously naming elements and
attributes.</li>
<li>CURIEs expand to IRIs, and any IRI can be represented by such an
expansion. QNames are treated as value pairs, but even if those
pairs are combined into a string, only a subset of IRIs can be
represented.</li>
<li>CURIEs can be used in non-XML grammars, and can even be used in
XML languages that do not support XML Namespaces. QNames are limited
to XML Namespace-aware XML Applications.</li>
</ul>
</div>
</div>
<div class="normative section" id="s_model" typeof="bibo:Chapter" about="#s_model">
<!-- OddPage -->
<h2><span class="secno">7. </span>Processing Model</h2>
<p> This section looks at a generic set of processing rules for creating a
set of triples that represent the structured data present in an RDFa
document. Processing need not follow the DOM traversal technique
outlined here, although the effect of following some other manner of
processing must be the same as if the processing outlined here were
followed. The processing model is explained using the idea of DOM
traversal which makes it easier to describe (particularly in relation to
the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>). </p>
<div class="explanation">Note that in this section, explanations about the
processing model or guidance to implementors are enclosed in sections
like this.</div>
<div id="overview" typeof="bibo:Chapter" about="#overview" class="section">
<h3><span class="secno">7.1 </span>Overview</h3>
<p> Evaluating a document for RDFa triples is carried out by starting at
the document object, and then visiting each of its child elements in
turn, in document order, applying processing rules. Processing is
recursive in that for each child element the processor also visits
each of <em>its</em> child elements, and applies the same processing
rules. </p>
<p class="note"> In some environments there will be little difference
between starting at the root element of the document, and starting at
the document object itself. It is defined this way because in some
environments important information is present at the document object
level which is not present on the root element. </p>
<p> As processing continues, rules are applied which may generate
triples, and may also change the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>
information that will then be used when processing descendant
elements. </p>
<p class="note"> This specification does not say anything about what
should happen to the triples generated, or whether more triples might
be generated during processing than are outlined here. However, to be
conforming, an RDFa Processor <em class="rfc2119" title="must">must</em> act as if at a minimum the rules in
this section are applied, and a single <a class="tref" title="rdf-graph" href="#T-rdf-graph">RDF graph</a>
produced. As described in the <a href="#processorconf">RDFa Processor
Conformance</a> section, any additional triples generated <em class="rfc2119" title="must not">must not</em>
appear in the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>. </p>
</div>
<div id="evaluation-context" typeof="bibo:Chapter" about="#evaluation-context" class="section">
<h3><span class="secno">7.2 </span>Evaluation Context</h3>
<p> During processing, each rule is applied using information provided
by an <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>. An <dfn title="initial-context" id="T-initial-context">initial context</dfn>
is created when processing begins. That context has the following
members:</p>
<ul>
<li> The <dfn title="base" id="T-base">base</dfn>. This will usually be the IRI of the
document being processed, but it could be some other IRI, set by
some other mechanism, such as the (X)HTML <code>base</code>
element. The important thing is that it establishes an IRI against
which relative paths can be resolved. </li>
<li> The <dfn title="parent-subject" id="T-parent-subject">parent subject</dfn>. The initial
value will be the same as the initial value of <a class="tref" title="base" href="#T-base">base</a>,
but it will usually change during the course of processing. </li>
<li> The <dfn title="parent-object" id="T-parent-object">parent object</dfn>. In some
situations the object of a statement becomes the subject of any
nested statements, and this property is used to convey this value.
Note that this value may be a <a class="tref" title="bnode" href="#T-bnode">bnode</a>, since in some
situations a number of nested statements are grouped together on one
<a class="tref" title="bnode" href="#T-bnode">bnode</a>. This means that the <a class="tref" title="bnode" href="#T-bnode">bnode</a> must be
set in the containing statement and passed down, and this property
is used to convey this value. </li>
<li>A list of current, in-scope <dfn title="list-of-iri-mappings" id="T-list-of-iri-mappings">IRI
mappings</dfn>.</li>
<li>A list of <dfn title="incomplete-triple" id="T-incomplete-triple">incomplete triple</dfn>s. A triple can be
incomplete when no object resource is provided alongside a predicate
that requires a resource (i.e., <a class="aref" href="#A-rel" title="rel">@rel</a> or <a class="aref" href="#A-rev" title="rev">@rev</a>).
The triples can be completed when a resource becomes available,
which will be when the next subject is specified (part of the
process called <a class="tref" title="chaining" href="#T-chaining">chaining</a>).</li>
<li>A <dfn title="list-mapping" id="T-list-mapping">list mapping</dfn> mapping IRIs to lists.</li>
<li>The <dfn title="language" id="T-language">language</dfn>. Note that there is no default
language.</li>
<li>The <dfn title="term-mappings" id="T-term-mappings">term mappings</dfn>, a list of terms and their
associated IRIs. This specification does not define an initial list.
Host Languages <em class="rfc2119" title="may">may</em> define an initial list.</li>
<li>The <dfn title="default-vocabulary" id="T-default-vocabulary">default vocabulary</dfn>, a value to use as the prefix
IRI when a <a class="tref" title="term" href="#T-term">term</a> is used. This specification does not
define an initial setting for the default vocabulary. Host Languages
<em class="rfc2119" title="may">may</em> define an initial setting.</li>
</ul>
<p>During the course of processing, new <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>s
are created which are passed to each child element. The rules
described below will determine the values of the items in the context.
Additionally, some rules will cause new triples to be created by
combining information provided by an element with information from the
<a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>.</p>
<p>During the course of processing a number of locally scoped values are
needed, as follows:</p>
<ul>
<li>An initially empty list of <a class="tref" title="iri-mapping" href="#T-iri-mapping">IRI mapping</a>s, called the
<dfn title="local-list-of-iri-mappings" id="T-local-list-of-iri-mappings">local list of IRI mappings</dfn>.</li>
<li>An initially empty <dfn title="list-of-incomplete-triples" id="T-list-of-incomplete-triples">list of incomplete triples</dfn>,
called the <dfn title="local-list-of-incomplete-triples" id="T-local-list-of-incomplete-triples">local list of incomplete triples</dfn>.</li>
<li>An initially empty <a class="tref" title="language" href="#T-language">language</a> value.</li>
<!--
<li>A <tdef>recurse</tdef> flag. Processing generally continues recursively through the entire tree of elements available. However, if an author indicates that some branch of the tree should be treated as an XML literal, no further processing should take place on that branch, and setting this flag to <code>false</code> would have that effect. </li>
-->
<li> A <dfn title="skip-element" id="T-skip-element">skip element</dfn> flag, which indicates whether the <a class="tref" title="current-element" href="#T-current-element">current
element</a> can safely be ignored since it has no relevant RDFa
attributes. Note that descendant elements will still be processed. </li>
<li> A <dfn title="new-subject" id="T-new-subject">new subject</dfn> value, which once calculated will set
the <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> property in an <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a>, as well as being used to complete any <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete
triple</a>s, as described in the next section. </li>
<li> A value for the <dfn title="current-property-value" id="T-current-property-value">current
property value</dfn>, the literal to use when creating triples
that have a literal object, or IRI-s in the absence of <a class="aref" href="#A-rel" title="rel">@rel</a>
or <a class="aref" href="#A-rev" title="rev">@rev</a>. </li>
<li> A value for the <dfn title="current-object-resource" id="T-current-object-resource">current
object resource</dfn>, the resource to use when creating triples
that have a resource object. </li>
<li> A value for the <dfn title="typed-resource" id="T-typed-resource">typed resource</dfn>,
the source for creating <code>rdf:type</code> relationships to
types specified in <a class="aref" href="#A-datatype" title="datatype">@datatype</a>. </li>
<li> The <dfn title="local-term-mappings" id="T-local-term-mappings">local term mappings</dfn>, a list of terms and their
associated IRIs.</li>
<li> The <dfn title="local-list-mapping" id="T-local-list-mapping">local list mapping</dfn>, mapping IRIs to lists</li>
<li> A <dfn title="local-default-vocabulary" id="T-local-default-vocabulary">local default vocabulary</dfn>, an IRI to use as a
prefix mapping when a <a class="tref" title="term" href="#T-term">term</a> is used.</li>
</ul>
</div>
<div id="s_chaining" typeof="bibo:Chapter" about="#s_chaining" class="section">
<h3><span class="secno">7.3 </span>Chaining</h3>
<p>Statement <dfn title="chaining" id="T-chaining">chaining</dfn> is an RDFa feature that allows the
author to link RDF statements together while avoiding unnecessary
repetitive markup. For example, if an author were to add statements as
children of an object that was a resource, these statements should be
interpreted as being about that resource: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; <span class="hilite">resource=&quot;http://dbpedia.org/resource/German_Empire&quot;</span>&gt;
<span class="hilite">&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;</span>
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> In this example we can see that an object resource
('German_Empire'), has become the subject for nested statements. This
markup also illustrates the basic chaining pattern of 'A has a B has a
C' (i.e., Einstein has a birth place of the German Empire, which has a
long name of &quot;the German Empire&quot;). </p>
<p>It's also possible for the subject of nested statements to provide
the object for <em>containing</em> statements — essentially the
reverse of the example we have just seen. To illustrate, we'll take an
example of the type of chaining just described, and show how it could
be marked up more efficiently. To start, we mark up the fact that
Albert Einstein had, at some point in his life, a residence both in
the German Empire and in Switzerland: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
<span class="hilite">&lt;div rel=&quot;dbp-owl:residence&quot; resource=&quot;http://dbpedia.org/resource/German_Empire&quot;&gt;&lt;/div&gt;</span>
<span class="hilite">&lt;div rel=&quot;dbp-owl:residence&quot; resource=&quot;http://dbpedia.org/resource/Switzerland&quot;&gt;&lt;/div&gt;</span>
&lt;/div&gt;</pre>
<p>Now, we show the same information, but this time we create an <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete
triple</a> from the residence part, and then use any number of
further subjects to 'complete' that triple, as follows:</p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot; rel=&quot;dbp-owl:residence&quot;&gt;
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;&gt;&lt;/span&gt;</span>
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/Switzerland&quot;&gt;&lt;/span&gt;</span>
&lt;/div&gt;</pre>
<p> In this example, the <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a> actually gets
completed twice, once for the German Empire and once for Switzerland,
giving exactly the same information as we had in the earlier example:
</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
dbp-owl:residence &lt;http://dbpedia.org/resource/German_Empire&gt; .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
dbp-owl:residence &lt;http://dbpedia.org/resource/Switzerland&gt; .</pre>
<p> Chaining can sometimes involve elements containing relatively
minimal markup, for example showing only one resource, or only one
predicate. Here the <code>img</code> element is used to carry a
picture of Einstein: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;div <span class="hilite">rel=&quot;foaf:depiction&quot;</span>&gt;
&lt;img src=&quot;http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg&quot; /&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> When such minimal markup is used, any of the resource-related
attributes could act as a subject or an object in the chaining: </p>
<pre class="example">&lt;div <span class="hilite">about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;</span>&gt;
&lt;div <span class="hilite">rel=&quot;dbp-owl:residence&quot;</span>&gt;
&lt;span <span class="hilite">about=&quot;http://dbpedia.org/resource/German_Empire&quot;</span>&gt;&lt;/span&gt;
&lt;span <span class="hilite">about=&quot;http://dbpedia.org/resource/Switzerland&quot;</span>&gt;&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>Note that, as noted above, in many situations the <a class="aref" href="#A-property" title="property">@property</a>
and <a class="aref" href="#A-rel" title="rel">@rel</a> are interchangeable. This is <em>not</em> true
for chaining. Taking the first example, if that example was used as
follows:</p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div <span class="hilite">property=&quot;dbp:birthPlace&quot;</span> resource=&quot;http://dbpedia.org/resource/German_Empire&quot;&gt;
&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>The subject for the 'German Empire' would remain Albert Einstein (and
that would, of course, be an error). This is the main difference
between <a class="aref" href="#A-property" title="property">@property</a> and <a class="aref" href="#A-rel" title="rel">@rel</a>: the latter
induces chaining, whereas the former, usually, does not.</p>
</div>
<div id="s_curieprocessing" typeof="bibo:Chapter" about="#s_curieprocessing" class="section">
<h3><span class="secno">7.4 </span>CURIE and IRI Processing</h3>
<p> Since RDFa is ultimately a means for transporting RDF, a key concept
is the <em>resource</em> and its manifestation as a IRI. RDF deals
with complete IRIs (not relative paths); when converting RDFa to
triples, any relative IRIs <em class="rfc2119" title="must">must</em> be resolved relative to the base IRI,
using the algorithm defined in section 6.5 of RFC 3987 [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>], <em>Reference
Resolution</em>. The values of <a href="#s_syntax">RDFa attributes</a>
that refer to IRIs use three different datatypes: <a class="externalDFN" title="URI">URI</a>,
<a class="datatype internalDFN" title="SafeCURIEorCURIEorIRI" href="#dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</a>, or <a class="datatype internalDFN" title="TERMorCURIEorAbsIRI" href="#dfn-termorcurieorabsiri">TERMorCURIEorAbsIRI</a>.
All these attributes are mapped, after processing, to IRIs. The
handling of these attributes is as follows:</p>
<dl>
<dt>URI</dt>
<dd>The content is a URI, and is used as such.</dd>
<dt>SafeCURIEorCURIEorIRI</dt>
<dd>
<ul>
<li>When the value is surrounded by square brackets, then the
content within the brackets is evaluated as a CURIE according to
the <a href="#s_curies">CURIE Syntax definition</a>. If it is
not a valid CURIE, the value <em class="rfc2119" title="must">must</em> be ignored.</li>
<li>Otherwise, the value is evaluated as a CURIE. If it is a valid
CURIE, the resulting IRI is used; otherwise, the value is
processed as an IRI. </li>
</ul>
</dd>
<dt>TERMorCURIEorAbsIRI</dt>
<dd>
<ul id="C2" about="#C2" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-01#resolution_3" rel="bibo:affirmedBy">
<li>If the value is an <a class="tref" title="term" href="#T-term">term</a>
then it is evaluated as a term according to <a href="#s_terms">General Use of Terms in Attributes</a>. Note that this step may mean
that the value is to be ignored.</li>
<li>If the value is a valid CURIE, then the resulting IRI is used.</li>
<li>If the value is an absolute IRI, that value is used.</li>
<li>Otherwise, the value is ignored.</li>
</ul>
</dd>
</dl>
<p id="C3" about="#C3" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-05-20#resolution_2" rel="bibo:affirmedBy">Note
that it is possible for all values in an attribute to be ignored. When
that happens, the attribute <em class="rfc2119" title="must">must</em> be treated as if it were empty.</p>
<p>For example, the full IRI for Albert Einstein on DBPedia is:</p>
<pre class="example">http://dbpedia.org/resource/Albert_Einstein</pre>
<p>This can be shortened by authors to make the information easier to
manage, using a CURIE. The first step is for the author to create a
prefix mapping that links a prefix to some leading segment of the IRI.
In RDFa these mappings are expressed using the XML namespace syntax:</p>
<pre class="example">&lt;div <span class="hilite">prefix=&quot;db: http://dbpedia.org/&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p>Once the prefix has been established, an author can then use it to
shorten an IRI as follows:</p>
<pre class="example">&lt;div prefix=&quot;db: http://dbpedia.org/&quot;&gt;
&lt;div about=&quot;<span class="hilite">db:resource/Albert_Einstein</span>&quot;&gt;
...
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> The author is free to split the IRI at any point, as long as it
begins at the left end. However, since a common use of CURIEs is to
make available libraries of terms and values, the prefix will usually
be mapped to some common segment that provides the most re-use, often
provided by those who manage the library of terms. For example, since
DBPedia contains an enormous list of resources, it is more efficient
to create a prefix mapping that uses the base location of the
resources:</p>
<pre class="example">&lt;div <span class="hilite">prefix=&quot;dbr: http://dbpedia.org/resource/&quot;</span>&gt;
&lt;div about=&quot;<span class="hilite">dbr:Albert_Einstein</span>&quot;&gt;
...
&lt;/div&gt;
&lt;div about=&quot;<span class="hilite">dbr:Baruch_Spinoza</span>&quot;&gt;
...
&lt;/div&gt;
&lt;/div&gt;</pre>
<div class="explanation"> Note that it is generally considered a bad
idea to use relative paths in prefix declarations. Since it is
possible that an author may ignore this guidance, it is further
possible that the IRI obtained from a CURIE is relative. However,
since all IRIs must be resolved relative to <a class="tref" title="base" href="#T-base">base</a> before
being used to create triples, the use of relative paths should not
have any effect on processing. </div>
<div id="scoping-of-prefix-mappings" typeof="bibo:Chapter" about="#scoping-of-prefix-mappings" class="section">
<h4><span class="secno">7.4.1 </span>Scoping of Prefix Mappings</h4>
<p>CURIE prefix mappings are defined on the current element and its
descendants. The inner-most mapping for a given prefix takes
precedence. For example, the IRIs expressed by the following two
CURIEs are different, despite the common prefix, because the prefix
mappings are locally scoped: </p>
<pre class="example">&lt;div <span class="hilite">prefix=&quot;dbr: http://dbpedia.org/resource/&quot;</span>&gt;
&lt;div about=&quot;<span class="hilite">dbr:Albert_Einstein</span>&quot;&gt;
...
&lt;/div&gt;
&lt;/div&gt;
&lt;div <span class="hilite">prefix=&quot;dbr: http://someotherdb.org/resource/&quot;</span>&gt;
&lt;div about=&quot;<span class="hilite">dbr:Albert_Einstein</span>&quot;&gt;
...
&lt;/div&gt;
&lt;/div&gt;</pre> </div>
<div id="general-use-of-curies-in-attributes" typeof="bibo:Chapter" about="#general-use-of-curies-in-attributes" class="section">
<h4><span class="secno">7.4.2 </span>General Use of CURIEs in Attributes</h4>
<p> There are a number of ways that attributes make use of CURIEs, and
they need to be dealt with differently. These are: </p>
<ol>
<li>An attribute may allow one or more values that are a mixture of
TERMs, CURIEs, and absolute IRIs.</li>
<li>An attribute may allow one or more values that are a mixture of
CURIEs and IRIs. In this case any value that is not a CURIE, as
outlined in section <a href="#s_curies">CURIE Syntax Definition</a>,
will be processed as an IRI.</li>
<li>If the value <em>is</em> surrounded by square brackets, then
the content within the brackets is always evaluated according to
the rules in <a href="#s_curies">CURIE Syntax Definition</a> -
and if that content is not a CURIE, then the content <em class="rfc2119" title="must">must</em> be
ignored.</li>
</ol>
<p class="note">An empty attribute value (e.g., <code>typeof=''</code>)
is <em>still </em> a CURIE, and is processed as such. The rules
for this processing are defined in <a href="#s_sequence">Sequence</a>.
Specifically, however, an empty attribute value is <em>never</em>
treated as a relative IRI by this specification.</p>
<p>An example of an attribute that can contain a CURIEorIRI is <a class="aref" href="#A-about" title="about">@about</a>.
To express an IRI directly, an author might do this:</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p>whilst to express the IRI above as a CURIE they would do this:</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;dbr:Albert_Einstein&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p>The author could also use a safe CURIE, as follows:</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;[dbr:Albert_Einstein]&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p> Since non-CURIE values <em class="rfc2119" title="must">must</em> be ignored, the following value in <a class="aref" href="#A-about" title="about">@about</a>
would <em>not</em> set a new subject, since <a class="aref" href="#A-about" title="about">@about</a>
does not permit the use of <a class="datatype internalDFN" title="TERM" href="#dfn-term">TERM</a>s, and the CURIE
has no prefix separator.</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;[Albert_Einstein]&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p>However, this markup <em>would</em> set a subject, since it is not
a CURIE, but a valid relative IRI:</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;Albert_Einstein&quot;</span>&gt;
...
&lt;/div&gt;</pre>
<p>
Note that several RDFa attributes are able to also take <a class="datatype internalDFN" title="term" href="#dfn-term">TERMS</a> as their value.
This is discussed in the next section.
</p>
</div>
<div id="s_terms" typeof="bibo:Chapter" about="#s_terms" class="section">
<h4><span class="secno">7.4.3 </span>General Use of Terms in Attributes</h4>
<p>Some RDFa attributes have a datatype that permits a <dfn title="term" id="T-term">term</dfn> to be referenced.
RDFa defines the syntax of a term as:</p>
<pre><span id="P_term">term ::= <a href="http://www.w3.org/TR/2006/REC-xml-names-20060816/#NT-NCNameStartChar">NCNameStartChar</a> <a href="#P_termChar">termChar</a>*</span>
<span id="P_termChar">termChar ::= ( <a href="http://www.w3.org/TR/2006/REC-xml-names-20060816/#NT-NCNameChar">NameChar</a> - ':' ) | '/'</span>
</pre>
<p class="note">For the avoidance of doubt, this definition
means a 'term' in RDFa is an XML <a href="http://www.w3.org/TR/2006/REC-xml-names-20060816/#NT-NCName">NCName</a> that also permits
slash as a non-leading character.</p>
<p>When an RDFa attribute permits the use of a term, and the value
being evaluated matches the production for term above, it is
transformed to an IRI using the following logic:</p>
<ul>
<li>Check if the <code>term</code> matches an item in the list of <a class="tref" title="local-term-mappings" href="#T-local-term-mappings">local
term mappings</a>. First compare against the list <em>case-sensitively</em>,
and if there is no match then compare <em>case-insensitively</em>.
