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.
1591 lines
83 KiB
1591 lines
83 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01+RDFa 1.1//EN"
|
|
"http://www.w3.org/MarkUp/DTD/html401-rdfa11-1.dtd">
|
|
<html lang="en" dir="ltr" about="" property="dcterms:language" content="en" prefix="dcterms: http://purl.org/dc/terms/ bibo: http://purl.org/ontology/bibo/ foaf: http://xmlns.com/foaf/0.1/ xsd: http://www.w3.org/2001/XMLSchema#">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<title>RDF 1.1 Concepts and Abstract Syntax</title>
|
|
<style type="text/css">
|
|
.figure { font-weight: bold; text-align: center; }
|
|
</style>
|
|
|
|
|
|
<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: 1px 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;
|
|
margin: 1em 0em 0em;
|
|
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 {
|
|
margin: 1em 0em 0em;
|
|
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;
|
|
}
|
|
|
|
/* --- Best Practices --- */
|
|
div.practice {
|
|
border: solid #bebebe 1px;
|
|
margin: 2em 1em 1em 2em;
|
|
}
|
|
|
|
span.practicelab {
|
|
margin: 1.5em 0.5em 1em 1em;
|
|
font-weight: bold;
|
|
font-style: italic;
|
|
}
|
|
|
|
span.practicelab { background: #dfffff; }
|
|
|
|
span.practicelab {
|
|
position: relative;
|
|
padding: 0 0.5em;
|
|
top: -1.5em;
|
|
}
|
|
|
|
p.practicedesc {
|
|
margin: 1.5em 0.5em 1em 1em;
|
|
}
|
|
|
|
@media screen {
|
|
p.practicedesc {
|
|
position: relative;
|
|
top: -2em;
|
|
padding: 0;
|
|
margin: 1.5em 0.5em -1em 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">RDF 1.1 Concepts and Abstract Syntax</h1><h2 property="dcterms:issued" datatype="xsd:dateTime" content="2011-08-29T23:00:00+0000" id="w3c-working-draft-30-august-2011">W3C Working Draft 30 August 2011</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2011/WD-rdf11-concepts-20110830/">http://www.w3.org/TR/2011/WD-rdf11-concepts-20110830/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/rdf11-concepts/">http://www.w3.org/TR/rdf11-concepts/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html">http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html</a></dd><dt>Latest recommendation:</dt><dd><a href="http://www.w3.org/TR/rdf-concepts/">http://www.w3.org/TR/rdf-concepts/</a></dd><dt>Editors:</dt><dd rel="bibo:editor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Richard Cyganiak" href="http://richard.cyganiak.de/">Richard Cyganiak</a>, <a rel="foaf:workplaceHomepage" href="http://www.deri.ie/">DERI, NUI Galway</a></span>
|
|
</dd>
|
|
<dd rel="bibo:editor"><span typeof="foaf:Person"><span property="foaf:name">David Wood</span>, <a rel="foaf:workplaceHomepage" href="http://www.talis.com/">Talis</a></span>
|
|
</dd>
|
|
<dt>Previous editors:</dt><dd><span><a content="Graham Klyne" href="http://www.ninebynine.org/">Graham Klyne</a>, Nine by Nine</span>
|
|
</dd>
|
|
<dd><span><span>Jeremy J. Carroll</span>, Hewlett Packard Labs</span>
|
|
</dd>
|
|
<dd><span><span>Brian McBride</span>, Hewlett Packard Labs (RDF 2004 Series Editor)</span>
|
|
</dd>
|
|
</dl><p class="copyright"><a rel="license" href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2004-2011 <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. W3C <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 Resource Description Framework (RDF) is a framework for
|
|
representing information in the Web.</p>
|
|
<p>RDF Concepts and Abstract Syntax defines an abstract syntax
|
|
on which RDF is based, and which serves to link its concrete
|
|
syntax to its formal semantics. It also includes discussion of
|
|
key concepts, datatyping, character normalization
|
|
and handling of IRIs.</p>
|
|
</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 W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p>
|
|
<p>This document is work in progress towards a revision of the
|
|
<a href="http://www.w3.org/TR/rdf-concepts/"><em>RDF Concepts
|
|
and Abstract Syntax</em></a> Recommendation,
|
|
and is intended to eventually replace that document.
|
|
It is part of a larger effort to revise the
|
|
<a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-Introduction">RDF specifications as published in 2004</a>.
|
|
The most significant changes from the 2004 edition are:
|
|
modified <a href="#section-Graph-Literal">string literals</a>,
|
|
a <a href="#section-skolemization">section on skolemization
|
|
of blank nodes</a>, and many updated
|
|
<a href="#references">references</a> to other specifications
|
|
(including a change in terminology from
|
|
“URI references” to “IRIs”). A fuller list of changes that
|
|
have been made to date is provided in <a href="#changes">Appendix A</a>.