If there is a match, use the associated IRI.</li>
<li>If there is a <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local default vocabulary</a> the IRI is
obtained by concatenating that value and the <code>term</code>.</li>
<li>If there is no <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local default vocabulary</a>, the <code>term</code>
has no associated IRI and <em class="rfc2119" title="must">must</em> be ignored.</li>
</ul>
<!-- <p class='note' id="C22" about="#C22" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-01-20#ISSUE__2d_63__3a__Case__2d_insensitive_term_matching" rel='bibo:affirmedBy'>In the event that multiple <code>term</code>s are defined that differ only in case (e.g., 'Agent', 'agent', and 'AGENT'), if a reference is made which DOES NOT match case-sensitively (e.g., typeof='AGENt'), the results are UNSPECIFIED.</p> -->
</div>
<div id="use-of-curies-in-specific-attributes" typeof="bibo:Chapter" about="#use-of-curies-in-specific-attributes" class="section">
<h4><span class="secno">7.4.4 </span>Use of CURIEs in Specific Attributes</h4>
<p> The general rules discussed in the previous sections apply to the
RDFa attributes in the following ways: </p>
<ul>
<li><a class="aref" href="#A-about" title="about">@about</a> and <a class="aref" href="#A-resource" title="resource">@resource</a> support the
datatype <a class="datatype internalDFN" title="SafeCURIEorCURIEorIRI" href="#dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</a> - allowing a
SafeCURIE, a CURIE, or an IRI.</li>
<li><a class="aref" href="#A-href" title="href">@href</a> and <a class="aref" href="#A-src" title="src">@src</a> are as defined in the
Host Language (e.g., XHTML), and support only an IRI.</li>
<li><a class="aref" href="#A-vocab" title="vocab">@vocab</a> supports an IRI.</li>
<li><a class="aref" href="#A-datatype" title="datatype">@datatype</a> supports the datatype <a class="datatype internalDFN" title="TERMorCURIEorAbsIRI" href="#dfn-termorcurieorabsiri">TERMorCURIEorAbsIRI</a>
- allowing a single Term, CURIE, or Absolute IRI.</li>
<li><a class="aref" href="#A-property" title="property">@property</a>, <a class="aref" href="#A-typeof" title="typeof">@typeof</a>, <a class="aref" href="#A-rel" title="rel">@rel</a>,
and <a class="aref" href="#A-rev" title="rev">@rev</a> support the datatype <a class="datatype internalDFN" title="TERMorCURIEorAbsIRIs" href="#dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</a>
- allowing one or more Terms, CURIEs, or Absolute IRIs.</li>
</ul>
<p> Any value that matches a defined term <em class="rfc2119" title="must">must</em> be expanded into a
reference to the corresponding IRI. For example in [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>]
the following examples: </p>
<pre class="example">&lt;link rel=&quot;<span class="hilite">next</span>&quot; href=&quot;http://example.org/page2.html&quot; /&gt;
&lt;link rel=&quot;<span class="hilite">xhv:next</span>&quot; href=&quot;http://example.org/page2.html&quot; /&gt;</pre>
<p>would each generate the following triple:</p>
<pre class="example">&lt;&gt; &lt;http://www.w3.org/1999/xhtml/vocab#next&gt; &lt;http://example.org/page2.html&gt; .</pre> </div>
<div id="s_blankNodes" typeof="bibo:Chapter" about="#s_blankNodes" class="section">
<h4><span class="secno">7.4.5 </span>Referencing Blank Nodes</h4>
<p>In RDFa, it is possible to establish relationships using various
types of resource references, including <a class="tref" title="bnode" href="#T-bnode">bnode</a>s. If a
subject or object is defined using a CURIE, and that CURIE
explicitly names a <a class="tref" title="bnode" href="#T-bnode">bnode</a>, then a Conforming Processor
<em class="rfc2119" title="must">must</em> create the <a class="tref" title="bnode" href="#T-bnode">bnode</a> when it is encountered during
parsing. The RDFa Processor <em class="rfc2119" title="must">must</em> also ensure that no <a class="tref" title="bnode" href="#T-bnode">bnode</a>
created automatically (as a result of <a class="tref" title="chaining" href="#T-chaining">chaining</a>) has a
name that collides with a <a class="tref" title="bnode" href="#T-bnode">bnode</a> that is defined by
explicit reference in a CURIE.</p>
<p>Consider the following example:</p>
<pre class="example">&lt;link <span class="hilite">about=&quot;_:john&quot;</span> rel=&quot;foaf:mbox&quot;
href=&quot;mailto:john@example.org&quot; /&gt;
&lt;link <span class="hilite">about=&quot;_:sue&quot;</span> rel=&quot;foaf:mbox&quot;
href=&quot;mailto:sue@example.org&quot; /&gt;
&lt;link <span class="hilite">about=&quot;_:john&quot;</span> rel=&quot;foaf:knows&quot;
resource=&quot;_:sue&quot; /&gt;</pre>
<p>In the above fragment, two <a class="tref" title="bnode" href="#T-bnode">bnodes</a> are
explicitly created as the subject of triples. Those <a class="tref" title="bnode" href="#T-bnode">bnodes</a>
are then referenced to demonstrate the relationship between the
parties. After processing, the following triples will be generated:</p>
<pre class="example">_:john foaf:mbox &lt;mailto:john@example.org&gt; .
_:sue foaf:mbox &lt;mailto:sue@example.org&gt; .
_:john foaf:knows _:sue .</pre>
<p class="note" id="C18" about="#C18" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-10-21#resolution_3" rel="bibo:affirmedBy">
RDFa Processors use, internally, implementation-dependent
identifiers for bnodes. When triples are <em>retrieved</em>, new
bnode indentifiers are used, which usually bear no relation to the
original identifiers. However, implementations do ensure that these
generated bnode identifiers are consistent: each bnode will have its
own identifier, all references to a particular bnode will use the
same identifier, and different bnodes will have different
identifiers. </p>
<p>As a special case, <code>_:</code> is also a valid reference for <em>one</em>
specific <a class="tref" title="bnode" href="#T-bnode">bnode</a>.</p>
</div>
</div>
<div id="s_sequence" typeof="bibo:Chapter" about="#s_sequence" class="section">
<h3><span class="secno">7.5 </span>Sequence</h3>
<p> Processing would normally begin after the document to be parsed has
been completely loaded. However, there is no requirement for this to
be the case, and it is certainly possible to use a stream-based
approach, such as SAX [<cite><a class="bibref" rel="biblioentry" href="#bib-SAX">SAX</a></cite>] to extract the RDFa information.
However, if some approach other than the DOM traversal technique
defined here is used, it is important to ensure that Host
Language-specific processing rules are applied (e.g., XHTML+RDFa
[<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>] indicates the <code>base</code> element can be used,
and <code>base</code> will affect the interpretation of IRIs in <code>meta</code>
or <code>link</code> elements even if those elements are before the <code>base</code>
element in the stream). </p>
<p id="PS-initial-context"> At the beginning of processing, an initial <dfn title="evaluation-context" id="T-evaluation-context">evaluation
context</dfn> is created, as follows:</p>
<ul>
<li>the <a class="tref" title="base" href="#T-base">base</a> is set to the IRI of the document (or
another value specified in a language specific manner such as the
HTML <code>base</code> element); </li>
<li>the <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> is set to the <a class="tref" title="base" href="#T-base">base</a>
value;</li>
<li>the <a class="tref" title="parent-object" href="#T-parent-object">parent object</a> is set to null;</li>
<li>the <a class="tref" title="list-of-incomplete-triples" href="#T-list-of-incomplete-triples">list of incomplete triples</a> is empty;</li>
<li>the <a class="tref" title="list-mapping" href="#T-list-mapping">list mapping</a> is empty;</li>
<li>the <a class="tref" title="language" href="#T-language">language</a> is set to null.</li>
<li id="C12" about="#C12" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-22#resolution_2" rel="bibo:affirmedBy">
the <a class="tref" title="list-of-iri-mappings" href="#T-list-of-iri-mappings">list of IRI mappings</a> is empty (or a list defined
in the <a href="#s_initialcontexts">initial context</a> of the Host
Language).</li>
<li id="C13" about="#C13" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-22#resolution_2" rel="bibo:affirmedBy">the
<a class="tref" title="term-mappings" href="#T-term-mappings">term mappings</a> is set to null (or a list defined in the
<a href="#s_initialcontexts">initial context</a> of the Host
Language).</li>
<li id="C14" about="#C14" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-22#resolution_2" rel="bibo:affirmedBy">the
<a class="tref" title="default-vocabulary" href="#T-default-vocabulary">default vocabulary</a> is set to null (or a IRI defined in
the <a href="#s_initialcontexts">initial context</a> of the Host
Language).</li>
</ul>
<p> Processing begins by applying the processing rules below to the
document object, in the context of this initial <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a>. All elements in the tree are also processed
according to the rules described below, depth-first, although the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a> used for each set of rules will be based on previous
rules that may have been applied.</p>
<p class="note">This specification defines processing rules for optional
attributes that may not be present in all Host Languages (e.g., <code>@xmlns:</code>).
If these attributes are not supported in the Host Language, then the
corresponding processing rules are not relevant for that language.</p>
<p> The processing rules are:</p>
<ol>
<li id="PS-initialization"> First, the local values are initialized,
as follows:
<ul>
<!-- <li>the <tref>recurse</tref> flag is set to 'true';</li> -->
<li>the <a class="tref" title="skip-element" href="#T-skip-element">skip element</a> flag is set to 'false';</li>
<li><a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to null;</li>
<li><a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a> is set to null;</li>
<li><a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a> is set to null;</li>
<li>the <a class="tref" title="local-list-of-iri-mappings" href="#T-local-list-of-iri-mappings">local list of IRI mappings</a> is set to the
list of IRI mappings from the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>;</li>
<li>the <a class="tref" title="local-list-of-incomplete-triples" href="#T-local-list-of-incomplete-triples">local list of incomplete triples</a> is set to
null;</li>
<li>the <a class="tref" title="list-mapping" href="#T-list-mapping">list mapping</a> is set to (a reference of) the
list mapping from the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>;</li>
<li>the <a class="tref" title="current-language" href="#T-current-language">current language</a> value is set to the <a class="tref" title="language" href="#T-language">language</a>
value from the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>.</li>
<li>the <a class="tref" title="local-term-mappings" href="#T-local-term-mappings">local term mappings</a> is set to the <a class="tref" title="term-mappings" href="#T-term-mappings">term
mappings</a> from the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>.</li>
<li>the <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local default vocabulary</a> is set to the <a class="tref" title="default-vocabulary" href="#T-default-vocabulary">default
vocabulary</a> from the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>.</li>
</ul>
<div class="explanation"> Note that some of the local variables are
temporary containers for values that will be passed to descendant
elements via an <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>. In some cases
the containers will have the same name, so to make it clear which
is being acted upon in the following steps, the local version of
an item will generally be referred to as such. </div>
</li>
<li id="PS-default-vocabulary"> Next the <dfn title="current-element" id="T-current-element">current element</dfn>
is examined for any change to the <a class="tref" title="default-vocabulary" href="#T-default-vocabulary">default vocabulary</a>
via <a class="aref" href="#A-vocab" title="vocab">@vocab</a>. If <a class="aref" href="#A-vocab" title="vocab">@vocab</a> is present and
contains a value, its value updates the <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local default
vocabulary</a>. If the value is empty, then the <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local
default vocabulary</a> <em class="rfc2119" title="must">must</em> be reset to the Host Language
defined default (if any).
<div class="explanation"> The value of <a class="aref" href="#A-vocab" title="vocab">@vocab</a> is used
to generate a triple as follows:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="base" href="#T-base">base</a></dd>
<dt>predicate</dt>
<dd><code>http://www.w3.org/ns/rdfa#usesVocabulary</code></dd>
<dt>object</dt>
<dd>value from <a class="aref" href="#A-vocab" title="vocab">@vocab</a></dd>
</dl>
</div>
<div class="explanation"> A Host Language is not required to define
a default vocabulary. In such a case, setting <a class="aref" href="#A-vocab" title="vocab">@vocab</a>
to the empty value has the effect of clearing the <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local
default vocabulary</a>. </div>
</li>
<li id="PS-IRI-mappings">Next, the <a class="tref" title="current-element" href="#T-current-element">current element</a> is
examined for <dfn title="iri-mapping" id="T-iri-mapping">IRI mapping</dfn>s and these are added to the <a class="tref" title="local-list-of-iri-mappings" href="#T-local-list-of-iri-mappings">local
list of IRI mappings</a>. Note that a <a class="tref" title="iri-mapping" href="#T-iri-mapping">IRI mapping</a>
will simply overwrite any current mapping in the list that has the
same name;
<div class="explanation"> Mappings are defined via <a class="aref" href="#A-prefix" title="prefix">@prefix</a>.
<span id="C21" about="#C21" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-01-13#ISSUE__2d_62__3a____40_prefix_processing_order" rel="bibo:affirmedBy">Values
in this attribute are evaluated from beginning to end (e.g.,
left to right in typical documents).</span> <span id="C23" about="#C23" rel="bibo:affirmedBy" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-02-14#resolution_3">For
backward compatibility, RDFa Processors <em class="rfc2119" title="should">should</em> also permit the
definition of mappings via <span class="aref">@xmlns</span>. In
this case, the value to be mapped is set by the XML namespace
prefix, and the value to map is the value of the attribute — an
IRI. (Note that prefix mapping via <span class="aref">@xmlns</span>
is deprecated, and may be removed in a future version of this
specification.)</span> When <span class="aref">xmlns</span> is
supported, such mappings <em class="rfc2119" title="must">must</em> be processed before processing an
mappings from <a class="aref" href="#A-prefix" title="prefix">@prefix</a> on the same element. <span id="C5" about="#C5" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-05-13#resolution_1" rel="bibo:affirmedBy">
Regardless of how the mapping is declared, the value to be
mapped <em class="rfc2119" title="must">must</em> be converted to lower case</span>, and the IRI is
not processed in any way; in particular if it is a relative path
it <em class="rfc2119" title="must not">must not</em> be resolved against the current <a class="tref" title="base" href="#T-base">base</a>.
Authors <em class="rfc2119" title="should not">should not</em> use relative paths as the IRI. </div>
</li>
<li id="PS-language" about="#PS-language" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-05-13#resolution_3" rel="bibo:affirmedBy">
The <a class="tref" title="current-element" href="#T-current-element">current element</a> is also parsed for any language
information, and if present, <a class="tref" title="current-language" href="#T-current-language">current language</a> is set
accordingly;
<div class="explanation"> Host Languages that incorporate RDFa <em class="rfc2119" title="may">may</em>
provide a mechanism for specifying the natural language of an
element and its contents (e.g., XML provides the general-purpose
XML attribute <span class="aref">@xml:lang</span>). </div>
</li>
<li id="PS-new-subject"> If the <a class="tref" title="current-element" href="#T-current-element">current element</a> contains
no <a class="aref" href="#A-rel" title="rel">@rel</a> or <a class="aref" href="#A-rev" title="rev">@rev</a> attribute, then the next
step is to establish a value for <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>. This
step has two possible alternatives.
<ol>
<li id="GK1" about="#GK1" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
If the <a class="tref" title="current-element" href="#T-current-element">current element</a> contains the <a class="aref" href="#A-property" title="property">@property</a>
attribute, but does <em>not</em> contains neither the <a class="aref" href="#A-content" title="content">@content</a>
nor <a class="aref" href="#A-datatype" title="datatype">@datatype</a> attributes, then
<div class="explanation"> <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to
the IRI obtained from the first match from the following rule:
<ul>
<li>by using the IRI from <a class="aref" href="#A-about" title="about">@about</a>, if present,
obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>;</li>
</ul>
<p>If no IRI is provided by a resource attribute, then the
first match from the following rules will apply:</p>
<ul>
<li>if the element is the root element of the document, then
act as if there is an empty <a class="aref" href="#A-about" title="about">@about</a> present,
and process it according to the rule for <a class="aref" href="#A-about" title="about">@about</a>,
above;</li>
<li><em>otherwise</em>, if <a class="tref" title="parent-object" href="#T-parent-object">parent object</a> is
present, <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to the value of
<a class="tref" title="parent-object" href="#T-parent-object">parent object</a>.</li>
</ul>
<p>If <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present:</p>
<ul>
<li>if the element contains a <a class="aref" href="#A-href" title="href">@href</a>, <a class="aref" href="#A-src" title="src">@src</a>,
or <a class="aref" href="#A-resource" title="resource">@resource</a> attribute, the value of <a class="tref" title="typed-resource" href="#T-typed-resource">typed
resource</a> is set the IRI from the first value from
this set of attributes, obtained according to the section
on <a href="#s_curieprocessing">CURIE and IRI Processing</a>;</li>
<li>otherwise, the value of <a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a> is
set to a newly created <a class="tref" title="bnode" href="#T-bnode">bnode</a></li>
<li>The value of the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a>
is set to the value of <a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a></li>
</ul>
</div>
</li>
<li><em>otherwise</em>:
<div class="explanation">
<p>if the element contains a <a class="aref" href="#A-about" title="about">@about</a>, <a class="aref" href="#A-href" title="href">@href</a>,
<a class="aref" href="#A-src" title="src">@src</a>, or <a class="aref" href="#A-resource" title="resource">@resource</a> attribute, <a class="tref" title="new-subject" href="#T-new-subject">new
subject</a> is set to the IRI obtained from the first
value from this set of attributes, obtained according to the
section on <a href="#s_curieprocessing">CURIE and IRI
Processing</a>.</p>
<p>If no IRI is provided by a resource attribute, then the
first match from the following rules will apply:</p>
<ul>
<li>if the element is the root element of the document, then
act as if there is an empty <a class="aref" href="#A-about" title="about">@about</a> present,
and process it according to the rule for <a class="aref" href="#A-about" title="about">@about</a>,
above;</li>
<li>if <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present, then <a class="tref" title="new-subject" href="#T-new-subject">new
subject</a> is set to be a newly created <a class="tref" title="bnode" href="#T-bnode">bnode</a>.</li>
<li><em>otherwise</em>, if <a class="tref" title="parent-object" href="#T-parent-object">parent object</a> is
present, <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to the value of
<a class="tref" title="parent-object" href="#T-parent-object">parent object</a>. Additionally, if <a class="aref" href="#A-property" title="property">@property</a>
is <em>not</em> present then the <a class="tref" title="skip-element" href="#T-skip-element">skip element</a>
flag is set to 'true';</li>
</ul>
<p id="GK2" about="#GK2" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">if
<a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present, set the <a class="tref" title="typed-resource" href="#T-typed-resource">typed
resource</a> to the value of <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>.</p>
</div>
</li>
</ol>
</li>
<li id="PS-new-subject-and-object"> If the <a class="tref" title="current-element" href="#T-current-element">current element</a>
<em>does</em> contain a <a class="aref" href="#A-rel" title="rel">@rel</a> or <a class="aref" href="#A-rev" title="rev">@rev</a>
attribute, then the next step is to establish <em>both</em> a value
for <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> and a value for <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object
resource</a>:
<div class="explanation"> <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to the
IRI obtained from the first match from the following rules:
<ul>
<li>by using the IRI from <a class="aref" href="#A-about" title="about">@about</a>, if present,
obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>;</li>
</ul>
<p id="GK3" about="#GK3" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
if the <a class="aref" href="#A-typeof" title="typeof">@typeof</a> attribute is present, set <a class="tref" title="typed-resource" href="#T-typed-resource">typed
resource</a> to <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>.</p>
<p>If no IRI is provided then the first match from the following
rules will apply:</p>
<ul>
<li>if the element is the root element of the document then act
as if there is an empty <a class="aref" href="#A-about" title="about">@about</a> present, and
process it according to the rule for <a class="aref" href="#A-about" title="about">@about</a>,
above;</li>
<li><em>otherwise</em>, if <a class="tref" title="parent-object" href="#T-parent-object">parent object</a> is
present, <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> is set to that.</li>
</ul>
<p>Then the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a> is set to the
IRI obtained from the first match from the following rules:</p>
<ul>
<li>by using the IRI from <a class="aref" href="#A-resource" title="resource">@resource</a>, if present,
obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>;</li>
<li><em>otherwise</em>, by using the URI from <a class="aref" href="#A-href" title="href">@href</a>,
if present, obtained according to the section on <a href="#s_curieprocessing">CURIE
and URI Processing</a>.</li>
<li><em>otherwise</em>, by using the IRI from <a class="aref" href="#A-src" title="src">@src</a>,
if present, obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>.</li>
<li><em>otherwise</em>, if <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present and <a class="aref" href="#A-about" title="about">@about</a>
is not, use a newly created <a class="tref" title="bnode" href="#T-bnode">bnode</a>.</li>
</ul>
<p id="GK4" about="#GK4" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
If <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present and <a class="aref" href="#A-about" title="about">@about</a> is
not, set <a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a> to <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object
resource</a>.</p>
<p>Note that final value of the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a>
will either be null (from initialization) or a full IRI.</p>
</div>
</li>
<li id="PS-subject-types" about="#PS-subject-types" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
If in any of the previous steps a <a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a> was
set to a non-null value, it is now used to provide a subject for
type values;
<div class="explanation"> One or more 'types' for the <a class="tref" title="typed-resource" href="#T-typed-resource">typed
resource</a> can be set by using <a class="aref" href="#A-typeof" title="typeof">@typeof</a>. If
present, the attribute may contain one or more IRIs, obtained
according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>, each of which is used to generate a
triple as follows:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a></dd>
<dt>predicate</dt>
<dd>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</dd>
<dt>object</dt>
<dd>full IRI of 'type'</dd>
</dl>
</div>
</li>
<li id="PS-empty-list-mapping"> If in any of the previous steps a <a class="tref" title="new-subject" href="#T-new-subject">new
subject</a> was set to a non-null value <em>different</em>
from the <a class="tref" title="parent-object" href="#T-parent-object">parent object</a>;
<div class="explanation"> The <a class="tref" title="list-mapping" href="#T-list-mapping">list mapping</a> taken from
the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a> is set to a new, empty
mapping. </div>
</li>
<li id="PS-generate-triples"> If in any of the previous steps a <a class="tref" title="current-object-resource" href="#T-current-object-resource">current
object resource</a> was set to a non-null value, it is now used
to generate triples and add entries to the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a>:
<div class="explanation"> If the element contains <em>both</em> the
<a class="aref" href="#A-inlist" title="inlist">@inlist</a> and the <a class="aref" href="#A-rel" title="rel">@rel</a> attributes: the <a class="aref" href="#A-rel" title="rel">@rel</a>
may contain one or more IRIs, obtained according to the section on
<a href="#s_curieprocessing">CURIE and IRI Processing</a> each of
which is used to add an entry to the <a class="tref" title="list-mapping" href="#T-list-mapping">list mapping</a> as
follows:
<ul>
<li>if the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a> does not contain a
list associated with the IRI, instantiate a new list and add
to local list mappings</li>
<li>add the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a> to the list
associated with the IRI in the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a></li>
</ul>
</div>
<div class="explanation"> Predicates for the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object
resource</a> can be set by using one or both of the <a class="aref" href="#A-rel" title="rel">@rel</a>
and the <a class="aref" href="#A-rev" title="rev">@rev</a> attributes but, in case of the <a class="aref" href="#A-rel" title="rel">@rel</a>
attribute, only if the <a class="aref" href="#A-inlist" title="inlist">@inlist</a> is <em>not</em>
present:
<ul>
<li> If present, <a class="aref" href="#A-rel" title="rel">@rel</a> may contain one or more IRIs,
obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a> each of which is used to generate a
triple as follows:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="new-subject" href="#T-new-subject">new subject</a></dd>
<dt>predicate</dt>
<dd>full IRI</dd>
<dt>object</dt>
<dd><a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a></dd>
</dl>
</li>
<li> If present, <a class="aref" href="#A-rev" title="rev">@rev</a> may contain one or more IRIs,
obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a> each of which is used to generate a
triple as follows:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a></dd>
<dt>predicate</dt>
<dd>full IRI</dd>
<dt>object</dt>
<dd><a class="tref" title="new-subject" href="#T-new-subject">new subject</a></dd>
</dl>
</li>
</ul>
</div>
</li>
<li id="PS-incomplete-triples"> If however <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object
resource</a> was set to null, but there are predicates present,
then they must be stored as <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a>s,
pending the discovery of a subject that can be used as the object.