|
|
Various areas of work to be tackled in upcoming
|
|
working drafts are highlighted throughout the document, but
|
|
should not yet be understood as an exhaustive list.</p>
|
|
<p>This document was published by the <a href="http://www.w3.org/2011/rdf-wg/">RDF Working Group</a> as a First Public Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to <a href="mailto:public-rdf-comments@w3.org">public-rdf-comments@w3.org</a> (<a href="mailto:public-rdf-comments-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-rdf-comments/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the W3C 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 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/46168/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 W3C 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="#section-Introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">2. </span>Conformance</a></li><li class="tocline"><a href="#section-Concepts" class="tocxref"><span class="secno">3. </span>RDF Concepts</a><ul class="toc"><li class="tocline"><a href="#section-data-model" class="tocxref"><span class="secno">3.1 </span>Graph Data Model</a></li><li class="tocline"><a href="#section-IRI-Vocabulary" class="tocxref"><span class="secno">3.2 </span>IRI-based Vocabulary and Node Identification</a></li><li class="tocline"><a href="#section-Datatypes-intro" class="tocxref"><span class="secno">3.3 </span>Datatypes</a></li><li class="tocline"><a href="#section-Literals" class="tocxref"><span class="secno">3.4 </span>Literals</a></li><li class="tocline"><a href="#section-Entailment" class="tocxref"><span class="secno">3.5 </span>Entailment</a></li></ul></li><li class="tocline"><a href="#section-URIspaces" class="tocxref"><span class="secno">4. </span>RDF Vocabulary IRI and Namespace</a></li><li class="tocline"><a href="#section-Datatypes" class="tocxref"><span class="secno">5. </span>Datatypes</a><ul class="toc"><li class="tocline"><a href="#section-XMLLiteral" class="tocxref"><span class="secno">5.1 </span>XML Content within an RDF Graph</a></li></ul></li><li class="tocline"><a href="#section-Graph-syntax" class="tocxref"><span class="secno">6. </span>Abstract Syntax</a><ul class="toc"><li class="tocline"><a href="#section-triples" class="tocxref"><span class="secno">6.1 </span>RDF Triples</a></li><li class="tocline"><a href="#section-rdf-graph" class="tocxref"><span class="secno">6.2 </span>RDF Graph</a></li><li class="tocline"><a href="#section-graph-equality" class="tocxref"><span class="secno">6.3 </span>Graph Equivalence</a></li><li class="tocline"><a href="#section-IRIs" class="tocxref"><span class="secno">6.4 </span>IRIs</a></li><li class="tocline"><a href="#section-Graph-Literal" class="tocxref"><span class="secno">6.5 </span>RDF Literals</a><ul class="toc"><li class="tocline"><a href="#section-Literal-Equality" class="tocxref"><span class="secno">6.5.1 </span>Literal Equality</a></li><li class="tocline"><a href="#section-Literal-Value" class="tocxref"><span class="secno">6.5.2 </span>The Value Corresponding to a Typed Literal</a></li></ul></li><li class="tocline"><a href="#section-blank-nodes" class="tocxref"><span class="secno">6.6 </span>Blank Nodes</a><ul class="toc"><li class="tocline"><a href="#section-skolemization" class="tocxref"><span class="secno">6.6.1 </span>Replacing Blank Nodes with IRIs</a></li></ul></li><li class="tocline"><a href="#section-multigraph" class="tocxref"><span class="secno">6.7 </span>Abstract Syntax for Working with Multiple Graphs</a></li></ul></li><li class="tocline"><a href="#section-fragID" class="tocxref"><span class="secno">7. </span>Fragment Identifiers</a></li><li class="tocline"><a href="#section-Acknowledgments" class="tocxref"><span class="secno">8. </span>Acknowledgments</a></li><li class="tocline"><a href="#changes" class="tocxref"><span class="secno">A. </span>Changes from RDF 2004</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">B. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">B.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">B.2 </span>Informative references</a></li></ul></li></ul></div>
|
|
|
|
|
|
|
|
|
|
|
|
<div id="section-Introduction" typeof="bibo:Chapter" about="#section-Introduction" class="section">
|
|
<!--OddPage--><h2><span class="secno">1. </span>Introduction</h2>
|
|
|
|
<p class="issue">This document reflects current progress of the RDF Working
|
|
Group towards updating the
|
|
<a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/">2004
|
|
version of <em>RDF Concepts and Abstract Syntax</em></a>. The
|
|
editors expect to work on a number of issues, some of which are
|
|
listed in boxes like this throughout the document.</p>
|
|
|
|
<p>The Resource Description Framework (RDF) is a framework for
|
|
representing information in the Web.</p>
|
|
|
|
<p>This document defines an abstract syntax (a data model)
|
|
on which RDF is based,
|
|
and which serves to link concrete syntaxes to its formal
|
|
semantics. It also includes discussion of
|
|
key concepts, datatyping, character normalization
|
|
and handling of IRIs.</p>
|
|
|
|
<p>Normative documentation of RDF falls into the following
|
|
areas:</p>
|
|
|
|
<ul>
|
|
<li>Serialization syntaxes (Turtle [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE-TR">TURTLE-TR</a></cite>], RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-PRIMER">RDFA-PRIMER</a></cite>], RDF/XML [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>], N-Triples [<cite><a class="bibref" rel="biblioentry" href="#bib-N-TRIPLES">N-TRIPLES</a></cite>]),</li>
|
|
|
|
<li>the RDF Vocabulary Description Language ([<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>]),</li>
|
|
|
|
<li>a formal model-theoretic semantics [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>], and</li>
|
|
|
|
<li>this document.</li>
|
|
</ul>
|
|
|
|
<p>The framework is designed so that vocabularies can be layered.