Also, <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a> should be set to a newly
created <a class="tref" title="bnode" href="#T-bnode">bnode</a>;
<div class="explanation"> Predicates for <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a>s
can be set by using one or both of the <a class="aref" href="#A-rel" title="rel">@rel</a> and <a class="aref" href="#A-rev" title="rev">@rev</a>
attributes:
<ul>
<li> If present, <a class="aref" href="#A-rel" title="rel">@rel</a> must contain one or more
IRIs, obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a> each of which is added to the <a class="tref" title="local-list-of-incomplete-triples" href="#T-local-list-of-incomplete-triples">local
list of incomplete triples</a> as follows:
<ul>
<li> If the element contains the <a class="aref" href="#A-inlist" title="inlist">@inlist</a>
attribute, then
<ul>
<li>if the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a> does not
contain a list associated with the IRI, instantiate a
new list and add to local list mappings. </li>
<li>Add:
<dl>
<dt>list</dt>
<dd>list from <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a> for
this IRI</dd>
<dt>direction</dt>
<dd>none</dd>
</dl>
</li>
</ul>
</li>
<li>Otherwise add:
<ul>
<li>
<dl>
<dt>predicate</dt>
<dd>full IRI</dd>
<dt>direction</dt>
<dd>forward</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li> If present, <a class="aref" href="#A-rev" title="rev">@rev</a> must contain one or more
IRIs, obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>, each of which is added to the <a class="tref" title="local-list-of-incomplete-triples" href="#T-local-list-of-incomplete-triples">local
list of incomplete triples</a> as follows:
<dl>
<dt>predicate</dt>
<dd>full IRI</dd>
<dt>direction</dt>
<dd>reverse</dd>
</dl>
</li>
</ul>
</div>
</li>
<li id="PS-current-object-literal"> The next step of the iteration is
to establish any <a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a>;
<div class="explanation"> Predicates for the <a class="tref" title="current-property-value" href="#T-current-property-value">current property
value</a> can be set by using <a class="aref" href="#A-property" title="property">@property</a>. If
present, one or more IRIs are obtained according to the section on
<a href="#s_curieprocessing">CURIE and IRI Processing</a>, and
then the actual literal value is obtained as follows:
<ul>
<li> as a <a class="tref" title="typed-literal" href="#T-typed-literal">typed literal</a> if <a class="aref" href="#A-datatype" title="datatype">@datatype</a>
is present, does not have an empty value according to the
section on <a href="#s_curieprocessing">CURIE and IRI
Processing</a>, and is not set to <code>XMLLiteral</code>
in the vocabulary <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>.
<p>The actual literal is either the value of <a class="aref" href="#A-content" title="content">@content</a>
(if present) <em>or</em> a string created by concatenating
the value of all descendant text nodes, of the <a class="tref" title="current-element" href="#T-current-element">current
element</a> in turn. The final string includes the
datatype IRI, as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>], which will
have been obtained according to the section on <a href="#s_curieprocessing">CURIE
and IRI Processing</a>.</p>
</li>
<li id="C7" about="#C7" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-06-17#resolution_2" rel="bibo:affirmedBy">
<em>otherwise</em>, as an <a class="tref" title="xml-literals" href="#T-xml-literals">XML
literal</a> if <a class="aref" href="#A-datatype" title="datatype">@datatype</a> is present and is
set to <code>XMLLiteral</code> in the vocabulary <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>.
<p>The value of the <a class="tref" title="xml-literals" href="#T-xml-literals">XML literal</a>
is a string created by serializing to text, all nodes that
are descendants of the <a class="tref" title="current-element" href="#T-current-element">current element</a>, i.e.,
not including the element itself, and giving it a datatype
of <code>XMLLiteral</code> in the vocabulary <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>.
The format of the resulting serialized content is as defined
in Exclusive XML Canonicalization Version [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-EXC-C14N">XML-EXC-C14N</a></cite>].</p>
<p class="note" id="C19" about="#C19" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-01-13#ISSUE__2d_60__3a__XMLLiteral_context_preservation" rel="bibo:affirmedBy">
In order to maintain maximum portability of this literal,
any children of the current node that are elements <em class="rfc2119" title="must">must</em> have
the current XML namespace declarations (if any) declared on
the serialized element. Since the child element node could
also declare new XML namespaces, the RDFa Processor <em class="rfc2119" title="must">must</em> be
careful to merge these together when generating the
serialized element definition. For avoidance of doubt, any
re-declarations on the child node <em class="rfc2119" title="must">must</em> take precedence over
declarations that were active on the current node. </p>
</li>
<li id="GK6" about="#GK6" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
<em>otherwise</em>, as an <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a> using
the value of <a class="aref" href="#A-content" title="content">@content</a> if <a class="aref" href="#A-content" title="content">@content</a> is
present.</li>
<li id="GK7" about="#GK7" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
<em>otherwise</em>, as an <a class="tref" title="iri-reference" href="#T-iri-reference">IRI Reference</a>,
obtained via the <a href="#s_curieprocessing">CURIE and IRI
Processing</a> of the first value of the <a class="aref" href="#A-resource" title="resource">@resource</a>,
<a class="aref" href="#A-href" title="href">@href</a>, or <a class="aref" href="#A-src" title="src">@src</a>, if present, <em>and</em>
the <a class="aref" href="#A-rel" title="rel">@rel</a>, <a class="aref" href="#A-rev" title="rev">@rev</a>, or <a class="aref" href="#A-content" title="content">@content</a>
attributes are <em>not</em> present.</li>
<li id="GK8" about="#GK8" resource="http://www.w3.org/2010/02/rdfa/meetings/2011-11-10#resolution_2" rel="bibo:affirmedBy">
<em>otherwise</em>, if <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is present and <a class="aref" href="#A-about" title="about">@about</a>
is not, the value of <a class="tref" title="typed-resource" href="#T-typed-resource">typed resource</a>. </li>
<li id="C8" about="#C8" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-05-13#resolution_2" rel="bibo:affirmedBy">
<em>otherwise</em> as a <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a>.
<p>Additionally, if there is a value for <dfn title="current-language" id="T-current-language">current
language</dfn> then the value of the <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a>
should include this language information, as described in
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]. The actual literal is either the value of
<a class="aref" href="#A-content" title="content">@content</a> (if present) <em>or</em> a string
created by concatenating the text content of each of the
descendant elements of the <a class="tref" title="current-element" href="#T-current-element">current element</a> in
document order.</p>
</li>
</ul>
<p>The <a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a> is then used with each
predicate as follows:</p>
<ul>
<li>If the element also includes the <a class="aref" href="#A-inlist" title="inlist">@inlist</a>
attribute, the <a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a> is added
to the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a> as follows:
<ul>
<li>if the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a> does not contain
a list associated with the predicate IRI, instantiate a
new list and add to local list mappings</li>
<li>add the <a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a> to the list
associated with the predicate IRI in the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list
mapping</a></li>
</ul>
</li>
<li>Otherwise the <a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a> is used
to generate a triple as follows:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="new-subject" href="#T-new-subject">new subject</a></dd>
<dt>predicate</dt>
<dd>full IRI</dd>
<dt>object</dt>
<dd><a class="tref" title="current-property-value" href="#T-current-property-value">current property value</a></dd>
</dl>
</li>
</ul>
</div>
<!-- <p>Once the triple has been created, if the <tdef>datatype</tdef> of the <tref>current property value</tref> is <code>rdf:XMLLiteral</code>,
then the <tref>recurse</tref> flag is set to <code>false</code>.</p> -->
</li>
<li id="PS-complete-triples"> If the <a class="tref" title="skip-element" href="#T-skip-element">skip element</a> flag
is 'false', <em>and</em> <a class="tref" title="new-subject" href="#T-new-subject">new subject</a> was set to a
non-null value, then any <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a>s <em>within
the current context</em> should be completed:
<div class="explanation"> The <a class="tref" title="list-of-incomplete-triples" href="#T-list-of-incomplete-triples">list of incomplete triples</a>
from the current <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a> (<em>not</em>
the <a class="tref" title="local-list-of-incomplete-triples" href="#T-local-list-of-incomplete-triples">local list of incomplete triples</a>) will contain
zero or more predicate IRIs. This list is iterated and is and each
of the predicates is used with <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> and <a class="tref" title="new-subject" href="#T-new-subject">new
subject</a> to generate a triple or add a new element to the
<a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a>. Note that at each level there are
<em>two</em> lists of <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a>s; one for
the current processing level (which is passed to each child
element in the previous step), and one that was received as part
of the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>. It is the latter that is
used in processing during this step. </div>
<div class="explanation"> Note that each <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a>
has a <dfn title="direction" id="T-direction">direction</dfn> value that it used to determine what
will become the subject, and what will become the object, of each
generated triple:
<ul>
<li>If <a class="tref" title="direction" href="#T-direction">direction</a> is 'none', the <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>
is added to the list from the iterated <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete
triple</a>. </li>
<li> If <a class="tref" title="direction" href="#T-direction">direction</a> is 'forward' then the following
triple is generated:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a></dd>
<dt>predicate</dt>
<dd>the predicate from the iterated <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a></dd>
<dt>object</dt>
<dd><a class="tref" title="new-subject" href="#T-new-subject">new subject</a></dd>
</dl>
</li>
<li> If <a class="tref" title="direction" href="#T-direction">direction</a> is neither 'forward' nor 'none'
then this is the triple generated:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="new-subject" href="#T-new-subject">new subject</a></dd>
<dt>predicate</dt>
<dd>the predicate from the iterated <a class="tref" title="incomplete-triple" href="#T-incomplete-triple">incomplete triple</a></dd>
<dt>object</dt>
<dd><a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a></dd>
</dl>
</li>
</ul>
</div>
</li>
<li id="PS-recurse"> Next, all elements that are children of the <a class="tref" title="current-element" href="#T-current-element">current
element</a> are processed using the rules described here, using
a new <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>, initialized as follows:
<ul>
<li> If the <a class="tref" title="skip-element" href="#T-skip-element">skip element</a> flag is 'true' then the new
<a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a> is a copy of the current context
that was passed in to this level of processing, with the <a class="tref" title="language" href="#T-language">language</a>
and <a class="tref" title="list-of-iri-mappings" href="#T-list-of-iri-mappings">list of IRI mappings</a> values replaced with the
local values; </li>
<li> Otherwise, the values are:
<ul>
<li>the <a class="tref" title="base" href="#T-base">base</a> is set to the <a class="tref" title="base" href="#T-base">base</a>
value of the current <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>;</li>
<li>the <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> is set to the value of <a class="tref" title="new-subject" href="#T-new-subject">new
subject</a>, if non-null, <em>or</em> the value of the
<a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> of the current <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a>;</li>
<li>the <a class="tref" title="parent-object" href="#T-parent-object">parent object</a> is set to value of <a class="tref" title="current-object-resource" href="#T-current-object-resource">current
object resource</a>, if non-null, <em>or</em> the
value of <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>, if non-null, <em>or</em>
the value of the <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a> of the current
<a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a>;</li>
<li>the <a class="tref" title="list-of-iri-mappings" href="#T-list-of-iri-mappings">list of IRI mappings</a> is set to the <a class="tref" title="local-list-of-iri-mappings" href="#T-local-list-of-iri-mappings">local
list of IRI mappings</a>;</li>
<li>the <a class="tref" title="list-of-incomplete-triples" href="#T-list-of-incomplete-triples">list of incomplete triples</a> is set to the
<a class="tref" title="local-list-of-incomplete-triples" href="#T-local-list-of-incomplete-triples">local list of incomplete triples</a>;</li>
<li>the <a class="tref" title="list-mapping" href="#T-list-mapping">list mapping</a> is set to the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local
list mapping</a>;</li>
<li><a class="tref" title="language" href="#T-language">language</a> is set to the value of <a class="tref" title="current-language" href="#T-current-language">current
language</a>.</li>
<!-- <li>the <tref>term mappings</tref> is set to the value of the
<tref>local term mappings</tref>.</li> -->
<li>the <a class="tref" title="default-vocabulary" href="#T-default-vocabulary">default vocabulary</a> is set to the value
of the <a class="tref" title="local-default-vocabulary" href="#T-local-default-vocabulary">local default vocabulary</a>.</li>
</ul>
</li>
</ul>
</li>
<li id="PS-Lists"> Once all the child elements have been traversed,
list triples are generated, if necessary.
<div class="explanation"> For each IRI in the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list
mapping</a>, if the equivalent list does not exist in the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a>, indicating that the list was originally defined
on the current element, use the list as follows:
<ul>
<li>Create a new ‘bnode’ array containing newly created <a class="tref" title="bnode" href="#T-bnode">bnode</a>s,
one for each element in the list</li>
<li>For each pair of <a class="tref" title="bnode" href="#T-bnode">bnode</a> and IRI from the list
the following triple is generated:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="bnode" href="#T-bnode">bnode</a></dd>
<dt>predicate</dt>
<dd>http://www.w3.org/1999/02/22-rdf-syntax-ns#first</dd>
<dt>object</dt>
<dd>full IRI</dd>
</dl>
</li>
<li>For each element in the ‘bnode’ array the following triple
is generated:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="bnode" href="#T-bnode">bnode</a></dd>
<dt>predicate</dt>
<dd>http://www.w3.org/1999/02/22-rdf-syntax-ns#rest</dd>
<dt>object</dt>
<dd>next element in the ‘bnode’ array or, if that does not
exist, http://www.w3.org/1999/02/22-rdf-syntax-ns#nil</dd>
</dl>
</li>
<li>A single additional triple is generated:
<dl>
<dt>subject</dt>
<dd><a class="tref" title="current-subject" href="#T-current-subject">current subject</a></dd>
<dt>predicate</dt>
<dd>full IRI of the <a class="tref" title="local-list-mapping" href="#T-local-list-mapping">local list mapping</a>
associated with this list</dd>
<dt>object</dt>
<dd>first element of the ‘bnode’ array</dd>
</dl>
</li>
</ul>
</div>
</li>
</ol>
</div>
<div id="processor-status" typeof="bibo:Chapter" about="#processor-status" class="section">
<h3><span class="secno">7.6 </span>Processor Status</h3>
<p> The processing rules covered in the previous section are designed to
extract as many triples as possible from a document. The RDFa
Processor is designed to continue processing, even in the event of
errors. For example, failing to resolve a prefix mapping or <a class="tref" title="term" href="#T-term">term</a>
would result in the RDFa Processor skipping the generation of a triple
and continuing with document processing. There are cases where knowing
each RDFa Processor warning or error would be beneficial to authors.