|
|
The terms defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>] are the first such vocabulary.
|
|
Several other vocabularies for RDF are
|
|
mentioned in the Primer [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-PRIMER">RDF-PRIMER</a></cite>].</p>
|
|
</div>
|
|
|
|
|
|
<div id="conformance" typeof="bibo:Chapter" about="#conformance" class="section"><!--OddPage--><h2><span class="secno">2. </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>
|
|
|
|
|
|
<div id="section-Concepts" class="informative section" typeof="bibo:Chapter" about="#section-Concepts">
|
|
<!--OddPage--><h2><span class="secno">3. </span>RDF Concepts</h2><p><em>This section is non-normative.</em></p>
|
|
|
|
<p class="issue">This section is quite redundant with later
|
|
normative sections and the RDF Primer. Its removal has been
|
|
proposed. This is
|
|
<a href="http://www.w3.org/2011/rdf-wg/track/issues/68">ISSUE-68</a>.</p>
|
|
|
|
<p>RDF uses the following key concepts:</p>
|
|
|
|
<ul>
|
|
<li>Graph data model</li>
|
|
|
|
<li>IRI-based vocabulary</li>
|
|
|
|
<li>Datatypes</li>
|
|
|
|
<li>Literals</li>
|
|
|
|
<li>Entailment</li>
|
|
</ul>
|
|
|
|
|
|
<div id="section-data-model" typeof="bibo:Chapter" about="#section-data-model" class="section">
|
|
<h3><span class="secno">3.1 </span>Graph Data Model</h3>
|
|
|
|
<p>The underlying structure of any expression in RDF is a
|
|
collection of triples, each consisting of a subject, a
|
|
predicate and an object. A set of such triples is called an RDF
|
|
graph (defined more formally in
|
|
<a href="#section-Graph-syntax">section 6</a>). This can be
|
|
illustrated by a node and directed-arc diagram, in which each
|
|
triple is represented as a node-arc-node link (hence the term
|
|
“graph”).</p>
|
|
|
|
<div class="figure">
|
|
<img src="Graph-ex.gif" alt="image of the RDF triple comprising (subject, predicate, object)">
|
|
</div>
|
|
|
|
<p>Each triple represents a statement of a relationship between
|
|
the things denoted by the nodes that it links. Each triple has
|
|
three parts:</p>
|
|
<ol>
|
|
<li>a <a href="#dfn-subject" class="internalDFN">subject</a>,</li>
|
|
<li>an <a href="#dfn-object" class="internalDFN">object</a>, and</li>
|
|
<li>a <a href="#dfn-predicate" class="internalDFN">predicate</a> (also called a
|
|
<a href="#dfn-property" class="internalDFN">property</a>) that denotes a
|
|
relationship.</li>
|
|
</ol>
|
|
<p>The direction of the arc is significant: it always points
|
|
toward the object.</p>
|
|
<p>The <a title="node" href="#dfn-node" class="internalDFN">nodes</a> of an RDF graph
|
|
are its subjects and objects.</p>
|
|
<p>The assertion of an RDF triple says that some relationship,
|
|
indicated by the predicate, holds between the things denoted by
|
|
subject and object of the triple. The assertion of an RDF graph
|
|
amounts to asserting all the triples in it, so the meaning of
|
|
an RDF graph is the conjunction (logical AND) of the statements
|
|
corresponding to all the triples it contains. A formal account
|
|
of the meaning of RDF graphs is given in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>].</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-IRI-Vocabulary" typeof="bibo:Chapter" about="#section-IRI-Vocabulary" class="section">
|
|
<h3><span class="secno">3.2 </span>IRI-based Vocabulary and Node Identification</h3>
|
|
|
|
<p>A <a href="#dfn-node" class="internalDFN">node</a> may be an <a href="#dfn-iri" class="internalDFN">IRI</a>, a <a href="#dfn-literal" class="internalDFN">literal</a>,
|
|
or <a title="blank node" href="#dfn-blank-node" class="internalDFN">blank</a> (having no separate form of identification).
|
|
Properties are <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>.</p>
|
|
<p>An <a href="#dfn-iri" class="internalDFN">IRI</a> or <a href="#dfn-literal" class="internalDFN">literal</a> used as a node identifies what
|
|
that node represents. An IRI used as a predicate
|
|
identifies a relationship between the things represented by the nodes it connects. A
|
|
predicate IRI may also be a node in the graph.</p>
|
|
<p>A <a href="#dfn-blank-node" class="internalDFN">blank node</a> is a node that is
|
|
not an IRI or a literal. In the RDF abstract syntax, a
|
|
blank node is just a unique node that can be used in one or
|
|
more RDF statements.</p>
|
|
<p>A convention used by some linear representations of an RDF
|
|
graph to allow several statements to use the same
|
|
blank node is to use a <dfn id="dfn-blank-node-identifier">blank node
|
|
identifier</dfn>, which is a local identifier that can be
|
|
distinguished from all IRIs and literals. When graphs are
|
|
merged, their blank nodes must be kept distinct if meaning is
|
|
to be preserved; this may call for re-allocation of blank node
|
|
identifiers. Note that such blank node identifiers are not part
|
|
of the RDF abstract syntax, and the representation of triples
|
|
containing blank nodes is entirely dependent on the particular
|
|
concrete syntax used.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-Datatypes-intro" typeof="bibo:Chapter" about="#section-Datatypes-intro" class="section">
|
|
<h3><span class="secno">3.3 </span>Datatypes</h3>
|
|
|
|
<p>Datatypes are used by RDF in the representation of values such
|
|
as integers, floating point numbers and dates.</p>
|
|
|
|
<p>
|
|
A datatype consists of a lexical space, a value space and a lexical-to-value
|
|
mapping, see <a href="#section-Datatypes">section 5</a>.
|
|
</p>
|
|
|
|
<p>For example, the lexical-to-value mapping for the XML Schema datatype
|
|
<var>xsd:boolean</var>, where each member of the value space
|
|
(represented here as 'T' and 'F') has two lexical representations,
|
|
is as follows:</p>
|
|
|
|
<table border="1" cellpadding="5" summary="A table detailing the xsd:boolean datatype.">
|
|
<tbody><tr>
|
|
<th align="left">Value Space</th>
|
|
|
|
<td>{T, F}</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<th align="left">Lexical Space</th>
|
|
|
|
<td>{"0", "1", "true", "false"}</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<th align="left">Lexical-to-Value Mapping</th>
|
|
|
|
<td>{<"true", T>, <"1", T>, <"0", F>,
|
|
<"false", F>}</td>
|
|
</tr>
|
|
</tbody></table>
|
|
|
|
<p>RDF predefines just one datatype <code><a href="#dfn-rdf-xmlliteral" class="internalDFN">rdf:XMLLiteral</a></code>, used for
|
|
embedding XML in RDF (see <a href="#section-XMLLiteral">section
|
|
5.1</a>).</p>
|
|
|
|
<p>There is no built-in concept of numbers or dates or other common
|
|
values. Rather, RDF defers to datatypes that are defined
|
|
separately, and identified with <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>.