The <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a> is designed as a possible mechanism
to capture all informational, warning, and error messages as triples
from the RDFa Processor. These status triples may be retrieved and
used to aid RDFa authoring or automated error detection. </p>
<p id="C15" about="#C15" rel="bibo:affirmedBy" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-15#resolution_1">
If an RDFa Processor supports the generation of a processor graph,
then it <em class="rfc2119" title="must">must</em> generate a set of triples when the following processing
issues occur: </p>
<ul>
<li>An rdfa:Error <em class="rfc2119" title="must">must</em> be generated when the document fails to be
fully processed as a result of non-conformant host language markup.</li>
<li>A rdfa:Warning <em class="rfc2119" title="must">must</em> be generated when a CURIE prefix fails to be
resolved.</li>
<li>A rdfa:Warning <em class="rfc2119" title="must">must</em> be generated when a Term fails to be resolved.</li>
</ul>
<p> Other implementation-specific rdfa:Info, rdfa:Warning, or rdfa:Error
triples <em class="rfc2119" title="may">may</em> be generated by the RDFa Processor. </p>
<div id="accessing-the-processor-graph" typeof="bibo:Chapter" about="#accessing-the-processor-graph" class="section">
<h4><span class="secno">7.6.1 </span>Accessing the Processor Graph</h4>
<p> Accessing the <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a> may be accomplished in
a variety of ways and is dependent on the type of RDFa Processor and
access method that the developer is utilizing. </p>
<p> SAX-based processors or processors that utilize function or method
callbacks to report the generation of triples are classified as <dfn title="event-based-rdfa-processor" id="T-event-based-rdfa-processor">event-based
RDFa Processor</dfn>s. For Event-based RDFa Processors, the
software <em class="rfc2119" title="must">must</em> allow the developer to register a function or callback
that is called when a triple is generated for the <a class="tref" title="processor-graph" href="#T-processor-graph">processor
graph</a>. The callback <em class="rfc2119" title="may">may</em> be the same as the one that is used
for the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> as long as it can be determined
if a generated triple belongs in the <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a>
or the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>. </p>
<p> A <dfn title="whole-graph-rdfa-processor" id="T-whole-graph-rdfa-processor">whole-graph RDFa Processor</dfn> is defined as any RDFa
Processor that processes the entire document and only allows
developer access to the triples after processing has completed. RDFa
Processors that typically fall into this category express their
output via a single call using RDF/XML, N3, TURTLE, or N-Triples
notation. For whole-graph RDFa Processors, the software <em class="rfc2119" title="must">must</em> allow
the developer to specify if they would like to retrieve the <a class="tref" title="output-graph" href="#T-output-graph">output
graph</a>, the <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a>, or both graphs as
a single, combined graph from the RDFa Processor. <span id="whole-graph-output-graph-preference" about="#whole-graph-output-graph-preference" rel="bibo:affirmedBy" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-01#resolution_1">
If the graph preference is not specified, the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>
<em class="rfc2119" title="must">must</em> be returned. </span> </p>
<p> An <dfn title="web-service-rdfa-processor" id="T-web-service-rdfa-processor">web service RDFa Processor</dfn> is defined as any RDFa
Processor that is capable of processing a document by performing an
HTTP GET, POST or similar action on an RDFa Processor IRI. For this
class of RDFa Processor, the software <em class="rfc2119" title="must">must</em> allow the caller to
specify if they would like to retrieve the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>,
the <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a>, or both graphs as a single,
combined graph from the web service. The <code>rdfagraph</code>
query parameter <em class="rfc2119" title="must">must</em> be used to specify the value. The allowable
values are <code>output</code>, <code>processor</code> or both
values, in any order, separated by a comma character. <span id="web-service-output-graph-preference" about="#web-service-output-graph-preference" rel="bibo:affirmedBy" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-07-01#resolution_1">
If the graph preference is not specified, the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>
<em class="rfc2119" title="must">must</em> be returned. </span> </p>
</div>
<div id="processor-graph-terms" typeof="bibo:Chapter" about="#processor-graph-terms" class="section">
<h4><span class="secno">7.6.2 </span>Processor Graph Terms</h4>
<p> To ensure interoperability, a core hierarchy of classes is defined
for the content of the processor graph. Separate errors or warnings
are resources (typically blank nodes) of a specific type, with
additional properties giving more details on the error condition or
the warning. This specification defines only the top level classes
and the ones referring to the error and warning conditions defined <a href="#processor-status">explicitly</a>
by this document. Other, implementation-specific subclasses may be
defined by the RDFa Processor.</p>
<p>The top level classes are <code>rdfa:Error</code>, <code>rdfa:Warning</code>,
and <code>rdfa:Info</code>, defined as part of the <a href="#processor-graph-reporting">RDFa
Vocabulary</a>. Furthermore, a single property is defined on those
classes, namely <code>rdfa:context</code>, that provides an extra
context for the error, e.g., http response, an XPath information, or
simply the IRI to the RDFa resource. Usage of this property is
optional, and more than one triple can be used with this predicate
on the same subject. Finally, error and warning instances <em class="rfc2119" title="should">should</em> use
the <code>dc:description</code> and <code>dc:date</code>
properties. <code>dc:description</code> should provide a short,
human readable but implementation dependent description of the
error. <code>dc:date</code> should give the time when the error was
found and it is advised to be as precise as possible to allow the
detection of, for example, possible network errors. </p>
<p>The example below shows the triples that should be minimally
present in the processor graph as a result of an error (the content
of the literal for the <code>dc:description</code> predicate is
implementation dependent): </p>
<pre class="example">@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
@prefix xsd: &lt;http://www.w3.org/2001/XMLSchema#&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
[] a rdfa:DocumentError ;
dc:description &quot;The document could not be parsed due to parsing errors&quot; ;
dc:date &quot;2010-06-30T13:40:23&quot;^^xsd:dateTime .</pre>
<p>A slightly more elaborate example makes use of the <code>rdfa:context</code>
property to provide further information, using external vocabularies
to represent HTTP headers or XPointer information (note that a
processor may not have these information in all cases, i.e., these <code>rdfa:context</code>
information are not required):</p>
<pre class="example">@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
@prefix xsd: &lt;http://www.w3.org/2001/XMLSchema#&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix ptr: &lt;http://www.w3.org/2009/pointers#&gt; .
@prefix http: &lt;http://www.w3.org/2006/http#&gt; .
[] a rdfa:DocumentError ;
dc:description &quot;The document could not be parsed due to parsing errors&quot; ;
dc:date &quot;2010-06-30T13:40:23&quot;^^xsd:dateTime ;
rdfa:context &lt;http://www.example.org/doc&gt; ;
rdfa:context [
a ptr:Pointer ;
# detailed xpointer/xpath information provided here to locate the
# error
] ;
rdfa:context [
a http:Response ;
http:responseCode &lt;http://www.w3.org/2006/http#404&gt;
# Get the HTTP response headers on the request for the source file.
].</pre> </div>
</div>
<div id="vocabulary-expansion" typeof="bibo:Chapter" about="#vocabulary-expansion" class="section">
<h3><span class="secno">7.7 </span>Vocabulary Expansion</h3>
<p> Processors <em class="rfc2119" title="may">may</em> perform limited RDFS entailment rules to perform
vocabulary expansion, as described in <a href="#s_vocab_expansion">RDFa
Vocabulary Expansion</a>. </p>
</div>
</div>
<div class="informative section" id="s_rdfaindetail" typeof="bibo:Chapter" about="#s_rdfaindetail">
<!-- OddPage -->
<h2><span class="secno">8. </span>RDFa Processing in detail</h2><p><em>This section is non-normative.</em></p>
<p> This section provides an in-depth examination of the processing steps
described in the previous section. It also includes examples which may
help clarify some of the steps involved. </p>
<p> The key to processing is that a triple is generated whenever a
predicate/object combination is detected. The actual triple generated
will include a subject that may have been set previously, so this is
tracked in the current <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation context</a> and is called
the <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a>. Since the subject will default to the
current document if it hasn't been set explicitly, then a
predicate/object combination is always enough to generate one or more
triples. </p>
<p> The attributes for setting a predicate are <a class="aref" href="#A-rel" title="rel">@rel</a>, <a class="aref" href="#A-rev" title="rev">@rev</a>
and <a class="aref" href="#A-property" title="property">@property</a>, whilst the attributes for setting an object
are <a class="aref" href="#A-resource" title="resource">@resource</a>, <a class="aref" href="#A-href" title="href">@href</a>, <a class="aref" href="#A-content" title="content">@content</a>,
and <a class="aref" href="#A-src" title="src">@src</a>. <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is unique in that it sets <em>both</em>
a predicate and an object at the same time (and also a subject when it
appears in the absence of other attributes that would set a subject).
Inline content might also set an object, if <a class="aref" href="#A-content" title="content">@content</a> is not
present, but <a class="aref" href="#A-property" title="property">@property</a> is present. </p>
<p class="note"> There are many examples in this section. The examples are
all written using XHTML+RDFa. However, the explanations are relevant
regardless of the Host Language.</p>
<div id="changing-the-evaluation-context" typeof="bibo:Chapter" about="#changing-the-evaluation-context" class="section">
<h3><span class="secno">8.1 </span>Changing the evaluation context</h3>
<div id="setting-the-current-subject" typeof="bibo:Chapter" about="#setting-the-current-subject" class="section">
<h4><span class="secno">8.1.1 </span>Setting the current subject</h4>
<p>When triples are created they will always be in relation to a
subject resource which is provided either by <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>
(if there are rules on the current element that have set a subject)
or <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a>, as passed in via the <a class="tref" title="evaluation-context" href="#T-evaluation-context">evaluation
context</a>. This section looks at the specific ways in which
these values are set. Note that it doesn't matter how the subject is
set, so in this section we use the idea of the <dfn title="current-subject" id="T-current-subject">current
subject</dfn> which may be <em>either</em> <a class="tref" title="new-subject" href="#T-new-subject">new subject</a>
or <a class="tref" title="parent-subject" href="#T-parent-subject">parent subject</a>.</p>
<div id="the-current-document" typeof="bibo:Chapter" about="#the-current-document" class="section">
<h5><span class="secno">8.1.1.1 </span>The current document</h5>
<p>When parsing begins, the <a class="tref" title="current-subject" href="#T-current-subject">current subject</a> will be
the IRI of the document being parsed, or a value as set by a Host
Language-provided mechanism (e.g., the <code>base</code> element
in (X)HTML). This means that by default any metadata found in the
document will concern the document itself:</p>
<pre class="example">&lt;html&gt;
&lt;head&gt;
&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;
<span class="hilite">&lt;link rel=&quot;foaf:primaryTopic&quot; href=&quot;#bbq&quot; /&gt;</span>
<span class="hilite">&lt;meta property=&quot;dc:creator&quot; content=&quot;Jo&quot; /&gt;</span>
&lt;/head&gt;
&lt;body&gt;
...
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>This would generate the following triples:</p>
<pre class="example">&lt;&gt; foaf:primaryTopic &lt;#bbq&gt; .
&lt;&gt; dc:creator &quot;Jo&quot; .</pre>
<p>It is possible for the data to appear elsewhere in the document:</p>
<pre class="example">&lt;html&gt;
&lt;head&gt;
&lt;title&gt;Jo's Blog&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;h1&gt;<span class="hilite">&lt;span property=&quot;dc:creator&quot;&gt;Jo&lt;/span&gt;</span>'s blog&lt;/h1&gt;
&lt;p&gt;
Welcome to my blog.
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>which would still generate the triple:</p>
<pre class="example">&lt;&gt; dc:creator &quot;Jo&quot; .</pre>
<p>In (X)HTML the value of <code>base</code> may change the initial
value of <a class="tref" title="current-subject" href="#T-current-subject">current subject</a>:</p>
<pre class="example">&lt;html&gt;
&lt;head&gt;
<span class="hilite">&lt;base href=&quot;http://www.example.org/jo/blog&quot; /&gt;</span>
&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;
&lt;link rel=&quot;foaf:primaryTopic&quot; href=&quot;#bbq&quot; /&gt;
&lt;meta property=&quot;dc:creator&quot; content=&quot;Jo&quot; /&gt;
&lt;/head&gt;
&lt;body&gt;
...
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>An RDFa Processor should now generate the following triples,
regardless of the IRI from which the document is served:</p>
<pre class="example">&lt;http://www.example.org/jo/blog&gt; foaf:primaryTopic &lt;#bbq&gt; .
&lt;http://www.example.org/jo/blog&gt; dc:creator &quot;Jo&quot; .</pre> </div>
<div id="using--about" typeof="bibo:Chapter" about="#using--about" class="section">
<h5><span class="secno">8.1.1.2 </span>Using <a class="aref" href="#A-about" title="about">@about</a></h5>
<p>As processing progresses, any <a class="aref" href="#A-about" title="about">@about</a> attributes will
change the <a class="tref" title="current-subject" href="#T-current-subject">current subject</a>. The value of <a class="aref" href="#A-about" title="about">@about</a>
is an IRI or a CURIE. If it is a relative IRI then it needs to be
resolved against the current <a class="tref" title="base" href="#T-base">base</a> value. To
illustrate how this affects the statements, note in this markup
how the properties inside the (X)HTML <code>body</code> element
become part of a new calendar event object, rather than referring
to the document as they do in the head of the document: </p>
<pre class="example">&lt;html prefix=&quot;cal: http://www.w3.org/2002/12/cal/ical#&quot;&gt;
&lt;head&gt;
&lt;title&gt;Jo's Friends and Family Blog&lt;/title&gt;
&lt;link rel=&quot;foaf:primaryTopic&quot; href=&quot;#bbq&quot; /&gt;
&lt;meta property=&quot;dc:creator&quot; content=&quot;Jo&quot; /&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;p <span class="hilite">about=&quot;#bbq&quot;</span> <span class="hilite">typeof=&quot;cal:Vevent&quot;</span>&gt;
I'm holding
&lt;span <span class="hilite">property=&quot;cal:summary&quot;</span>&gt;
one last summer barbecue
&lt;/span&gt;,
on
&lt;span <span class="hilite">property=&quot;cal:dtstart&quot;</span> content=&quot;2015-09-16T16:00:00-05:00&quot;
datatype=&quot;xsd:dateTime&quot;&gt;
September 16th at 4pm
&lt;/span&gt;.
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>With this markup an RDFa Processor will generate the following
triples:</p>
<pre class="example">&lt;&gt; foaf:primaryTopic &lt;#bbq&gt; .
&lt;&gt; dc:creator &quot;Jo&quot; .
<span class="hilite">&lt;#bbq&gt; rdf:type cal:Vevent .</span>
<span class="hilite">&lt;#bbq&gt; cal:summary &quot;one last summer barbecue&quot; .</span>
<span class="hilite">&lt;#bbq&gt; cal:dtstart &quot;2015-09-16T16:00:00-05:00&quot;^^xsd:dateTime .</span></pre>
<p>Other kinds of resources can be used to set the <a class="tref" title="current-subject" href="#T-current-subject">current
subject</a>, not just references to web-pages. Although not
advised, email addresses might be used to represent a person:</p>
<pre class="example">John knows
&lt;a <span class="hilite">about=&quot;mailto:john@example.org&quot;</span>
rel=&quot;foaf:knows&quot; href=&quot;mailto:sue@example.org&quot;&gt;Sue&lt;/a&gt;.
Sue knows
&lt;a <span class="hilite">about=&quot;mailto:sue@example.org&quot;</span>
rel=&quot;foaf:knows&quot; href=&quot;mailto:jim@example.org&quot;&gt;Jim&lt;/a&gt;.</pre>
<p>This should generate the following triples:</p>
<pre class="example">&lt;mailto:john@example.org&gt; foaf:knows &lt;mailto:sue@example.org&gt; .
&lt;mailto:sue@example.org&gt; foaf:knows &lt;mailto:jim@example.org&gt; .</pre>
<p>Similarly, authors may make statements about images:</p>
<pre class="example">&lt;div <span class="hilite">about=&quot;photo1.jpg&quot;</span>&gt;
this photo was taken by
&lt;span property=&quot;dc:creator&quot;&gt;Mark Birbeck&lt;/span&gt;
&lt;/div&gt;</pre>
<p>which should generate the following triples:</p>
<pre class="example">&lt;photo1.jpg&gt; dc:creator &quot;Mark Birbeck&quot; .</pre> </div>
<div id="typing-resources-with--typeof" typeof="bibo:Chapter" about="#typing-resources-with--typeof" class="section">
<h5><span class="secno">8.1.1.3 </span>Typing resources with <a class="aref" href="#A-typeof" title="typeof">@typeof</a></h5>
<p><a class="aref" href="#A-typeof" title="typeof">@typeof</a> defines typing triples. <a class="aref" href="#A-typeof" title="typeof">@typeof</a>
works differently to other ways of setting a predicate since the
predicate is always <code>rdf:type</code>, which means that the
processor only requires one attribute, the value of the type. The
question is: which resource gets these typing information?</p>
<p>If the element has an <a class="aref" href="#A-about" title="about">@about</a>, which creates a new
context for statements, the typing relationships are defined on
that resource. For example, the following:</p>
<pre class="example">&lt;div <span class="hilite"> about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot; typeof=&quot;foaf:Person&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;foaf:givenName&quot;&gt;Albert&lt;/span&gt;
&lt;/div&gt;</pre>
<p>also creates the triple:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt; rdf:type foaf:Person .</pre>
<p>The <a class="aref" href="#A-about" title="about">@about</a> attribute is the main source for typing;
if it is present on an element, it determines the effect of <a class="aref" href="#A-typeof" title="typeof">@typeof</a>
with the highest priority. If <a class="aref" href="#A-about" title="about">@about</a> is <em>not</em>
present, but the element is used only to define possible subject
resources via, e.g., <a class="aref" href="#A-resource" title="resource">@resource</a> (i.e., there is <em>no</em>
<a class="aref" href="#A-rel" title="rel">@rel</a>, <a class="aref" href="#A-rev" title="rev">@rev</a>, or <a class="aref" href="#A-property" title="property">@property</a>
present), then that resource is used for the typed resource, just
like <a class="aref" href="#A-about" title="about">@about</a>.</p>
<p>If an <a class="aref" href="#A-rel" title="rel">@rel</a> is present (and still no <a class="aref" href="#A-about" title="about">@about</a>)
then the explicit object of the triples defined by <a class="aref" href="#A-rel" title="rel">@rel</a>
is typed. For example, in the case of:</p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;div rel=&quot;dbp:birthPlace&quot;
<span class="hilite">resource=&quot;http://dbpedia.org/resource/German_Empire&quot;</span>
<span class="hilite">typeof=&quot;http://schema.org/Country&quot;</span>&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>the generated triples also include:</p>
<pre class="example">&lt;http://dbpedia.org/resource/German_Empire&gt; rdf:type &lt;http://schema.org/Country&gt; .</pre>
<p>Finally, <a class="aref" href="#A-typeof" title="typeof">@typeof</a> also has the additional feature of
creating a new context for statements, <em>in case no other
attributes define any</em>. This involves generating a new <a class="tref" title="bnode" href="#T-bnode">bnode</a>
(see below for more about bnodes). For example, an author may wish
to create markup for a person using the FOAF vocabulary, but
without having a clear identifier for the item: </p>
<pre class="example">&lt;div <span class="hilite">typeof=&quot;foaf:Person&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;foaf:givenName&quot;&gt;Albert&lt;/span&gt;
&lt;/div&gt;</pre>
<p> This markup would cause a <a class="tref" title="bnode" href="#T-bnode">bnode</a> to be created
which has a 'type' of <code>foaf:Person</code>, as well as name
and given name properties: </p>
<pre class="example">_:a rdf:type foaf:Person .
_:a foaf:name &quot;Albert Einstein&quot; .
_:a foaf:givenName &quot;Albert&quot; .</pre>
<p>This usage of <a class="aref" href="#A-typeof" title="typeof">@typeof</a> is a shorthand for: </p>
<pre class="example">&lt;div <span class="hilite">about=&quot;_:a&quot; typeof=&quot;foaf:Person&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;foaf:givenName&quot;&gt;Albert&lt;/span&gt;
&lt;/div&gt;</pre>
<p>Similarly, </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; <span class="hilite">typeof=&quot;http://schema.org/Country&quot;</span>&gt;
&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>generates:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&quot;&gt; dbp:birthPlace _:b .
_:b dbp:conventionalLongName &quot;the German Empire&quot; .</pre>
<div class="explanation"> A <a class="tref" title="bnode" href="#T-bnode">bnode</a> is simply a unique
identifier that is only available to the processor, not to any
external software. By generating values internally, the processor
is able to keep track of properties for <code>_:a</code> as being
distinct from <code>_:b</code>. But by not exposing these values
to any external software, it is possible to have complete control
over the identifier, as well as preventing further statements
being made about the item. </div>
<div id="chaining-with--property-and--typeof" typeof="bibo:Chapter" about="#chaining-with--property-and--typeof" class="section">
<h6><span class="secno">8.1.1.3.1 </span>Chaining with <a class="aref" href="#A-property" title="property">@property</a> and <a class="aref" href="#A-typeof" title="typeof">@typeof</a></h6>
<p>As emphasized in the <a href="#s_chaining">section on chaining</a>,
one of the main differences between <a class="aref" href="#A-property" title="property">@property</a> and <a class="aref" href="#A-rel" title="rel">@rel</a>
(or <a class="aref" href="#A-rev" title="rev">@rev</a>) is that the former does not induce
chaining. The <em>only</em> exception to this rule is when <a class="aref" href="#A-typeof" title="typeof">@typeof</a>
is also present on the element. In that case the effect of <a class="aref" href="#A-property" title="property">@property</a>
is identical to <a class="aref" href="#A-rel" title="rel">@rel</a>. For example, the previous
example could have been written as: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;div property=&quot;dbp:birthPlace&quot; <span class="hilite">typeof=&quot;http://schema.org/Country&quot;</span>&gt;
&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>generating the same triples as before.</p>
</div>
</div>
<div id="determining-the-subject-with-neither--about-nor--typeof" typeof="bibo:Chapter" about="#determining-the-subject-with-neither--about-nor--typeof" class="section">
<h5><span class="secno">8.1.1.4 </span>Determining the subject with neither <a class="aref" href="#A-about" title="about">@about</a> nor <a class="aref" href="#A-typeof" title="typeof">@typeof</a></h5>
<p> As described in the previous two sections, <a class="aref" href="#A-about" title="about">@about</a>
will always take precedence and mark a new subject, but if no <a class="aref" href="#A-about" title="about">@about</a>
value is available then <a class="aref" href="#A-typeof" title="typeof">@typeof</a> will do the same job,
although using an implied identifier, i.e., a <a class="tref" title="bnode" href="#T-bnode">bnode</a>.</p>
<p> But if neither <a class="aref" href="#A-about" title="about">@about</a> or <a class="aref" href="#A-typeof" title="typeof">@typeof</a> are
present, there are a number of ways that the subject could be
arrived at. One of these is to 'inherit' the subject from the
containing statement, with the value to be inherited set either
explicitly, or implicitly. </p>
<div id="inheriting-subject-from--resource" typeof="bibo:Chapter" about="#inheriting-subject-from--resource" class="section">
<h6><span class="secno">8.1.1.4.1 </span>Inheriting subject from <a class="aref" href="#A-resource" title="resource">@resource</a></h6>
<p> The most usual way that an inherited subject might get set
would be when the parent statement has an object that is a
resource. Returning to the earlier example, in which the long
name for the German_Empire was added, the following markup was
used: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; resource=&quot;http://dbpedia.org/resource/German_Empire&quot; /&gt;
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;
property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;</span>
&lt;/div&gt;</pre>
<p> In an earlier illustration the subject and object for the
German Empire were connected by removing the <a class="aref" href="#A-resource" title="resource">@resource</a>,
relying on the <a class="aref" href="#A-about" title="about">@about</a> to set the object: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
<span class="hilite">&lt;div rel=&quot;dbp:birthPlace&quot;&gt;</span>
&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;
property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> but it is also possible for authors to achieve the same effect
by removing the <a class="aref" href="#A-about" title="about">@about</a> and leaving the <a class="aref" href="#A-resource" title="resource">@resource</a>:
</p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; <span class="hilite">resource=&quot;http://dbpedia.org/resource/German_Empire&quot;</span>&gt;
&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> In this situation, all statements that are 'contained' by the
object resource representing the German Empire (the value in <a class="aref" href="#A-resource" title="resource">@resource</a>)
will have the same subject, making it easy for authors to add
additional statements: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; resource=&quot;http://dbpedia.org/resource/German_Empire&quot;&gt;
&lt;span property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
<span class="hilite">&lt;span rel=&quot;dbp-owl:capital&quot; resource=&quot;http://dbpedia.org/resource/Berlin&quot; /&gt;</span>
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>Looking at the triples that an RDFa Processor would generate,
we can see that we actually have two groups of statements; the
first group are set to refer to the <a class="aref" href="#A-about" title="about">@about</a> that
contains them:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt; foaf:name &quot;Albert Einstein&quot; .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt; dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt; dbp:birthPlace &lt;http://dbpedia.org/resource/German_Empire&gt; .</pre>
<p>whilst the second group refer to the <a class="aref" href="#A-resource" title="resource">@resource</a>
that contains them:</p>
<pre class="example">&lt;http://dbpedia.org/resource/German_Empire&gt;
dbp:conventionalLongName &quot;the German Empire&quot; .