|
|
The predefined XML Schema
|
|
datatypes [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>] are expected
|
|
to be widely used for this purpose.</p>
|
|
|
|
|
|
<p>RDF provides no mechanism for defining new datatypes. XML Schema
|
|
Datatypes [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>] provides an
|
|
extensibility framework suitable for defining new datatypes for use
|
|
in RDF.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-Literals" typeof="bibo:Chapter" about="#section-Literals" class="section">
|
|
<h3><span class="secno">3.4 </span>Literals</h3>
|
|
|
|
<p><a title="literal" href="#dfn-literal" class="internalDFN">Literals</a> are used to identify values such as numbers and dates
|
|
by means of a lexical representation. Anything represented by a
|
|
literal could also be represented by an <a href="#dfn-iri" class="internalDFN">IRI</a>, but it is often more
|
|
convenient or intuitive to use literals.</p>
|
|
|
|
<p>A literal may be the object of an RDF statement, but not the
|
|
subject or the predicate.</p>
|
|
|
|
<p>Literals may be <cite>typed</cite> or <cite>language-tagged</cite>:</p>
|
|
|
|
<ul>
|
|
<li>A <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> is a string combined with a
|
|
<a href="#dfn-datatype-iri" class="internalDFN">datatype IRI</a>. It denotes the
|
|
member of the identified datatype's value space obtained by
|
|
applying the lexical-to-value mapping to the literal string.</li>
|
|
|
|
<li>A <a href="#dfn-language-tagged-literal" class="internalDFN">language-tagged literal</a> is a string combined
|
|
with a language tag. This may be used for
|
|
plain text in a natural language. Language-tagged literals
|
|
are self-denoting.</li>
|
|
</ul>
|
|
|
|
<p>Continuing the example from <a href="#section-Datatypes-intro">section
|
|
3.3</a>, the typed literals that can be defined using the XML
|
|
Schema datatype <var>xsd:boolean</var> are:</p>
|
|
|
|
<table border="1" cellpadding="5" summary="This table lists the literals of type xsd:boolean.">
|
|
<tbody><tr>
|
|
<th>Typed Literal</th>
|
|
|
|
<th>Lexical-to-Value Mapping</th>
|
|
|
|
<th>Value</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><xsd:boolean, "true"></td>
|
|
|
|
<td align="center"><"true", T></td>
|
|
|
|
<td align="center">T</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><xsd:boolean, "1"></td>
|
|
|
|
<td align="center"><"1", T></td>
|
|
|
|
<td align="center">T</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><xsd:boolean, "false"></td>
|
|
|
|
<td align="center"><"false", F></td>
|
|
|
|
<td align="center">F</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><xsd:boolean, "0"></td>
|
|
|
|
<td align="center"><"0", F></td>
|
|
|
|
<td align="center">F</td>
|
|
</tr>
|
|
</tbody></table>
|
|
|
|
<p>For text that may contain
|
|
markup, use typed literals
|
|
with type <a href="#section-XMLLiteral">rdf:XMLLiteral</a>.
|
|
If language annotation is required,
|
|
it must be explicitly included as markup, usually by means of an
|
|
<code>xml:lang</code> attribute.
|
|
XHTML [<cite><a class="bibref" rel="biblioentry" href="#bib-XHTML10">XHTML10</a></cite>] may be included within RDF
|
|
in this way. Sometimes, in this latter case,
|
|
an additional <code>span</code> or <code>div</code>
|
|
element is needed to carry an
|
|
<code>xml:lang</code> or <code>lang</code> attribute.
|
|
</p>
|
|
|
|
<p class="issue">Update the XHTML 1.0 reference to something more recent?</p>
|
|
|
|
<p>
|
|
The string in both plain and typed literals is recommended to
|
|
be in Unicode Normal Form C [<cite><a class="bibref" rel="biblioentry" href="#bib-NFC">NFC</a></cite>]. This is motivated
|
|
by [<cite><a class="bibref" rel="biblioentry" href="#bib-CHARMOD">CHARMOD</a></cite>] particularly
|
|
<a href="http://www.w3.org/TR/2003/WD-charmod-20030822/#sec-Normalization">section 4
|
|
Early Uniform Normalization</a>.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-Entailment" typeof="bibo:Chapter" about="#section-Entailment" class="section">
|
|
<h3><span class="secno">3.5 </span>Entailment</h3>
|
|
|
|
<p>The ideas on meaning and inference in RDF are underpinned by the
|
|
formal concept of <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#entail">
|
|
<cite>entailment</cite></a>, as
|
|
discussed in the RDF
|
|
semantics document [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>].
|
|
In brief, an RDF expression A is said to
|
|
<dfn title="entailment" id="dfn-entailment">entail</dfn> another RDF expression B
|
|
if every possible
|
|
arrangement of things in the world that makes A true also makes B
|
|
true. On this basis, if the truth of A is presumed or demonstrated
|
|
then the truth of B can be inferred .
|
|
</p>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-URIspaces" typeof="bibo:Chapter" about="#section-URIspaces" class="section">
|
|
<!--OddPage--><h2><span class="secno">4. </span>RDF Vocabulary IRI and Namespace</h2>
|
|
|
|
<p>RDF uses <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a> to identify resources
|
|
and properties. Certain
|
|
IRIs with the following leading substring are defined by the
|
|
RDF specifications to denote specific concepts:</p>
|
|
|
|
<ul>
|
|
<li><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>
|
|
(conventionally associated with namespace prefix <code>rdf:</code>)</li>
|
|
</ul>
|
|
|
|
<p>Vocabulary terms in the <code>rdf:</code>
|
|
namespace are listed and described in detail in the
|
|
RDF Schema specification [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].</p>
|
|
|
|
<p class="note">The RDF namespace is also used as an
|
|
XML namespace [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-NAMES">XML-NAMES</a></cite>] to define a number of additional
|
|
element and attribute names for purely syntactic purposes within
|
|
the RDF/XML syntax ([<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>],
|
|
<a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#section-Namespace">section 5.1</a>).