&lt;http://dbpedia.org/resource/German_Empire&gt;
dbp-owl:capital &lt;http://dbpedia.org/resource/Berlin&gt; .</pre>
<p> Note also that the same principle described here applies to <a class="aref" href="#A-src" title="src">@src</a>
and <a class="aref" href="#A-href" title="href">@href</a>. </p>
</div>
<div id="inheriting-an-anonymous-subject" typeof="bibo:Chapter" about="#inheriting-an-anonymous-subject" class="section">
<h6><span class="secno">8.1.1.4.2 </span>Inheriting an anonymous subject</h6>
<p> There will be occasions when the author wants to connect the
subject and object as shown above, but is not concerned to name
the resource that is common to the two statements (i.e., the
object of the first statement, which is the subject of the
second). For example, to indicate that Einstein was influenced
by Spinoza the following markup could well be used: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot; rel=&quot;dbp-owl:influenced&quot;&gt;
&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> An RDFa Processor will generate the following triples: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt;
dbp-owl:influenced &lt;http://dbpedia.org/resource/Albert_Einstein&gt; .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt; foaf:name &quot;Albert Einstein&quot; .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt; dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .</pre>
<p> However, an author could just as easily say that Spinoza
influenced <em>something by the name of Albert Einstein, that
was born on March 14th, 1879</em>: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot; rel=&quot;dbp-owl:influenced&quot;&gt;
<span class="hilite">&lt;div&gt;</span>
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
<span class="hilite">&lt;/div&gt;</span>
&lt;/div&gt;</pre>
<p> In RDF terms, the item that 'represents' Einstein is <em>anonymous</em>,
since it has no IRI to identify it. However, the item is given
an automatically generated <a class="tref" title="bnode" href="#T-bnode">bnode</a>, and it is onto
this identifier that all child statements are attached: </p>
<p> An RDFa Processor will generate the following triples: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt; dbp-owl:influenced _:a .
_:a foaf:name &quot;Albert Einstein&quot; .
_:a dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .</pre>
<p> Note that the <code>div</code> is superfluous, and an RDFa
Processor will create the intermediate object even if the
element is removed: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot; rel=&quot;dbp-owl:influenced&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;/div&gt;</pre>
<p> An alternative pattern is to <em>keep</em> the <code>div</code>
and move the <a class="aref" href="#A-rel" title="rel">@rel</a> onto it: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot;&gt;
&lt;div <span class="hilite">rel=&quot;dbp-owl:influenced&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> From the point of view of the markup, this latter layout is to
be preferred, since it draws attention to the 'hanging rel'. But
from the point of view of an RDFa Processor, all of these
permutations need to be supported. </p>
</div>
</div>
</div>
</div>
<div id="s_Completing_Incomplete_Triples" typeof="bibo:Chapter" about="#s_Completing_Incomplete_Triples" class="section">
<h3><span class="secno">8.2 </span>Completing incomplete triples'</h3>
<p> When a new subject is calculated, it is also used to complete any
incomplete triples that are pending. This situation arises when the
author wants to 'chain' a number of statements together. For example,
an author could have a statement that Albert Einstein was born in the
German Empire: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
<span class="hilite">&lt;div rel=&quot;dbp:birthPlace&quot; resource=&quot;http://dbpedia.org/resource/German_Empire&quot; /&gt;</span>
&lt;/div&gt;</pre>
<p> and then a further statement that the 'long name' for this country
is <em>the German Empire</em>: </p>
<pre class="example">&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;
property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;</pre>
<p> RDFa allows authors to insert this statement as a self-contained
unit into other contexts: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp:birthPlace&quot; resource=&quot;http://dbpedia.org/resource/German_Empire&quot; /&gt;
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;
property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;</span>
&lt;/div&gt;</pre>
<p> But it also allows authors to avoid unnecessary repetition and to
'normalize' out duplicate identifiers, in this case the one for the
German Empire: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
<span class="hilite">&lt;div rel=&quot;dbp:birthPlace&quot;&gt;</span>
&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot;
property=&quot;dbp:conventionalLongName&quot;&gt;the German Empire&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> When this happens the <a class="aref" href="#A-rel" title="rel">@rel</a> for 'birth place' is
regarded as a 'hanging rel' because it has not yet generated any
triples, but these 'incomplete triples' are completed by the <a class="aref" href="#A-about" title="about">@about</a>
that appears on the next line. The first step is therefore to store
the two parts of the triple that the RDFa Processor <em>does</em>
have, but without an object: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt; dbp:birthPlace <span class="hilite">?</span> .</pre>
<p> Then as processing continues, the RDFa Processor encounters the
subject of the statement about the long name for the German Empire,
and this is used in two ways. First it is used to complete the
'incomplete triple': </p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
dbp:birthPlace <span class="hilite">&lt;http://dbpedia.org/resource/German_Empire&gt;</span> .</pre>
<p>and second it is used to generate its own triple:</p>
<pre class="example">&lt;http://dbpedia.org/resource/German_Empire&gt;
dbp:conventionalLongName &quot;the German Empire&quot; .</pre>
<p> Note that each occurrence of <a class="aref" href="#A-about" title="about">@about</a> will complete any
incomplete triples. For example, to mark up the fact that Albert
Einstein had a residence both in the German Empire and Switzerland, an
author need only specify one <a class="aref" href="#A-rel" title="rel">@rel</a> value that is then used
with multiple <a class="aref" href="#A-about" title="about">@about</a> values: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot; rel=&quot;dbp-owl:residence&quot;&gt;
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot; /&gt;</span>
<span class="hilite">&lt;span about=&quot;http://dbpedia.org/resource/Switzerland&quot; /&gt;</span>
&lt;/div&gt;</pre>
<p> In this example there is one incomplete triple: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt; dbp-owl:residence <span class="hilite">?</span> .</pre>
<p> When the processor meets each of the <a class="aref" href="#A-about" title="about">@about</a> values,
this triple is completed, giving: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
dbp-owl:residence <span class="hilite">&lt;http://dbpedia.org/resource/German_Empire&gt;</span> .
&lt;http://dbpedia.org/resource/Albert_Einstein&gt;
dbp-owl:residence <span class="hilite">&lt;http://dbpedia.org/resource/Switzerland&gt;</span> .</pre>
<p> These examples show how <a class="aref" href="#A-about" title="about">@about</a> completes triples, but
there are other situations that can have the same effect. For example,
when <a class="aref" href="#A-typeof" title="typeof">@typeof</a> creates a new <a class="tref" title="bnode" href="#T-bnode">bnode</a> (as
described above), that will be used to complete any 'incomplete
triples'. To illustrate, to indicate that Spinoza influenced both
Einstein and Schopenhauer, the following markup could be used: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot;&gt;
&lt;div rel=&quot;dbp-owl:influenced&quot;&gt;
&lt;div <span class="hilite">typeof=&quot;foaf:Person&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;/div&gt;
&lt;div <span class="hilite">typeof=&quot;foaf:Person&quot;</span>&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Arthur Schopenhauer&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1788-02-22&lt;/span&gt;
&lt;/div&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p>First the following incomplete triple is stored:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt; dbp-owl:influenced <span class="hilite">?</span> .</pre>
<p> Then when the RDFa Processor processes the two occurrences of <a class="aref" href="#A-typeof" title="typeof">@typeof</a>,
each generates a <a class="tref" title="bnode" href="#T-bnode">bnode</a>, which is used to both complete
the 'incomplete triple', and to set the subject for further
statements: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&quot;&gt; dbp-owl:influenced <span class="hilite">_:a</span> .
<span class="hilite">_:a</span> rdf:type foaf:Person .
<span class="hilite">_:a</span> foaf:name &quot;Albert Einstein&quot; .
<span class="hilite">_:a</span> dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .
&lt;http://dbpedia.org/resource/Baruch_Spinoza&quot;&gt; dbp-owl:influenced <span class="hilite">_:b</span> .
<span class="hilite">_:b</span> rdf:type foaf:Person .
<span class="hilite">_:b</span> foaf:name &quot;Arthur Schopenhauer&quot; .
<span class="hilite">_:b</span> dbp:dateOfBirth &quot;1788-02-22&quot;^^xsd:date .</pre>
<p> Triples are also 'completed' if any one of <a class="aref" href="#A-property" title="property">@property</a>, <a class="aref" href="#A-rel" title="rel">@rel</a>
or <a class="aref" href="#A-rev" title="rev">@rev</a> are present. However, unlike the situation when <a class="aref" href="#A-about" title="about">@about</a>
or <a class="aref" href="#A-typeof" title="typeof">@typeof</a> are present, all predicates are attached to
one <a class="tref" title="bnode" href="#T-bnode">bnode</a>: </p>
<pre class="example">&lt;div about=&quot;http://dbpedia.org/resource/Baruch_Spinoza&quot; rel=&quot;dbp-owl:influenced&quot;&gt;
&lt;span property=&quot;foaf:name&quot;&gt;Albert Einstein&lt;/span&gt;
&lt;span property=&quot;dbp:dateOfBirth&quot; datatype=&quot;xsd:date&quot;&gt;1879-03-14&lt;/span&gt;
&lt;div rel=&quot;dbp-owl:residence&quot;&gt;
&lt;span about=&quot;http://dbpedia.org/resource/German_Empire&quot; /&gt;
&lt;span about=&quot;http://dbpedia.org/resource/Switzerland&quot; /&gt;
&lt;/div&gt;
&lt;/div&gt;</pre>
<p> This example has two 'hanging rels', and so two situations when
'incomplete triples' will be created. Processing would proceed as
follows; first an incomplete triple is stored: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt; dbp-owl:influenced <span class="hilite">?</span> .</pre>
<p> Next, the RDFa Processor processes the predicate values for <code>foaf:name</code>,
<code>dbp:dateOfBirth</code> and <code>dbp-owl:residence</code>, but
note that only the first needs to 'complete' the 'hanging rel'. So
processing <code>foaf:name</code> generates two triples: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt; dbp-owl:influenced <span class="hilite">_:a</span> .
<span class="hilite">_:a</span> foaf:name &quot;Albert Einstein&quot; .</pre>
<p> but processing <code>dbp:dateOfBirth</code> generates only one: </p>
<pre class="example"><span class="hilite">_:a</span> dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .</pre>
<p>Processing <code>dbp-owl:residence</code> also uses the same <a class="tref" title="bnode" href="#T-bnode">bnode</a>,
but note that it also generates its own 'incomplete triple':</p>
<pre class="example">_:a dbp-owl:residence <span class="hilite">?</span> .</pre>
<p>As before, the two occurrences of <a class="aref" href="#A-about" title="about">@about</a> complete the
'incomplete triple', once each:</p>
<pre class="example">_:a dbp-owl:residence <span class="hilite">&lt;http://dbpedia.org/resource/German_Empire&gt;</span> .
_:a dbp-owl:residence <span class="hilite">&lt;http://dbpedia.org/resource/Switzerland&gt;</span> .</pre>
<p> The entire set of triples that an RDFa Processor should generate are
as follows: </p>
<pre class="example">&lt;http://dbpedia.org/resource/Baruch_Spinoza&gt; dbp-owl:influenced <span class="hilite">_:a</span> .
<span class="hilite">_:a</span> foaf:name &quot;Albert Einstein&quot; .
<span class="hilite">_:a</span> dbp:dateOfBirth &quot;1879-03-14&quot;^^xsd:date .
<span class="hilite">_:a</span> dbp-owl:residence &lt;http://dbpedia.org/resource/German_Empire&gt; .
<span class="hilite">_:a</span> dbp-owl:residence &lt;http://dbpedia.org/resource/Switzerland&gt; .</pre> </div>
<div id="object-resolution" typeof="bibo:Chapter" about="#object-resolution" class="section">
<h3><span class="secno">8.3 </span>Object resolution</h3>
<p> Although objects have been discussed in the previous sections, as
part of the explanation of subject resolution, chaining, evaluation
contexts, and so on, this section will look at objects in more detail.
</p>
<p>There are two types of object, <a class="tref" title="iri-resource" href="#T-iri-resource">IRI resource</a>s and <a class="tref" title="literal" href="#T-literal">literal</a>s.</p>
<p> A <a class="tref" title="literal" href="#T-literal">literal</a> object can be set by using <a class="aref" href="#A-property" title="property">@property</a>
to express a <a class="tref" title="predicate" href="#T-predicate">predicate</a>, and then using either <a class="aref" href="#A-content" title="content">@content</a>,
or the inline text of the element that <a class="aref" href="#A-property" title="property">@property</a> is on. <em>Note
that the use of <a class="aref" href="#A-content" title="content">@content</a> prohibits the inclusion of
rich markup in your literal. If the inline content of an element
accurately represents the object, then documents should rely upon
that rather than duplicating that data using the <a class="aref" href="#A-content" title="content">@content</a>.</em></p>
<p>A <dfn title="iri-resource" id="T-iri-resource">IRI resource</dfn> object can be set using one of <a class="aref" href="#A-rel" title="rel">@rel</a>
or <a class="aref" href="#A-rev" title="rev">@rev</a> to express a <a class="tref" title="predicate" href="#T-predicate">predicate</a>, and then <em>either</em>
using one of <a class="aref" href="#A-href" title="href">@href</a>, <a class="aref" href="#A-resource" title="resource">@resource</a> or <a class="aref" href="#A-src" title="src">@src</a>
to provide an object resource explicitly, <em>or</em> using the
chaining techniques described above to obtain an object from a nested
subject, or from a <a class="tref" title="bnode" href="#T-bnode">bnode</a>. <em>Alternatively</em>, the <a class="aref" href="#A-property" title="property">@property</a>
can also be used to define an IRI resource, in the presence of an <a class="aref" href="#A-href" title="href">@href</a>,
<a class="aref" href="#A-resource" title="resource">@resource</a>, or <a class="aref" href="#A-src" title="src">@src</a> <em>and</em> in the
absence of <a class="aref" href="#A-rel" title="rel">@rel</a>, <a class="aref" href="#A-rev" title="rev">@rev</a>, <a class="aref" href="#A-datatype" title="datatype">@datatype</a>,
or <a class="aref" href="#A-content" title="content">@content</a>.</p>
<div id="object-resolution-for-the--property-attribute" typeof="bibo:Chapter" about="#object-resolution-for-the--property-attribute" class="section">
<h4><span class="secno">8.3.1 </span>Object resolution for the <a class="aref" href="#A-property" title="property">@property</a> attribute</h4>
<p> An <dfn title="object-literal" id="T-object-literal">object literal</dfn> will be generated when <a class="aref" href="#A-property" title="property">@property</a>
is present. <a class="aref" href="#A-property" title="property">@property</a> provides the predicate, and the
following sections describe how the actual literal to be generated
is determined. </p>
<div style="margin: 0pt auto; text-align: center;"> <object data="Literal_Resolution.svg" type="image/svg+xml" height="75%" width="75%">
<img src="Literal_Resolution.png" alt="Literal object resolution" />
</object>
<p><strong>Literal object resolution</strong></p>
</div>
<div id="plain-literals-1" typeof="bibo:Chapter" about="#plain-literals-1" class="section">
<h5><span class="secno">8.3.1.1 </span>Plain Literals</h5>
<p><a class="aref" href="#A-content" title="content">@content</a> can be used to indicate a <a class="tref" title="plain-literal" href="#T-plain-literal">plain
literal</a>, as follows:</p>
<pre class="example">&lt;meta about=&quot;http://internet-apps.blogspot.com/&quot;
property=&quot;dc:creator&quot; <span class="hilite">content=&quot;Mark Birbeck&quot;</span> /&gt;</pre>
<p>The <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a> can also be specified by using
the content of the element:</p>
<pre class="example">&lt;span about=&quot;http://internet-apps.blogspot.com/&quot;
property=&quot;dc:creator&quot;&gt;<span class="hilite">Mark Birbeck</span>&lt;/span&gt;</pre>
<p> Both of these examples give the following triple: </p>
<pre class="example">&lt;http://internet-apps.blogspot.com/&gt; dc:creator &quot;Mark Birbeck&quot; .</pre>
<p>The value of <a class="aref" href="#A-content" title="content">@content</a> is given precedence over any
element content, so the following would give exactly the same
triple as shown above:</p>
<pre class="example">&lt;span about=&quot;http://internet-apps.blogspot.com/&quot;
property=&quot;dc:creator&quot; <span class="hilite">content=&quot;Mark Birbeck&quot;</span>&gt;John Doe&lt;/span&gt;</pre>
<div id="language-tags" typeof="bibo:Chapter" about="#language-tags" class="section">
<h6><span class="secno">8.3.1.1.1 </span>Language Tags</h6>
<p>RDF allows <a class="tref" title="plain-literal" href="#T-plain-literal">plain literal</a>s to have a language tag,
as illustrated by the following example from [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-TESTCASES">RDF-TESTCASES</a></cite>]:</p>
<pre class="example">&lt;http://example.org/node&gt;
&lt;http://example.org/property&gt; &quot;chat&quot;<span class="hilite">@fr</span> .</pre>
<p>In RDFa the Host Language may provide a mechanism for setting
the language tag. In XHTML+RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>], for example,
the XML language attribute <span class="aref">@xml:lang</span>
or the attribute <span class="aref">@lang</span> is used to add
this information, whether the plain literal is designated by <a class="aref" href="#A-content" title="content">@content</a>,
or by the inline text of the element:</p>
<pre class="example">&lt;meta about=&quot;http://example.org/node&quot;
property=&quot;ex:property&quot; <span class="hilite">xml:lang=&quot;fr&quot;</span> content=&quot;chat&quot; /&gt;</pre>
<p>Note that the language value can be inherited as defined in
[<cite><a class="bibref" rel="biblioentry" href="#bib-XML10-4e">XML10-4e</a></cite>], so the following syntax will give the same triple
as above:</p>
<pre class="example">&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot;
prefix=&quot;ex: http://www.example.com/ns/&quot; <span class="hilite">xml:lang=&quot;fr&quot;</span>&gt;
&lt;head&gt;
&lt;title xml:lang=&quot;en&quot;&gt;Example&lt;/title&gt;
&lt;meta about=&quot;http://example.org/node&quot;
property=&quot;ex:property&quot; content=&quot;chat&quot; /&gt;
&lt;/head&gt;
...