|
|
These terms (e.g., <code>rdf:about</code> and <code>rdf:ID</code>)
|
|
do not denote concepts.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-Datatypes" typeof="bibo:Chapter" about="#section-Datatypes" class="section">
|
|
<!--OddPage--><h2><span class="secno">5. </span>Datatypes</h2>
|
|
|
|
<p class="issue">This section perhaps should discuss
|
|
<a href="http://www.w3.org/TR/rdf-mt/#dtype_interp">the XSD datatype map</a>
|
|
and <code><a href="http://www.w3.org/TR/rdf-plain-literal/">rdf:PlainLiteral</a></code>.
|
|
This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/70">ISSUE-70</a>.</p>
|
|
|
|
<p>
|
|
The datatype abstraction used in RDF is compatible with
|
|
the abstraction used in
|
|
XML Schema Part 2:
|
|
Datatypes [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-2">XMLSCHEMA-2</a></cite>].</p>
|
|
<p>
|
|
A datatype consists of a lexical space, a value space and a lexical-to-value
|
|
mapping.
|
|
</p>
|
|
<p>The <dfn id="dfn-lexical-space">lexical space</dfn> of a datatype is a set of Unicode [<cite><a class="bibref" rel="biblioentry" href="#bib-UNICODE">UNICODE</a></cite>] strings.</p>
|
|
<p>
|
|
The <dfn id="dfn-lexical-to-value-mapping">lexical-to-value mapping</dfn> of a datatype is a set of pairs whose
|
|
first element belongs to
|
|
the <a href="#dfn-lexical-space" class="internalDFN">lexical space</a> of the datatype,
|
|
and the second element belongs to the
|
|
<dfn id="dfn-value-space">value space</dfn> of the datatype:
|
|
</p>
|
|
<ul>
|
|
<li>
|
|
Each member of the lexical space is paired with (maps to) exactly one member
|
|
of the value space.
|
|
</li>
|
|
<li>
|
|
Each member of the value space may be paired with any number (including
|
|
zero) of members of the lexical space (lexical representations for that
|
|
value).
|
|
</li>
|
|
</ul>
|
|
<p>
|
|
A datatype is identified by one or more IRIs.
|
|
</p>
|
|
<p>
|
|
RDF may be used with any datatype definition that conforms to this
|
|
abstraction, even if not defined in terms of XML Schema.
|
|
</p>
|
|
<p>Certain XML Schema built-in datatypes are not suitable for use
|
|
within RDF. For example, the
|
|
<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#QName">QName</a>
|
|
datatype requires a namespace declaration to be in scope during
|
|
the mapping, and is not recommended for use in RDF.
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>] contains a
|
|
<a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#dtype_interp">more detailed discussion</a>
|
|
of specific XML Schema built-in datatypes. </p>
|
|
|
|
<div class="note">
|
|
<p>When the datatype is defined using XML Schema:
|
|
</p>
|
|
<ul>
|
|
<li>
|
|
All values correspond to some lexical form, either using
|
|
the lexical-to-value mapping of the datatype or if it is a union
|
|
datatype with a lexical mapping associated with one of the member
|
|
datatypes.
|
|
</li>
|
|
<li>
|
|
XML Schema facets remain part of the datatype and are used by the XML
|
|
Schema mechanisms that control the lexical space and the value space;
|
|
however, RDF does not define a standard mechanism to access these facets.</li>
|
|
|
|
<li>In [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLSCHEMA-1">XMLSCHEMA-1</a></cite>],
|
|
<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#section-White-Space-Normalization-during-Validation">
|
|
white space normalization</a> occurs
|
|
during
|
|
<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#key-vn">validation</a>
|
|
according to the value of the
|
|
<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#rf-whiteSpace">whiteSpace
|
|
facet</a>. The lexical-to-value mapping used in RDF datatyping
|
|
occurs after this, so that the whiteSpace facet has no
|
|
effect in RDF datatyping.
|
|
</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-XMLLiteral" typeof="bibo:Chapter" about="#section-XMLLiteral" class="section">
|
|
<h3><span class="secno">5.1 </span>XML Content within an RDF Graph</h3>
|
|
|
|
<p class="issue">The canonicalization rules required for XML literals
|
|
are quite complicated. Increasingly, RDF is produced and consumed in
|
|
environments where no XML parser and canonicalization engine is
|
|
available. A possible change to relax the requirements for the
|
|
lexical space, while retaining the value space, is under discussion.