&lt;/html&gt;</pre> </div>
</div>
<div id="typed-literals-1" typeof="bibo:Chapter" about="#typed-literals-1" class="section">
<h5><span class="secno">8.3.1.2 </span>Typed literals</h5>
<p>Literals can be given a data type using <a class="aref" href="#A-datatype" title="datatype">@datatype</a>.</p>
<p>This can be represented in RDFa as follows:</p>
<pre class="example">&lt;span property=&quot;cal:dtstart&quot; content=&quot;2015-09-16T16:00:00-05:00&quot;
<span class="hilite">datatype=&quot;xsd:dateTime&quot;</span>&gt;
September 16th at 4pm
&lt;/span&gt;.</pre>
<p>The triples that this markup generates include the datatype after
the literal:</p>
<pre class="example">&lt;&gt; cal:dtstart &quot;2015-09-16T16:00:00-05:00&quot;^^<span class="hilite">xsd:dateTime</span> .</pre> </div>
<div id="s-xml-literals" typeof="bibo:Chapter" about="#s-xml-literals" class="section">
<h5><span class="secno">8.3.1.3 </span><dfn title="xml-literals" id="T-xml-literals">XML Literals</dfn></h5>
<p>XML documents cannot contain XML markup in their attributes,
which means it is not possible to represent XML within <a class="aref" href="#A-content" title="content">@content</a>
(the following would cause an XML parser to generate an error):</p>
<pre class="example">&lt;head&gt;
&lt;meta property=&quot;dc:title&quot;
<span class="hilite">content=&quot;E = mc&lt;sup&gt;2&lt;/sup&gt;: The Most Urgent Problem of Our Time&quot;</span> /&gt;
&lt;/head&gt;</pre>
<p>RDFa therefore supports the use of normal markup to express XML
literals, by using <a class="aref" href="#A-datatype" title="datatype">@datatype</a>:</p>
<pre class="example">&lt;h2 property=&quot;dc:title&quot; datatype=&quot;rdf:XMLLiteral&quot;&gt;
<span class="hilite">E = mc&lt;sup&gt;2&lt;/sup&gt;: The Most Urgent Problem of Our Time</span>
&lt;/h2&gt;</pre>
<p>This would generate the following triple, with the XML preserved
in the literal:</p>
<pre class="example">&lt;&gt; dc:title &quot;E = mc&lt;sup&gt;2&lt;/sup&gt;: The Most Urgent Problem of Our Time&quot;^^rdf:XMLLiteral .</pre>
<p class="note"> This requires that an IRI mapping for the prefix <code>rdf</code>
has been defined. </p>
<p> In the examples given here the <code>sup</code> element is
actually part of the meaning of the literal, but there will be
situations where the extra markup means nothing, and can therefore
be ignored. In this situation omitting the <a class="aref" href="#A-datatype" title="datatype">@datatype</a>
attribute or specifying an empty <a class="aref" href="#A-datatype" title="datatype">@datatype</a> value can
be used create a plain literal: </p>
<pre class="example">&lt;p&gt;You searched for &lt;strong&gt;Einstein&lt;/strong&gt;:&lt;/p&gt;
&lt;p about=&quot;http://dbpedia.org/resource/Albert_Einstein&quot;&gt;
&lt;span property=&quot;foaf:name&quot; <span class="hilite">datatype=&quot;&quot;</span>&gt;Albert &lt;strong&gt;Einstein&lt;/strong&gt;&lt;/span&gt;
(b. March 14, 1879, d. April 18, 1955) was a German-born theoretical physicist.
&lt;/p&gt;</pre>
<p>Although the rendering of this page has highlighted the term the
user searched for, setting <a class="aref" href="#A-datatype" title="datatype">@datatype</a> to nothing
ensures that the data is interpreted as a plain literal, giving
the following triples:</p>
<pre class="example">&lt;http://dbpedia.org/resource/Albert_Einstein&gt; foaf:name <span class="hilite">&quot;Albert Einstein&quot;</span> .</pre>
<p class="note">The value of this <a class="tref" title="xml-literals" href="#T-xml-literals">XML
Literal</a> is the exclusive canonicalization
[<cite><a class="bibref" rel="biblioentry" href="#bib-XML-EXC-C14N">XML-EXC-C14N</a></cite>] of the RDFa element's value.</p>
</div>
</div>
<div id="iri-object-resolution" typeof="bibo:Chapter" about="#iri-object-resolution" class="section">
<h4><span class="secno">8.3.2 </span>IRI object resolution</h4>
<p> Most of the rules governing the processing of objects that are
resources are to be found in the processing descriptions given
above, since they are important for establishing the subject. This
section aims to highlight general concepts, and anything that might
have been missed. </p>
<p> One or more <dfn title="iri-object" id="T-iri-object">IRI object</dfn>s are needed when <a class="aref" href="#A-rel" title="rel">@rel</a>,
<a class="aref" href="#A-rev" title="rev">@rev</a>, or <a class="aref" href="#A-property" title="property">@property</a> is present. Each
attribute will cause triples to be generated when used with <a class="aref" href="#A-href" title="href">@href</a>,
<a class="aref" href="#A-resource" title="resource">@resource</a> or <a class="aref" href="#A-src" title="src">@src</a>, or with the subject
value of any nested statement if none of these attributes are
present. </p>
<p> <a class="aref" href="#A-rel" title="rel">@rel</a> and <a class="aref" href="#A-rev" title="rev">@rev</a> are essentially the
inverse of each other; whilst <a class="aref" href="#A-rel" title="rel">@rel</a> establishes a
relationship between the <a class="tref" title="current-subject" href="#T-current-subject">current subject</a> as subject,
and the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a> as the object, <a class="aref" href="#A-rev" title="rev">@rev</a>
does the exact opposite, and uses the <a class="tref" title="current-object-resource" href="#T-current-object-resource">current object resource</a>
as the subject, and the <a class="tref" title="current-subject" href="#T-current-subject">current subject</a> as the object.
</p>
<div id="using--resource-to-set-the-object" typeof="bibo:Chapter" about="#using--resource-to-set-the-object" class="section">
<h5><span class="secno">8.3.2.1 </span>Using <a class="aref" href="#A-resource" title="resource">@resource</a> to set the object</h5>
<p>RDFa provides the <a class="aref" href="#A-resource" title="resource">@resource</a> attribute as a way to
set the object of statements. This is particularly useful when
referring to resources that are not themselves navigable links:</p>
<pre class="example">&lt;html&gt;
&lt;head&gt;
&lt;title&gt;On Crime and Punishment&lt;/title&gt;
&lt;base href=&quot;http://www.example.com/candp.xhtml&quot; /&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;blockquote about=&quot;#q1&quot; rel=&quot;dc:source&quot; <span class="hilite">resource=&quot;urn:ISBN:0140449132&quot;</span> &gt;
&lt;p id=&quot;q1&quot;&gt;
Rodion Romanovitch! My dear friend! If you go on in this way
you will go mad, I am positive! Drink, pray, if only a few drops!
&lt;/p&gt;
&lt;/blockquote&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
<p>The <code>blockquote</code> element generates the following
triple:</p>
<pre class="example">&lt;http://www.example.com/candp.xhtml#q1&gt;
&lt;http://purl.org/dc/terms/source&gt; &lt;urn:ISBN:0140449132&gt; .</pre>
<p>Note that, in the example above, <a class="aref" href="#A-property" title="property">@property</a> could
have been used instead of <a class="aref" href="#A-rel" title="rel">@rel</a>, yielding the same
triple.</p>
</div>
<div id="using--href-or--src" typeof="bibo:Chapter" about="#using--href-or--src" class="section">
<h5><span class="secno">8.3.2.2 </span>Using <a class="aref" href="#A-href" title="href">@href</a> or <a class="aref" href="#A-src" title="src">@src</a></h5>
<p> If no <a class="aref" href="#A-resource" title="resource">@resource</a> is present, then <a class="aref" href="#A-href" title="href">@href</a>
or <a class="aref" href="#A-src" title="src">@src</a> are next in priority order for setting the
object. </p>
<p>When a predicate has been expressed using <a class="aref" href="#A-rel" title="rel">@rel</a>, the
<a class="aref" href="#A-href" title="href">@href</a> or <a class="aref" href="#A-src" title="src">@src</a> on the RDFa statement's
element is used to identify the object with a <a class="tref" title="iri-reference" href="#T-iri-reference">IRI reference</a>.
Their types are an IRI:</p>
<pre class="example">&lt;link about=&quot;mailto:john@example.org&quot;
<span class="hilite">rel=&quot;foaf:knows&quot; href=&quot;mailto:sue@example.org&quot;</span> /&gt;</pre>
<p>It's also possible to use both <a class="aref" href="#A-rel" title="rel">@rel</a> and <a class="aref" href="#A-rev" title="rev">@rev</a>
at the same time on an element. This is particularly useful when
two things stand in two different relationships with each other,
for example when a picture is taken <em>by</em> Mark, but that
picture also <em>depicts</em> him:</p>
<pre class="example">&lt;img about=&quot;http://www.blogger.com/profile/1109404&quot;
src=&quot;photo1.jpg&quot; <span class="hilite">rev=&quot;dc:creator&quot; rel=&quot;foaf:img&quot;</span>/&gt;</pre>
<p>which then yields two triples:</p>
<pre class="example">&lt;photo1.jpg&gt;
dc:creator &lt;http://www.blogger.com/profile/1109404&gt; .
&lt;http://www.blogger.com/profile/1109404&gt;
foaf:img &lt;photo1.jpg&gt; .</pre> </div>
<div id="incomplete-triples" typeof="bibo:Chapter" about="#incomplete-triples" class="section">
<h5 id="s_Incomplete_Triples"><span class="secno">8.3.2.3 </span>Incomplete triples</h5>
<p>When a triple predicate has been expressed using <a class="aref" href="#A-rel" title="rel">@rel</a>
or <a class="aref" href="#A-rev" title="rev">@rev</a>, but no <a class="aref" href="#A-href" title="href">@href</a>, <a class="aref" href="#A-src" title="src">@src</a>,
or <a class="aref" href="#A-resource" title="resource">@resource</a> exists on the same element, there is a
'hanging rel'. This causes the current subject and all possible
predicates (with an indicator of whether they are 'forwards, i.e.,
<a class="aref" href="#A-rel" title="rel">@rel</a> values, or not, i.e., <a class="aref" href="#A-rev" title="rev">@rev</a> values),
to be stored as 'incomplete triples' pending discovery of a
subject that could be used to 'complete' those triples.</p>
<p>This process is described in more detail in <a href="#s_Completing_Incomplete_Triples">Completing
'Incomplete Triples'</a>.</p>
</div>
</div>
</div>
<div id="list-generation" typeof="bibo:Chapter" about="#list-generation" class="section">
<h3><span class="secno">8.4 </span>List generation</h3>
<p>An RDF graph is a collection of triples. This also means that if the
graph contains two triples sharing the same subject and predicate:</p>
<pre class="example">&lt;http://www.example.com&gt; &lt;http://www.example.com/predicate&gt; &quot;first object&quot;, &quot;second object&quot; ;</pre>
<p>There is no way for an application to rely on the relative order of
the two triples when, for example, querying a database containing
these triples. For most of the applications and data sets this is not
a problem, but, in some cases, the order is important. A typical case
is publications: when a book or an article has several co-authors, the
order of the authors may be important. </p>
<p>RDF has a set of predefined predicates that have an agreed-upon
semantics of order. For example, the publication: “Semantic Annotation
and Retrieval, by Ben Adida, Mark Birbeck, and Ivan Herman” could be
described in RDF triples using these terms as follows:</p>
<pre class="example">@prefix bibo: &lt;http://purl.org/ontology/bibo/&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
[ a bibo:Chapter ;
dc:title &quot;Semantic Annotation and Retrieval&quot; ;
dc:creator [
rdf:first &quot;Ben Adida&quot; ;
rdf:rest [
rdf:first &quot;Mark Birbeck&quot; ;
rdf:rest [
rdf:first &quot;Ivan Herman&quot; ;
rdf:rest rdf:nil .
] .
] .
] .
...
]</pre>
<p>which conveys the notion of “order” for the three authors.
Admittingly, this is not very readable. However, Turtle has a
syntactic shorthand for these structures:</p>
<pre class="example">@prefix bibo: &lt;http://purl.org/ontology/bibo/&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
[ a bibo:Chapter ;
dc:title &quot;Semantic Annotation and Retrieval&quot; ;
dc:creator ( &quot;Ben Adida&quot; &quot;Mark Birbeck&quot; &quot;Ivan Herman&quot; ) .
...
]</pre>
<p>It would of course be possible to reproduce the same structure in
RDFa, using the RDF predicates <code>rdf:first</code>, <code>rdf:rest</code>,
as well as the special resource <code>rdf:nil</code>. However, to
make this easier, RDFa provides the <a class="aref" href="#A-inlist" title="inlist">@inlist</a>. What this
attributes signals is that the object generated on that element should
be put on a list; the list is used with the common predicate with the
common subject. Here is how the previous structure could look like in
RDFa:</p>
<pre class="example">&lt;p prefix=&quot;bibo: http://purl.org/ontology/bibo/ dc: http://purl.org/dc/terms/ typeof=&quot;bibo:Chapter&quot;&gt;
“&lt;span property=&quot;dc:title&quot;&gt;Semantic Annotation and Retrieval&lt;/span&gt;”, by
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span>&gt;Ben Adida&lt;/span&gt;,
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span>&gt;Mark Birbeck&lt;/span&gt;, and
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span>&gt;Ivan Herman&lt;/span&gt;.
&lt;/p&gt;</pre>
<p>Note that the order in the list is determined by the document order.
(The value of the <a class="aref" href="#A-inlist" title="inlist">@inlist</a> is not relevant, only its
presence is.)</p>
<p>Lists may also include URIs and not only literals. For example, two
of the three co-authors could decide to publicise their FOAF address
in the authors’ list:</p>
<pre class="example">&lt;p prefix=&quot;bibo: http://purl.org/ontology/bibo/ dc: http://purl.org/dc/terms/ typeof=&quot;bibo:Chapter&quot;&gt;
“&lt;span property=&quot;dc:title&quot;&gt;Semantic Annotation and Retrieval&lt;/span&gt;”, by
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span> <span class="hilite">resource=&quot;http://ben.adida.net/#me&quot;</span>&gt;Ben Adida&lt;/span&gt;,
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span>&gt;Mark Birbeck&lt;/span&gt;, and
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span> <span class="hilite">resource=&quot;http://www.ivan-herman.net/foaf#me&quot;</span>&gt;Ivan Herman&lt;/span&gt;.
&lt;/p&gt;</pre>
<p>yielding:</p>
<pre class="example">@prefix bibo: &lt;http://purl.org/ontology/bibo/&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
[ a bibo:Chapter ;
dc:title &quot;Semantic Annotation and Retrieval&quot; ;
dc:creator ( &lt;http://ben.adida.net/#me&gt; &quot;Mark Birbeck&quot; &lt;http://www.ivan-herman.net/foaf#me&gt; ) .
...
]</pre>
<p>In the example above, <a class="aref" href="#A-rel" title="rel">@rel</a> could have been used leading
exactly to the same triples:</p>
<pre class="example">&lt;p prefix=&quot;bibo: http://purl.org/ontology/bibo/ dc: http://purl.org/dc/terms/ typeof=&quot;bibo:Chapter&quot;&gt;
“&lt;span property=&quot;dc:title&quot;&gt;Semantic Annotation and Retrieval&lt;/span&gt;”, by
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">rel=&quot;dc:creator&quot;</span> <span class="hilite">resource=&quot;http://ben.adida.net/#me&quot;</span>&gt;Ben Adida&lt;/span&gt;,
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">property=&quot;dc:creator&quot;</span>&gt;Mark Birbeck&lt;/span&gt;, and
&lt;span <span class="hilite">inlist=&quot;&quot;</span> <span class="hilite">rel=&quot;dc:creator&quot;</span> <span class="hilite">resource=&quot;http://www.ivan-herman.net/foaf#me&quot;</span>&gt;Ivan Herman&lt;/span&gt;.
&lt;/p&gt;</pre>
<p><a href="#s_Incomplete_Triples">Incomplete Triples</a> can also be
used in conjunction with lists when all list elements are resources
and not literal. For example, the previous example, this time with all
three authors referring to their FOAF profile, could have been written
as:</p>
<pre class="example">&lt;p prefix=&quot;bibo: http://purl.org/ontology/bibo/ dc: http://purl.org/dc/terms/ typeof=&quot;bibo:Chapter&quot;&gt;
“&lt;span property=&quot;dc:title&quot;&gt;Semantic Annotation and Retrieval&lt;/span&gt;”, by
&lt;span <span class="hilite">rel=&quot;dc:creator&quot;</span> <span class="hilite">inlist=&quot;&quot;</span>&gt;
&lt;a <span class="hilite">href=&quot;http://ben.adida.net/#me&quot;</span>&gt;Ben Adida&lt;/a&gt;,
&lt;a <span class="hilite">href=&quot;http://internet-apps.blogspot.com/2008/03/my-profile.html#me&quot;</span>&gt;Mark Birbeck&lt;/a&gt;, and
&lt;a <span class="hilite">href=&quot;http://www.ivan-herman.net/foaf#me&quot;</span>&gt;Ivan Herman&lt;/a&gt;.
&lt;/span&gt;
&lt;/p&gt;</pre>
<p>Resulting in:</p>
<pre class="example">@prefix bibo: &lt;http://purl.org/ontology/bibo/&gt; .
@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
[ a bibo:Chapter ;
dc:title &quot;Semantic Annotation and Retrieval&quot; ;
dc:creator ( &lt;http://ben.adida.net/#me&gt;
&lt;http://internet-apps.blogspot.com/2008/03/my-profile.html#me&gt;
&lt;http://www.ivan-herman.net/foaf#me&gt; ) .
...
]</pre>
<p>Note that it is also possible to generate an empty list easily,
without <a class="aref" href="#A-inlist" title="inlist">@inlist</a>, using:</p>
<pre class="example">&lt;span rel=&quot;prop&quot; resource=&quot;rdf:nil&quot;/&gt;</pre>
</div>
</div>
<div id="s_initialcontexts" typeof="bibo:Chapter" about="#s_initialcontexts" class="section">
<!-- OddPage -->
<h2><span class="secno">9. </span>RDFa Initial Contexts</h2>
<p>RDFa permits Host Languages to define an <a class="tref" title="initial-context" href="#T-initial-context">initial context</a>.
Such a context is a collection of terms, prefix mappings, and/or default
vocabulary declarations. An initial context is either intrinsically
known to the parser, or it is loaded as external documents and
processed. These documents <em class="rfc2119" title="must">must</em> be defined in an approved RDFa Host
Language (currently XML+RDFa and XHTML+RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>]). <span id="C16" about="#C16" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-10-21#resolution_2" rel="bibo:affirmedBy">
They <em class="rfc2119" title="may">may</em> also be defined in other formats (e.g., RDF/XML
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>], or Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>]).</span> When an initial
context document is processed, it is evaluated as follows:</p>
<ol>
<li>Parse the content (according to the processing rules for that
document type) and extract the triples into a collection associated
with that IRI. Note: These triples <em class="rfc2119" title="must not">must not</em> be co-mingled with the
triples being extracted from any other IRI. </li>
<li>For every subject with a pair of predicates that have the values <code>rdfa:prefix</code>
and <code>rdfa:uri</code>, create a key-value mapping from the <code>rdfa:prefix</code>
object literal (the key) to the <code>rdfa:uri</code> object literal
(the value). Add this mapping to the <a class="tref" title="list-of-iri-mappings" href="#T-list-of-iri-mappings">list of IRI mappings</a>
of the <a href="#s_sequence">initial evaluation context</a>, after
transforming the 'prefix' component to lower-case.</li>
<li>For every subject with a pair of predicates that have the values <code>rdfa:term</code>
and <code>rdfa:uri</code>, create a key-value mapping from the <code>rdfa:term</code>
object literal (the key) to the <code>rdfa:uri</code> object literal
(the value). Add this mapping to the <a class="tref" title="term-mappings" href="#T-term-mappings">term mappings</a> of
the <a href="#s_sequence">initial evaluation context</a>.</li>
<li>For an extracted triple that has a predicate of <code>rdfa:vocabulary</code>,
define the <a class="tref" title="default-vocabulary" href="#T-default-vocabulary">default vocabulary</a> of the <a href="#s_sequence">initial
evaluation context</a> to be the object literal of the <code>rdfa:vocabulary</code>
predicate.</li>
</ol>
<p id="C17" about="#C17" resource="http://www.w3.org/2010/02/rdfa/meetings/2010-10-21#resolution_2" rel="bibo:affirmedBy">
When an RDFa Initial Context is defined using an RDF serialization, it
<em class="rfc2119" title="must">must</em> use the vocabulary terms above to declare the components of the
context.</p>
<p class="note">Caching of the relevant triples retrieved via this
mechanism is <em class="rfc2119" title="recommended">recommended</em>. Embedding definitions for well known, stable
RDFa Initial Contexts in the implementation is <em class="rfc2119" title="recommended">recommended</em>.</p>
<p class="note">The object literal for the <code>rdfa:uri</code>
predicate <em class="rfc2119" title="must">must</em> be an absolute IRI. The object literal for the <code>rdfa:term</code>
predicate <em class="rfc2119" title="must">must</em> match the production for <a href="#P_term">term</a>. The
object literal for the <code>rdfa:prefix</code> predicate must match
the production for <a href="#P_prefix">prefix</a>. The object literal
for the <code>rdfa:vocabulary</code> predicate <em class="rfc2119" title="must">must</em> be an absolute IRI.
If one of the objects is not a Literal, does not match its associated
production, if there is more than one <code>rdfa:vocabulary</code>
predicate, or if there are additional <code>rdfa:uri</code> or <code>rdfa:term</code>
predicates sharing the same subject, an RDFa Processor <em class="rfc2119" title="must not">must not</em> create
the associated mapping.</p>
</div>
<div id="s_vocab_expansion" typeof="bibo:Chapter" about="#s_vocab_expansion" class="section">
<!-- OddPage -->
<h2><span class="secno">10. </span><dfn id="T-vocab-expansion">RDFa Vocabulary Expansion</dfn></h2>
<p> Since RDFa is based on RDF, the semantics of RDF vocabularies can be
used to gain more knowledge about data. Vocabularies, properties and
classes are identified by IRIs, which enables them to be discoverable.
RDF data published at the location of these IRIs can be retrieved, and
descriptions of the properties and classes using specified semantics can
be applied. </p>
<p> RDFa Vocabulary Expansion is an optional processing step which may be
added once the normal processing steps described in <a href="#s_model">Processing
Model</a> are complete. Vocabulary expansion relies on a very small
sub-set of OWL entailment [<cite><a class="bibref" rel="biblioentry" href="#bib-OWL2-OVERVIEW">OWL2-OVERVIEW</a></cite>] to add triples to the <a class="tref" title="output-graph" href="#T-output-graph">output
graph</a> based on rules and property/class relationships described
in referenced vocabularies. Vocabulary expansion <em class="rfc2119" title="may">may</em> be performed as
part of a larger RDF toolset including, for example, an OWL 2 RL
reasoner. Alternatively, using vocabulary data added to the <a class="tref" title="output-graph" href="#T-output-graph">output
graph</a> in processing step 2 of <a href="#s_sequence">Sequence</a>,
expansion <em class="rfc2119" title="may">may</em> also be done using a separate and dedicated (e.g., rule
based) reasoner after the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> has been generated,
or as the last processing step by an RDFa processor. </p>
<p> It can be very useful to make generalized data available for
subsequent usage of RDFa-embedded data by expanding inferred statements
entailed by these semantics. This provides for existing vocabularies
that extend well-known vocabularies to have those properties added to
the output graph automatically. For example, the namespace document of
the Creative Commons vocabulary, i.e., <code>http://creativecommons.org/ns</code>,
defines <code>cc:license</code> to be a sub-property of <code>dc:license</code>.
By using the <a class="aref" href="#A-vocab" title="vocab">@vocab</a> attribute, one can describe a licensing
information as follows:</p>
<pre class="example">This document is licensed under the
&lt;a vocab=&quot;http://creativecommons.org/ns#&quot;
rel=&quot;license&quot;
href=&quot;http://creativecommons.org/licenses/by-nc-nd/3.0/&quot;&gt;
Creative Commons By-NC-ND License
&lt;/a&gt;.</pre>
<p>which results in the following <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>:</p>
<pre class="example">@prefix cc: &lt;http://creativecommons.org/ns#&gt; .
@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
&lt;&gt; cc:license &lt;http://creativecommons.org/licenses/by-nc-nd/3.0/&gt; ;
rdfa:usesVocabulary &lt;http://creativecommons.org/ns#&gt; .</pre>
<p>After vocabulary expansion, the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> contains:</p>
<pre class="example">@prefix cc: &lt;http://creativecommons.org/ns#&gt; .
@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
<span class="hilite">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .</span>
&lt;&gt; cc:license &lt;http://creativecommons.org/licenses/by-nc-nd/3.0/&gt;;
<span class="hilite">dc:license &lt;http://creativecommons.org/licenses/by-nc-nd/3.0/&gt;</span> ;
rdfa:usesVocabulary &lt;http://creativecommons.org/ns#&gt; .</pre>
<p> Other vocabularies, specifically intended to provide relations to
multiple vocabularies, could also be defined by publishers, allowing use
of terms in a single namespace which result in properties and/or classes
from other primary vocabularies being imported. This benefits publishers
as data is now more widely searchable and encourages the practice of
referencing well-known vocabularies. </p>
<div class="informative section" id="s_vocab_expansion_details" typeof="bibo:Chapter" about="#s_vocab_expansion_details">
<h3><span class="secno">10.1 </span><dfn id="T-vocab_expansion_details">Details of the RDFa Vocabulary
Expansion</dfn></h3><p><em>This section is non-normative.</em></p>
<p> Once the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> is generated following the
processing steps defined in <a href="#s_sequence">Sequence</a>,
processors <em class="rfc2119" title="may">may</em> perform the following processing steps on the output
graph. It must do so only if the user of the processor explicitly asks
for it, as prescribed in <a href="#s_expansion_control">Vocabulary
Expansion Control of RDFa Processors</a>. </p>
<p> A <dfn title="vocabulary-graph" id="T-vocabulary-graph">vocabulary graph</dfn> is created as follows: For each IRI
being the object of a triple in the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a> with
the subject being the current document (<a class="tref" title="base" href="#T-base">base</a>) IRI and the
property being <code>rdfa:usesVocabulary</code>, that IRI is
dereferenced. If the dereferencing yields the serialization of an RDF
graph, that serialization is parsed and the resulting graph is merged
with the vocabulary graph. (An RDFa processor capable of vocabulary
expansion <em class="rfc2119" title="must">must</em> accept an RDF graph serialized in RDFa, and <em class="rfc2119" title="should">should</em>
accept other standard serialization formats of RDF such as RDF/XML
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>] and Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>].) </p>
<p class="note"> Note that if, in the second step, a particular
vocabulary is serialized in RDFa, that particular graph is not
expected to undergo any vocabulary expansion on its own. </p>
<p>Vocabulary expansion is then performed as follows:</p>
<ol>
<li>The processor operates on the merge of the default and vocabulary
graphs using <a href="#s_vocab_entailment">RDFa Vocabulary
Entailment</a>.</li>
<li>Add the new triples inferred from the <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>
using this entailment to the (expanded) <a class="tref" title="output-graph" href="#T-output-graph">output graph</a>.
The processor <em class="rfc2119" title="should not">should not</em> add the triples appearing in the <a class="tref" title="vocabulary-graph" href="#T-vocabulary-graph">vocabulary
graph</a> only.</li>
</ol>
<div class="explanation"> The goal of the second step is to avoid adding
the “axioms”, e.g., the sub-property definitions to the output graph.
Applications usually do not require those additional information. </div>
<div id="s_vocab_entailment" typeof="bibo:Chapter" about="#s_vocab_entailment" class="section">
<h4><span class="secno">10.1.1 </span><dfn id="T-vocab-entailment">RDFa Vocabulary Entailment</dfn></h4>
<p> For the purpose of vocabulary processing, RDFa used a very
restricted subset of the OWL vocabulary and is based on the RDF-Based
Semantics of OWL[<cite><a class="bibref" rel="biblioentry" href="#bib-OWL2-RDF-BASED-SEMANTICS">OWL2-RDF-BASED-SEMANTICS</a></cite>]. The RDFa
Vocabulary Entailment uses the following terms: </p>
<ul>
<li><code>rdf:type</code></li>
<li><code>rdfs:subClassOf</code></li>
<li><code>rdfs:subPropertyOf</code></li>
<li><code>owl:equivalentClass</code></li>
<li><code>owl:equivalentProperty</code><br />
</li>
</ul>
<p class="note">and it considers only the entailment on individuals
(i.e., not on the relationships that can be deduced on the
properties or the classes themselves.)<br />
</p>
<p class="note">While the formal definition of the RDFa Entailment
refers to the general OWL 2 Semantics, practical implementations may
rely on a subset of the OWL 2 RL Profile’s entailment expressed in
rules (<cite><a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/#Reasoning_in_OWL_2_RL_and_RDF_Graphs_using_Rules">section
4.3</a></cite> of [<cite><a class="bibref" rel="biblioentry" href="#bib-OWL2-PROFILES">OWL2-PROFILES</a></cite>]). In particular, the
relevant rules are (using the rule identifications in <cite><a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/#Reasoning_in_OWL_2_RL_and_RDF_Graphs_using_Rules">section
4.3</a></cite> of [<cite><a class="bibref" rel="biblioentry" href="#bib-OWL2-PROFILES">OWL2-PROFILES</a></cite>]): <code>prp-spo1</code>, <code>prp-eqp1</code>,
<code>prp-eqp2</code>, <code>cax-sco</code>, <code>cax-eqc1</code>,
and <code>cax-eqc2</code>. </p>
The entailment described in this section is the <em>minimum</em>
useful level for RDFa. Processors may, of course, choose to follow
more powerful entailment regimes, e.g., include full RDFS [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>]
or OWL [<cite><a class="bibref" rel="biblioentry" href="#bib-OWL2-OVERVIEW">OWL2-OVERVIEW</a></cite>] entailments. Using those entailments
applications may perform datatype validation by checking <code>rdfs:range</code>
of a property, or use the advanced facilities offered by, e.g., OWL’s
property chains to interlink vocabularies further. </div>
</div>
<div class="normative section" id="s_expansion_control" typeof="bibo:Chapter" about="#s_expansion_control">
<h3><span class="secno">10.2 </span>Vocabulary Expansion Control of RDFa Processors</h3>
<p> Conforming RDFa processors are NOT required to provide vocabulary
expansion. </p>
<p> If an RDFa processor provides vocabulary expansion, it <em class="rfc2119" title="must not">must not</em> be
performed by default. Instead, the processor <em class="rfc2119" title="must">must</em> provide an option, <code>vocab_expansion</code>,
which, when used, instructs the RDFa processor to perform a vocabulary
expansion before returning the output graph. </p>
<p class="note"> Although vocabulary expansion is described in terms of
a <a class="tref" title="vocabulary-graph" href="#T-vocabulary-graph">vocabulary graph</a> and RDFS entailment rules, processors
are free to use any process which obtains equivalent results. </p>
<div class="informative section" id="s_vocab_guidelines" typeof="bibo:Chapter" about="#s_vocab_guidelines">
<h4><span class="secno">10.2.1 </span>Notes to RDFa Vocabulary Implementations and Publishing</h4><p><em>This section is non-normative.</em></p>
<p>For RDFa Processors caching the relevant graphs retrieved via this
mechanism is <em class="rfc2119" title="recommended">recommended</em>. Caching is usually based on HTTP response
headers like expiration time, cache control, etc.</p>
<p>For publishers of vocabularies, the URI for the vocabularies <em class="rfc2119" title="should">should</em>
be dereferencable, and should return an RDF graph with the
vocabulary description. This vocabulary description <em class="rfc2119" title="should">should</em> be
available encoded in RDFa, and <em class="rfc2119" title="may">may</em> also be available in other RDF
serialization syntaxes (using content negotiation to choose among
the different formats). If possible, vocabulary descriptions <em class="rfc2119" title="should">should</em>
include subproperty and subclass statements linking the vocabulary
terms to other, well-known vocabularies. Finally, HTTP responses
<em class="rfc2119" title="should">should</em> include fields usable for cache control, e.g., expiration
date.</p>
</div>
</div>
</div>
<div class="appendix section" id="s_datatypes" typeof="bibo:Chapter" about="#s_datatypes">
<!-- OddPage -->
<h2><span class="secno">A. </span>CURIE Datatypes</h2>
<p>In order to facilitate the use of CURIEs in markup languages, this
specification defines some additional datatypes in the XHTML datatype
space (<code>http://www.w3.org/1999/xhtml/datatypes/</code>). Markup
languages that want to import these definitions can find them in the
&quot;datatypes&quot; file for their schema grammar:</p>
<ul>
<li><a href="http://www.w3.org/MarkUp/DTD/xhtml-datatypes-1.mod">DTD
xhtml-datatypes.mod</a></li>
<li><a href="http://www.w3.org/MarkUp/SCHEMA/xhtml-datatypes-1.xsd">XML
Schema xhtml-datatypes.xsd</a></li>
</ul>
<p>Specifically, the following datatypes are defined:</p>
<dl>
<dt><dfn id="dfn-curie">CURIE</dfn></dt>
<dd>A single <a href="#P_curie">curie</a></dd>
<dt><dfn id="dfn-curies">CURIEs</dfn></dt>
<dd>A white space separated list of CURIEs</dd>
<dt><dfn id="dfn-curieoriri">CURIEorIRI</dfn></dt>
<dd>A <a class="datatype internalDFN" title="CURIE" href="#dfn-curie">CURIE</a> or a <a class="externalDFN" title="IRI">IRI</a></dd>
<dt><dfn id="dfn-curieoriris">CURIEorIRIs</dfn></dt>
<dd>A white space separated list of <a class="datatype internalDFN" title="CURIEorIRI" href="#dfn-curieoriri">CURIEorIRI</a>s</dd>
<dt><dfn id="dfn-safecurie">SafeCURIE</dfn></dt>
<dd>A single <a href="#P_safe_curie">safe_curie</a></dd>
<dt><dfn id="dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</dfn></dt>
<dd>A single <a class="datatype internalDFN" title="SafeCURIE" href="#dfn-safecurie">SafeCURIE</a> or <a class="datatype internalDFN" title="CURIEorIRI" href="#dfn-curieoriri">CURIEorIRI</a></dd>
<dt><dfn id="dfn-safecurieorcurieoriris">SafeCURIEorCURIEorIRIs</dfn></dt>
<dd>A white space separated list of <a class="datatype internalDFN" title="SafeCURIEorCURIEorIRI" href="#dfn-safecurieorcurieoriri">SafeCURIEorCURIEorIRI</a>s.</dd>
<dt><dfn id="dfn-term">TERM</dfn></dt>
<dd>A single <a href="#P_term">term</a></dd>
<dt><dfn id="dfn-termorcurieorabsiri">TERMorCURIEorAbsIRI</dfn></dt>
<dd>A <a class="datatype internalDFN" title="TERM" href="#dfn-term">TERM</a> or a <a class="datatype internalDFN" title="CURIEorIRI" href="#dfn-curieoriri">CURIEorIRI</a></dd>
<dt><dfn id="dfn-termorcurieorabsiris">TERMorCURIEorAbsIRIs</dfn></dt>
<dd>A white space separated list of <a class="datatype internalDFN" title="TERMorCURIEorAbsIRI" href="#dfn-termorcurieorabsiri">TERMorCURIEorAbsIRI</a>s</dd>
</dl>
<div class="informative section" id="xml-schema-definition" typeof="bibo:Chapter" about="#xml-schema-definition">
<h3><span class="secno">A.1 </span>XML Schema Definition</h3><p><em>This section is non-normative.</em></p>
<p>The following <i>informative</i> XML Schema definition for these
datatypes is included as an example:</p>
<pre class="example">&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
&lt;xs:schema
xmlns:xs=&quot;http://www.w3.org/2001/XMLSchema&quot;
xmlns=&quot;http://www.w3.org/1999/xhtml/datatypes/&quot;
xmlns:xh11d=&quot;http://www.w3.org/1999/xhtml/datatypes/&quot;
targetNamespace=&quot;http://www.w3.org/1999/xhtml/datatypes/&quot;
elementFormDefault=&quot;qualified&quot;
&gt;
&lt;xs:simpleType name=&quot;CURIE&quot;&gt;
&lt;xs:restriction base=&quot;xs:string&quot;&gt;
&lt;xs:pattern value=&quot;(([\i-[:]][\c-[:]]*)?:)?.+&quot; /&gt;
&lt;xs:minLength value=&quot;1&quot;/&gt;
&lt;/xs:restriction&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;CURIEs&quot;&gt;
&lt;xs:list itemType=&quot;xh11d:CURIE&quot;/&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;SafeCURIE&quot;&gt;
&lt;xs:restriction base=&quot;xs:string&quot;&gt;
&lt;xs:pattern value=&quot;\[(([\i-[:]][\c-[:]]*)?:)?.+\]&quot; /&gt;
&lt;xs:minLength value=&quot;3&quot;/&gt;
&lt;/xs:restriction&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;SafeCURIEs&quot;&gt;
&lt;xs:list itemType=&quot;xh11d:SafeCURIE&quot;/&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;TERM&quot;&gt;
&lt;xs:restriction base=&quot;xs:Name&quot;&gt;
&lt;xs:pattern value=&quot;[\i-[:]][/\c-[:]]*&quot; /&gt;
&lt;/xs:restriction&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;CURIEorIRI&quot;&gt;
&lt;xs:union memberTypes=&quot;xh11d:CURIE xs:anyURI&quot; /&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;CURIEorIRIs&quot;&gt;
&lt;xs:list itemType=&quot;xh11d:CURIEorIRI&quot;/&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;SafeCURIEorCURIEorIRI&quot;&gt;
&lt;xs:union memberTypes=&quot;xh11d:SafeCURIE xh11d:CURIE xs:anyURI&quot; /&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;SafeCURIEorCURIEorIRIs&quot;&gt;
&lt;xs:list itemType=&quot;xh11d:SafeCURIEorCURIEorIRI&quot;/&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name='AbsIRI'&gt;
&lt;xs:restriction base='xs:string'&gt;
&lt;xs:pattern value=&quot;[\i-[:]][\c-[:]]+:.+&quot; /&gt;
&lt;/xs:restriction&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;TERMorCURIEorAbsIRI&quot;&gt;
&lt;xs:union memberTypes=&quot;xh11d:TERM xh11d:CURIE xh11d:AbsIRI&quot; /&gt;
&lt;/xs:simpleType&gt;
&lt;xs:simpleType name=&quot;TERMorCURIEorAbsIRIs&quot;&gt;
&lt;xs:list itemType=&quot;xh11d:SafeCURIEorCURIEorAbsIRI&quot;/&gt;
&lt;/xs:simpleType&gt;
&lt;/xs:schema&gt;</pre> </div>
<div class="informative section" id="xml-dtd-definition" typeof="bibo:Chapter" about="#xml-dtd-definition">
<h3><span class="secno">A.2 </span>XML DTD Definition</h3><p><em>This section is non-normative.</em></p>
<p>The following <i>informative</i> XML DTD definition for these
datatypes is included as an example:</p>
<pre class="example">&lt;!ENTITY % CURIE.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % CURIEs.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % CURIEorIRI.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % CURIEorIRIs.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % SafeCURIEorCURIEorIRI.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % SafeCURIEorCURIEorIRIs.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % TERMorCURIEorAbsIRI.datatype &quot;CDATA&quot; &gt;
&lt;!ENTITY % TERMorCURIEorAbsIRIs.datatype &quot;CDATA&quot; &gt;</pre> </div>
</div>
<div class="normative section" id="vocabulary" typeof="bibo:Chapter" about="#vocabulary">
<!-- OddPage -->
<h2><span class="secno">B. </span>The RDFa Vocabulary</h2>
<p>The RDFa Vocabulary has three roles: it contains the predicates to
define the terms and prefixes in <a class="tref" title="initial-context" href="#T-initial-context">initial context</a>
documents, it contains the classes and predicates for the messages that
a <a class="tref" title="processor-graph" href="#T-processor-graph">processor graph</a> may contain and, finally, it contains
the predicate necessary for vocabulary processing. The IRI of the
vocabulary is <code>http://www.w3.org/ns/rdfa#</code>; the usual prefix
used in this document is <code>rdfa</code>.</p>
<p>This vocabulary specification is available in <a href="http://www.w3.org/ns/rdfa.html">XHTML+RDFa
1.1</a>, <a href="http://www.w3.org/ns/rdfa.ttl">Turtle</a>, and in <a href="http://www.w3.org/ns/rdfa.rdf">RDF/XML</a>
formats.</p>
<div class="normative section" id="term-prefix-definitions-vocabulary" typeof="bibo:Chapter" about="#term-prefix-definitions-vocabulary">
<h3><span class="secno">B.1 </span>Term and Prefix Assignments</h3>
<p>The RDFa Vocabulary includes the following triples (shown here in
Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>] format): </p>
<pre class="example">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix owl: &lt;http://www.w3.org/2002/07/owl#&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
@prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt; .
@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .
&lt;http://www.w3.org/ns/rdfa#&gt; a owl:Ontology .
rdfa:PrefixOrTermMapping a rdfs:Class, owl:Class ;
dc:description &quot;is the top level class for prefix or term mappings&quot; .
rdfa:PrefixMapping dc:description &quot;is the class for prefix mappings&quot; .
rdfs:subClassOf rdfa:PrefixOrTermMapping .
rdfa:TermMapping dc:description &quot;is the class for term mappings&quot; .
rdfs:subClassOf rdfa:PrefixOrTermMapping .
rdfa:prefix a rdf:Property, owl:DatatypeProperty ;
rdfs:domain rdfa:PrefixMapping ;
dc:description &quot;defines a prefix mapping for an IRI; the value is supposed to be a NMTOKEN&quot; .
rdfa:term a rdf:Property, owl:DatatypeProperty ;
rdfs:domain rdfa:TermMapping ;
dc:description &quot;defines a term mapping for an IRI; the value is supposed to be a NMTOKEN&quot; .
rdfa:uri a rdf:Property, owl:DatatypeProperty ;
rdfs:domain rdfa:PrefixOrTermMapping ;
dc:description &quot;&quot;&quot;defines the IRI for either a prefix or a term mapping;
the value is supposed to be an absolute IRI&quot;&quot;&quot; .
rdfa:vocabulary a rdf:Property, owl:DatatypeProperty ;
dc:description &quot;&quot;&quot;defines an IRI to be used as a default vocabulary;
the value is can be any string; for documentation purposes it is advised to use
the string ‘true’ or ‘True’.&quot;&quot;&quot; . </pre>
<p>These predicates can be used to define the <a class="tref" title="initial-context" href="#T-initial-context">initial context</a>
for a given Host Language.</p>
<p>These predicates are used to 'pair' IRI strings and their usage in
the form of a prefix and/or a term as part of, for example, a blank
node. An example can be as follows:</p>
<pre class="example">[] rdfa:uri &quot;http://xmlns.com/foaf/0.1/name&quot; ;
rdfa:prefix &quot;foaf&quot; . </pre>
<p>which defines a prefix for the foaf IRI.</p>
</div>
<div class="normative section" id="processor-graph-reporting" typeof="bibo:Chapter" about="#processor-graph-reporting">
<h3><span class="secno">B.2 </span>Processor Graph Reporting</h3>
<p>The Vocabulary includes the following term definitions (shown here in
Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>] format): </p>
<pre class="example">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix owl: &lt;http://www.w3.org/2002/07/owl#&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
@prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt; .