|
|
This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/13">ISSUE-13</a>.</p>
|
|
|
|
<p>RDF provides for XML content as a possible literal value.
|
|
Such content is indicated in an RDF graph using a typed literal
|
|
whose datatype is a special built-in datatype
|
|
<dfn id="dfn-rdf-xmlliteral">rdf:XMLLiteral</dfn>,
|
|
defined as follows.</p>
|
|
|
|
|
|
<dl>
|
|
<dt><a name="XMLLiteral-uri" id="XMLLiteral-uri">An IRI for
|
|
identifying this datatype</a></dt>
|
|
|
|
<dd>is
|
|
<code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>.</dd>
|
|
|
|
|
|
|
|
|
|
<dt><a name="XMLLiteral-lexical-space" id="XMLLiteral-lexical-space">The lexical space</a></dt>
|
|
|
|
<dd>is the set of all
|
|
strings:
|
|
<ul>
|
|
<li>which are well-balanced, self-contained
|
|
<a href="http://www.w3.org/TR/2000/REC-xml-20001006#NT-content">
|
|
XML content</a>
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-XML10">XML10</a></cite>];
|
|
</li>
|
|
<li>for which encoding as UTF-8
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-UTF-8">UTF-8</a></cite>] yields
|
|
<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-exclusive-canonical-XML">
|
|
exclusive
|
|
Canonical XML </a> (with comments, with empty
|
|
<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-InclusiveNamespaces-PrefixList">
|
|
InclusiveNamespaces PrefixList
|
|
</a>) [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-EXC-C14N">XML-EXC-C14N</a></cite>];
|
|
</li>
|
|
<li>for which embedding between an arbitrary XML start tag and an end tag
|
|
yields a document conforming to <a href="http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
|
|
Namespaces</a> [<cite><a class="bibref" rel="biblioentry" href="#bib-XML-NAMES">XML-NAMES</a></cite>]</li>
|
|
</ul>
|
|
</dd>
|
|
|
|
|
|
<dt><a name="XMLLiteral-value-space" id="XMLLiteral-value-space">The value space</a></dt>
|
|
|
|
<dd>is a set of entities, called XML values, which is:
|
|
<ul>
|
|
<li>disjoint from the lexical space;</li>
|
|
<li>disjoint from the value space of any other datatype that is not explicitly defined as a sub- or supertype of this datatype;</li>
|
|
<li>disjoint from the set of Unicode character strings [<cite><a class="bibref" rel="biblioentry" href="#bib-UNICODE">UNICODE</a></cite>];</li>
|
|
<li>and in 1:1 correspondence with the lexical space.</li>
|
|
</ul>
|
|
</dd>
|
|
|
|
<dt><a name="XMLLiteral-mapping" id="XMLLiteral-mapping">The lexical-to-value mapping</a></dt>
|
|
|
|
<dd>
|
|
is a one-one mapping from the lexical space onto the value space,
|
|
i.e. it is both injective and surjective.
|
|
</dd>
|
|
|
|
|
|
|
|
</dl>
|
|
|
|
<p class="note">Not all values of this datatype are compliant
|
|
with XML 1.1 [<cite><a class="bibref" rel="biblioentry" href="#bib-XML11">XML11</a></cite>]. If compliance
|
|
with XML 1.1 is desired, then only those values that are
|
|
<a href="http://www.w3.org/TR/2002/CR-xml11-20021015/#sec2.13">fully
|
|
normalized</a> according to XML 1.1 should be used.</p>
|
|
|
|
<p class="note">XML values can be thought of as the
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-XML-INFOSET">XML-INFOSET</a></cite>] or the [<cite><a class="bibref" rel="biblioentry" href="#bib-XPATH">XPATH</a></cite>]
|
|
nodeset corresponding to the lexical form, with an appropriate equality
|
|
function.</p>
|
|
|
|
<p class="note">RDF applications may use additional equivalence relations, such as
|
|
that which relates an
|
|
<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#string"><code>xsd:string</code></a>
|
|
|
|
with an <code>rdf:XMLLiteral</code> corresponding to
|
|
a single text node of the same string.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-Graph-syntax" typeof="bibo:Chapter" about="#section-Graph-syntax" class="section">
|
|
<!--OddPage--><h2><span class="secno">6. </span>Abstract Syntax</h2>
|
|
|
|
<p>This section defines the RDF abstract syntax. The RDF abstract
|
|
syntax is a set of triples, called the RDF graph.</p>
|
|
|
|
<p>This section also defines equivalence between RDF graphs. A
|
|
definition of equivalence is needed to support the RDF Test Cases
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-TESTCASES">RDF-TESTCASES</a></cite>] specification.</p>
|
|
|
|
<p class="note">This <em>abstract</em> syntax is the
|
|
syntax over which the formal semantics are defined.