@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
rdfa:PGClass a rdfs:Class, owl:Class;
dc:description &quot;is the top level class of the hierarchy&quot; .
rdfa:Error dcterms:description &quot;is the class for all error conditions&quot;;
rdfs:subClassOf rdfa:PGClass .
rdfa:Warning dcterms:description &quot;is the class for all warnings&quot;;
rdfs:subClassOf rdfa:PGClass .
rdfa:Info dcterms:description &quot;is the class for all informations&quot;;
rdfs:subClassOf rdfa:PGClass .
rdfa:DocumentError dc:description &quot;error condition; to be used when the document
fails to be fully processed as a result of non-conformant host language markup&quot;;
rdfs:subClassOf rdfa:Error .
rdfa:VocabReferenceError dc:description &quot;warning; to be used
when the value of a @vocab attribute cannot be dereferenced, hence the vocabulary expansion
cannot be completed.&quot;;
rdfs:subClassOf rdfa:Warning .
rdfa:UnresolvedTerm dc:description &quot;warning; to be used when a Term fails to be resolved&quot;;
rdfs:subClassOf rdfa:Warning .
rdfa:UnresolvedCURIE dc:description &quot;warning; to be used when a CURIE prefix
fails to be resolved&quot;;
rdfs:subClassOf rdfa:Warning .
rdfa:context a owl:ObjectProperty, rdf:Property;
dc:description &quot;provides extra context for the error, e.g., http response,
an XPointer/XPath information, or simply the IRI that created the error&quot;;
rdfs:domain rdfa:PGClass .</pre> </div>
<div class="normative section" id="vocabulary-relationship" typeof="bibo:Chapter" about="#vocabulary-relationship">
<h3><span class="secno">B.3 </span>Term for vocabulary expansion</h3>
<p>The Vocabulary includes the following term definitions (shown here in
Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>] format): </p>
<pre class="example">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix owl: &lt;http://www.w3.org/2002/07/owl#&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
@prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
rdfa:usesVocabulary a owl:ObjectProperty, rdf:Property;
dc:description &quot;provides a relationship between the host document and a vocabulary
defined using the @vocab facility of RDFa1.1&quot; .</pre> </div>
<div class="informative section" id="a_history" typeof="bibo:Chapter" about="#a_history">
<h3><span class="secno">B.4 </span>Changes</h3><p><em>This section is non-normative.</em></p>
<div id="major-differences-with-rdfa-syntax-1.0" typeof="bibo:Chapter" about="#major-differences-with-rdfa-syntax-1.0" class="section">
<h4><span class="secno">B.4.1 </span>Major differences with RDFa Syntax 1.0</h4>
<p>This specification introduces a number of new features, and extends
the behavior of some features from the previous version. The
following summary may be helpful to RDFa Processor developers, but
is <em>not</em> meant to be comprehensive.</p>
<ul>
<li>Specific rules about XHTML have been moved into a companion
specification: [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML-RDFA">XHTML-RDFA</a></cite>].</li>
<li>Prefix mappings can now be declared using <a class="aref" href="#A-prefix" title="prefix">@prefix</a>
in addition to <span class="aref">@xmlns</span>. The usage of <span class="aref">@xmlns</span>
has been deprecated.</li>
<li>Prefix names are now required be be converted to lower-case when
the mapping is defined. Prefixes are checked in a case-insensitive
manner during CURIE expansion.</li>
<li>You can now use an Absolute IRI everywhere you could previously
only use a CURIE (e.g., in the value of <a class="aref" href="#A-datatype" title="datatype">@datatype</a>).</li>
<li>There is now a concept of a <a class="tref" title="term" href="#T-term">term</a>. This concept has
replaced the concept of a 'reserved word'. It is possible now to
use a 'term' in most places where you could previously only use a
CURIE.</li>
<li>You can define a default prefix mapping (via <a class="aref" href="#A-vocab" title="vocab">@vocab</a>)
that will be used on undefined terms.</li>
<li>When a triple would include an object literal, and there is no
explicit datatype attribute, the object literal will now be a
'plain literal'. In version 1.0 it would have been an
'XMLLiteral'.</li>
<li>The <a class="aref" href="#A-inlist" title="inlist">@inlist</a> attribute can be used to instruct the
processor to generate RDF lists with the resources rather than
simple triples.</li>
<li>The effect of <a class="aref" href="#A-src" title="src">@src</a> is now identical to <a class="aref" href="#A-href" title="href">@href</a>
rather than <a class="aref" href="#A-about" title="about">@about</a> like in version 1.0. </li>
</ul>
<p>While this specification strives to be as backward compatible as
possible with [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-SYNTAX">RDFA-SYNTAX</a></cite>], the changes above mean that there are
some circumstances where it is possible for different RDF triples to
be output for the same document when processed by an RDFa 1.0
processor vs. an RDFa 1.1 processor. In order to minimize these
differences, a document author can do the following:</p>
<ul>
<li>Use the XHTML+RDFa 1.0 document type as defined in
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-SYNTAX">RDFA-SYNTAX</a></cite>].</li>
<li>Place a <span class="aref">@version</span> attribute with the
value <code>XHTML+RDFa 1.0</code> on the <code>html</code>
element.</li>
<li>If there are places in the document where an object literal <em class="rfc2119" title="must">must</em>
be an XMLLiteral, use <code>datatype='rdf:XMLLiteral'</code>.</li>
<li>If there are places in the document where an object literal <em class="rfc2119" title="must">must</em>
be a plain literal, use <code>datatype=''</code>.</li>
<li>If there are places in the document where <a class="aref" href="#A-src" title="src">@src</a> is
used, add an <a class="aref" href="#A-about" title="about">@about</a> (unless already present) with the
same URI.</li>
</ul>
<p>When producing XHTML+RDFa 1.1 documents, it is possible to reduce
the incompatibilities with RDFa 1.0 conforming processors by doing
the following:</p>
<ul>
<li>DO NOT use the <a class="aref" href="#A-vocab" title="vocab">@vocab</a> feature.</li>
<li>DO NOT rely upon host language defaults for IRI mappings.</li>
<li>DO NOT use absolute IRIs in place of CURIEs.</li>
<li>Use <span class="aref">@xmlns</span> AND <a class="aref" href="#A-prefix" title="prefix">@prefix</a>
when declaring prefix mappings.</li>
<li>DO NOT use TERMs on <a class="aref" href="#A-datatype" title="datatype">@datatype</a>, <a class="aref" href="#A-property" title="property">@property</a>,
or <a class="aref" href="#A-typeof" title="typeof">@typeof</a>.</li>
<li>When using TERMs in <a class="aref" href="#A-rel" title="rel">@rel</a> and <a class="aref" href="#A-rev" title="rev">@rev</a>,
only use ones defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-SYNTAX">RDFA-SYNTAX</a></cite>].</li>
<li>Place a <span class="aref">version</span> attribute with the
value <code>XHTML+RDFa 1.0</code> on the <code>html</code>
element.</li>
<li>If there are places in the document where an object literal <em class="rfc2119" title="must">must</em>
be an XMLLiteral, use <code>datatype='rdf:XMLLiteral'</code>.</li>
<li>If there are places in the document where an object literal <em class="rfc2119" title="must">must</em>
be a plain literal, use <code>datatype=''</code>.</li>
<li>If there are places in the document where <a class="aref" href="#A-src" title="src">@src</a> is
used, add an <a class="aref" href="#A-about" title="about">@about</a> (unless already present) with the
same URI.</li>
</ul>
</div>
</div>
</div>
<div class="informative section" id="a_acks" typeof="bibo:Chapter" about="#a_acks">
<!-- OddPage -->
<h2><span class="secno">C. </span>Acknowledgments</h2><p><em>This section is non-normative.</em></p>
<p>At the time of publication, the active members of the RDFa Working
Group were:</p>
<ul>
<li>Ben Adida, Creative Commons (Chair)</li>
<li>Benjamin Adrian, German Research Center for Artificial Intelligence
(DFKI) Gmbh</li>
<li>Mark Birbeck, webBackplane.com (Invited Expert)</li>
<li>Stéphane Corlosquet, Massachusetts General Hospital</li>
<li>Markus Gylling, DAISY Consortium</li>
<li>Ivan Herman, <acronym title="World Wide Web Consortium">W3C</acronym></li>
<li>Toby Inkster (Invited Expert)</li>
<li>Gregg Kellogg (Invited Expert)</li>
<li>Niklas Lindström (Invited Expert)</li>
<li>Shane McCarron, Applied Testing and Technology, Inc. (Invited
Expert)</li>
<li>Knud Möller, DERI Galway at the National University of Ireland</li>
<li>John O'Donovan, British Broadcasting Corporation</li>
<li>Steven Pemberton, Centre for Mathematics and Computer Science (CWI)</li>
<li>Nathan Rixham (Invited Expert)</li>
<li>Manu Sporny, Digital Bazaar (Chair, Invited Expert)</li>
<li>Robert Weir, IBM Corporation</li>
</ul>
</div>
<div id="references" class="appendix section" typeof="bibo:Chapter" about="#references">
<!-- OddPage -->
<h2><span class="secno">D. </span>References</h2><div id="normative-references" typeof="bibo:Chapter" about="#normative-references" class="section"><h3><span class="secno">D.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-OWL2-OVERVIEW">[OWL2-OVERVIEW]</dt><dd rel="dcterms:requires">W3C OWL Working Group. <a href="http://www.w3.org/TR/2009/REC-owl2-overview-20091027/"><cite>OWL 2 Web Ontology Language: Overview.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-overview-20091027/">http://www.w3.org/TR/2009/REC-owl2-overview-20091027/</a>
</dd><dt id="bib-OWL2-PROFILES">[OWL2-PROFILES]</dt><dd rel="dcterms:requires">Boris Motik; Bernardo Cuenca Grau; Ian Horrocks; Zhe Wu; Achille Fokoue; Carsten Lutz. <a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/"><cite>OWL 2 Web Ontology Language:Profiles.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/">http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/</a>
</dd><dt id="bib-OWL2-RDF-BASED-SEMANTICS">[OWL2-RDF-BASED-SEMANTICS]</dt><dd rel="dcterms:requires">Michael Schneider. <a href="http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/"><cite>OWL 2 Web Ontology Language:RDF-Based Semantics.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/">http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/</a>
</dd><dt id="bib-RDF-MT">[RDF-MT]</dt><dd rel="dcterms:requires">Patrick Hayes. <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210"><cite>RDF Semantics.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210">http://www.w3.org/TR/2004/REC-rdf-mt-20040210</a>
</dd><dt id="bib-RDF-SYNTAX-GRAMMAR">[RDF-SYNTAX-GRAMMAR]</dt><dd rel="dcterms:requires">Dave Beckett. <a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210"><cite>RDF/XML Syntax Specification (Revised).</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210">http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210</a>
</dd><dt id="bib-RFC2119">[RFC2119]</dt><dd rel="dcterms:requires">S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate Requirement Levels.</cite></a> March 1997. Internet RFC 2119. URL: <a href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
</dd><dt id="bib-RFC3987">[RFC3987]</dt><dd rel="dcterms:requires">M. Dürst; M. Suignard. <a href="http://www.ietf.org/rfc/rfc3987.txt"><cite>Internationalized Resource Identifiers (IRIs).</cite></a> January 2005. Internet RFC 3987. URL: <a href="http://www.ietf.org/rfc/rfc3987.txt">http://www.ietf.org/rfc/rfc3987.txt</a>
</dd><dt id="bib-TURTLE">[TURTLE]</dt><dd rel="dcterms:requires">David Beckett, Tim Berners-Lee. <a href="http://www.w3.org/TeamSubmission/turtle/"><cite>Turtle: Terse RDF Triple Language.</cite></a> January 2008. W3C Team Submission. URL: <a href="http://www.w3.org/TeamSubmission/turtle/">http://www.w3.org/TeamSubmission/turtle/</a>
</dd><dt id="bib-XHTML-RDFA">[XHTML-RDFA]</dt><dd rel="dcterms:requires">Shane McCarron; et. al. <a href="http://www.w3.org/TR/2011/WD-xhtml-rdfa-20111215"><cite>XHTML+RDFa 1.1.</cite></a> 15 December 2011. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2011/WD-xhtml-rdfa-20111215">http://www.w3.org/TR/2011/WD-xhtml-rdfa-20111215</a>
</dd><dt id="bib-XML-NAMES">[XML-NAMES]</dt><dd rel="dcterms:requires">Richard Tobin; et al. <a href="http://www.w3.org/TR/2009/REC-xml-names-20091208/"><cite>Namespaces in XML 1.0 (Third Edition).</cite></a> 8 December 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-xml-names-20091208/">http://www.w3.org/TR/2009/REC-xml-names-20091208/</a>
</dd><dt id="bib-XML10-4e">[XML10-4e]</dt><dd rel="dcterms:requires">C. M. Sperberg-McQueen; et al. <a href="http://www.w3.org/TR/2006/REC-xml-20060816/"><cite>Extensible Markup Language (XML) 1.0 (Fourth Edition).</cite></a> 16 August 2006. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2006/REC-xml-20060816/">http://www.w3.org/TR/2006/REC-xml-20060816/</a>
</dd><dt id="bib-XMLSCHEMA-2">[XMLSCHEMA-2]</dt><dd rel="dcterms:requires">Paul V. Biron; Ashok Malhotra. <a href="http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/"><cite>XML Schema Part 2: Datatypes Second Edition.</cite></a> 28 October 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/">http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/</a>
</dd></dl></div><div id="informative-references" typeof="bibo:Chapter" about="#informative-references" class="section"><h3><span class="secno">D.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-HTML401">[HTML401]</dt><dd rel="dcterms:references">David Raggett; Ian Jacobs; Arnaud Le Hors. <a href="http://www.w3.org/TR/1999/REC-html401-19991224"><cite>HTML 4.01 Specification.</cite></a> 24 December 1999. W3C Recommendation. URL: <a href="http://www.w3.org/TR/1999/REC-html401-19991224">http://www.w3.org/TR/1999/REC-html401-19991224</a>
</dd><dt id="bib-MICROFORMATS">[MICROFORMATS]</dt><dd rel="dcterms:references"><a href="http://microformats.org"><cite>Microformats</cite></a>. URL: <a href="http://microformats.org">http://microformats.org</a>
</dd><dt id="bib-QNAMES">[QNAMES]</dt><dd rel="dcterms:references">N. Walsh. <a href="http://www.w3.org/2001/tag/doc/qnameids-2004-03-17"><cite>Using Qualified Names (QNames) as Identifiers in XML Content</cite></a> 17 March, 2004. TAG Finding. URL: <a href="http://www.w3.org/2001/tag/doc/qnameids-2004-03-17">http://www.w3.org/2001/tag/doc/qnameids-2004-03-17</a>
</dd><dt id="bib-RDF-CONCEPTS">[RDF-CONCEPTS]</dt><dd rel="dcterms:references">Graham Klyne; Jeremy J. Carroll. <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210"><cite>Resource Description Framework (RDF): Concepts and Abstract Syntax.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210">http://www.w3.org/TR/2004/REC-rdf-concepts-20040210</a>
</dd><dt id="bib-RDF-PRIMER">[RDF-PRIMER]</dt><dd rel="dcterms:references">Frank Manola; Eric Miller. <a href="http://www.w3.org/TR/2004/REC-rdf-primer-20040210/"><cite>RDF Primer.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-primer-20040210/">http://www.w3.org/TR/2004/REC-rdf-primer-20040210/</a>
</dd><dt id="bib-RDF-SYNTAX">[RDF-SYNTAX]</dt><dd rel="dcterms:references">Ora Lassila; Ralph R. Swick. <a href="http://www.w3.org/TR/1999/REC-rdf-syntax-19990222"><cite>Resource Description Framework (RDF) Model and Syntax Specification.</cite></a> 22 February 1999. W3C Recommendation. URL: <a href="http://www.w3.org/TR/1999/REC-rdf-syntax-19990222">http://www.w3.org/TR/1999/REC-rdf-syntax-19990222</a>
</dd><dt id="bib-RDF-TESTCASES">[RDF-TESTCASES]</dt><dd rel="dcterms:references">Jan Grant; Dave Beckett. <a href="http://www.w3.org/TR/2004/REC-rdf-testcases-20040210"><cite>RDF Test Cases.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-testcases-20040210">http://www.w3.org/TR/2004/REC-rdf-testcases-20040210</a>
</dd><dt id="bib-RDFA-PRIMER">[RDFA-PRIMER]</dt><dd rel="dcterms:references">Mark Birbeck; Ben Adida. <a href="http://www.w3.org/TR/2008/NOTE-xhtml-rdfa-primer-20081014"><cite>RDFa Primer.</cite></a> 14 October 2008. W3C Note. URL: <a href="http://www.w3.org/TR/2008/NOTE-xhtml-rdfa-primer-20081014">http://www.w3.org/TR/2008/NOTE-xhtml-rdfa-primer-20081014</a>
</dd><dt id="bib-RDFA-SYNTAX">[RDFA-SYNTAX]</dt><dd rel="dcterms:references">Ben Adida, et al. <a href="http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014"><cite>RDFa in XHTML: Syntax and Processing.</cite></a> 14 October 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014">http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014</a>
</dd><dt id="bib-RELAXNG-SCHEMA">[RELAXNG-SCHEMA]</dt><dd rel="dcterms:references"><a href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052348_ISO_IEC_19757-2_2008(E).zip"><cite>Information technology -- Document Schema Definition Language (DSDL) -- Part 2: Regular-grammar-based validation -- RELAX NG</cite></a>. ISO/IEC 19757-2:2008. URL: <a href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052348_ISO_IEC_19757-2_2008(E).zip">http://standards.iso.org/ittf/PubliclyAvailableStandards/c052348_ISO_IEC_19757-2_2008(E).zip</a>
</dd><dt id="bib-RFC2854">[RFC2854]</dt><dd rel="dcterms:references">D. Connolly; L. Masinter. <a href="http://www.rfc-editor.org/rfc/rfc2854.txt"><cite>The 'text/html' Media Type.</cite></a> June 2000. Internet RFC 2854. URL: <a href="http://www.rfc-editor.org/rfc/rfc2854.txt">http://www.rfc-editor.org/rfc/rfc2854.txt</a>
</dd><dt id="bib-RFC3023">[RFC3023]</dt><dd rel="dcterms:references">M. Murata; S. St.Laurent; D. Kohn. <a href="http://www.ietf.org/rfc/rfc3023.txt"><cite>XML Media Types</cite></a> January 2001. Internet RFC 3023. URL: <a href="http://www.ietf.org/rfc/rfc3023.txt">http://www.ietf.org/rfc/rfc3023.txt</a>
</dd><dt id="bib-RFC3986">[RFC3986]</dt><dd rel="dcterms:references">T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifier (URI): Generic Syntax.</cite></a> January 2005. Internet RFC 3986. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a>
</dd><dt id="bib-SAX">[SAX]</dt><dd rel="dcterms:references">D. Megginson, et al. <a href="http://www.megginson.com/downloads/SAX/"><cite>SAX: The Simple API for XML</cite></a>. May 1998. URL: <a href="http://www.megginson.com/downloads/SAX/"> http://www.megginson.com/downloads/SAX/</a>
</dd><dt id="bib-WEBARCH">[WEBARCH]</dt><dd rel="dcterms:references">Norman Walsh; Ian Jacobs. <a href="http://www.w3.org/TR/2004/REC-webarch-20041215/"><cite>Architecture of the World Wide Web, Volume One.</cite></a> 15 December 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-webarch-20041215/">http://www.w3.org/TR/2004/REC-webarch-20041215/</a>
</dd><dt id="bib-XHTML11">[XHTML11]</dt><dd rel="dcterms:references">Murray Altheim; Shane McCarron. <a href="http://www.w3.org/TR/2001/REC-xhtml11-20010531"><cite>XHTML™ 1.1 - Module-based XHTML.</cite></a> 31 May 2001. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2001/REC-xhtml11-20010531">http://www.w3.org/TR/2001/REC-xhtml11-20010531</a>
</dd><dt id="bib-XML-EXC-C14N">[XML-EXC-C14N]</dt><dd rel="dcterms:references">Donald E. Eastlake 3rd; Joseph Reagle; John Boyer. <a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/"><cite>Exclusive XML Canonicalization Version 1.0.</cite></a> 18 July 2002. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/">http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/</a>
</dd><dt id="bib-XML10">[XML10]</dt><dd rel="dcterms:references">C. M. Sperberg-McQueen; et al. <a href="http://www.w3.org/TR/2008/REC-xml-20081126/"><cite>Extensible Markup Language (XML) 1.0 (Fifth Edition).</cite></a> 26 November 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2008/REC-xml-20081126/">http://www.w3.org/TR/2008/REC-xml-20081126/</a>
</dd><dt id="bib-XMLSCHEMA-1">[XMLSCHEMA-1]</dt><dd rel="dcterms:references">Henry S. Thompson; et al. <a href="http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/"><cite>XML Schema Part 1: Structures Second Edition.</cite></a> 28 October 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/">http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/</a>
</dd></dl></div></div></body></html>