|
|
Implementations are free to represent RDF graphs in
|
|
any other equivalent form. As an example:
|
|
in an RDF graph,
|
|
literals with datatype <tt>rdf:XMLLiteral</tt> can be represented
|
|
in a non-canonical
|
|
format, and canonicalization performed during the comparison between two
|
|
such literals. In this example the comparisons may be
|
|
being performed either between syntactic structures or
|
|
between their denotations in the domain of discourse.
|
|
Implementations that do not require any such comparisons can
|
|
hence be optimized.
|
|
</p>
|
|
|
|
|
|
<div id="section-triples" typeof="bibo:Chapter" about="#section-triples" class="section">
|
|
<h3><span class="secno">6.1 </span>RDF Triples</h3>
|
|
|
|
<p>An <dfn id="dfn-rdf-triple">RDF triple</dfn> contains three components:</p>
|
|
|
|
<ul>
|
|
<li>the <dfn id="dfn-subject">subject</dfn>, which is an
|
|
<a href="#dfn-iri" class="internalDFN">IRI</a> or a <a href="#dfn-blank-node" class="internalDFN">blank node</a></li>
|
|
|
|
<li>the <dfn id="dfn-predicate">predicate</dfn>, which is an <a href="#dfn-iri" class="internalDFN">IRI</a></li>
|
|
|
|
<li>the <dfn id="dfn-object">object</dfn>, which is an <a href="#dfn-iri" class="internalDFN">IRI</a>,
|
|
a <a href="#dfn-literal" class="internalDFN">literal</a> or a <a href="#dfn-blank-node" class="internalDFN">blank node</a></li>
|
|
</ul>
|
|
|
|
<p>An RDF triple is conventionally written in the order subject,
|
|
predicate, object.</p>
|
|
|
|
<p>The predicate is also known as the <dfn id="dfn-property">property</dfn> of the triple.</p>
|
|
|
|
<p><a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>, <a title="blank node" href="#dfn-blank-node" class="internalDFN">blank nodes</a> and
|
|
<a title="literal" href="#dfn-literal" class="internalDFN">literals</a> are collectively known as
|
|
<dfn title="RDF term" id="dfn-rdf-term">RDF terms</dfn>.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-rdf-graph" typeof="bibo:Chapter" about="#section-rdf-graph" class="section">
|
|
<h3><span class="secno">6.2 </span>RDF Graph</h3>
|
|
|
|
<p>An <dfn id="dfn-rdf-graph">RDF graph</dfn> is a set of RDF triples.</p>
|
|
|
|
<p>The set of <dfn title="node" id="dfn-node">nodes</dfn> of an RDF graph is the set of subjects and objects of
|
|
triples in the graph.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-graph-equality" typeof="bibo:Chapter" about="#section-graph-equality" class="section">
|
|
<h3><span class="secno">6.3 </span>Graph Equivalence</h3>
|
|
|
|
<p>Two <a title="RDF graph" href="#dfn-rdf-graph" class="internalDFN">RDF graphs</a> <var>G</var> and <var>G'</var> are equivalent if there
|
|
is a bijection <var>M</var> between the sets of nodes of the two graphs,
|
|
such that:</p>
|
|
|
|
<ol>
|
|
<li><var>M</var> maps blank nodes to blank nodes.</li>
|
|
<li><var>M(lit)=lit</var> for all <a title="literal" href="#dfn-literal" class="internalDFN">RDF literals</a> <var>lit</var> which
|
|
are nodes of <var>G</var>.</li>
|
|
|
|
<li><var>M(uri)=uri</var> for all <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a> <var>uri</var>
|
|
which are nodes of <var>G</var>.</li>
|
|
|
|
<li>The triple <var>( s, p, o )</var> is in <var>G</var> if and
|
|
only if the triple <var>( M(s), p, M(o) )</var> is in
|
|
<var>G'</var></li>
|
|
</ol>
|
|
<p>With this definition, <var>M</var> shows how each blank node
|
|
in <var>G</var> can be replaced with
|
|
a new blank node to give <var>G'</var>.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-IRIs" typeof="bibo:Chapter" about="#section-IRIs" class="section">
|
|
<h3><span class="secno">6.4 </span>IRIs</h3>
|
|
|
|
<p>An <dfn title="IRI" id="dfn-iri"><acronym title="Internationalized Resource Identifier">IRI</acronym></dfn>
|
|
(Internationalized Resource Identifier) within an RDF graph
|
|
is a Unicode string [<cite><a class="bibref" rel="biblioentry" href="#bib-UNICODE">UNICODE</a></cite>] that conforms to the syntax
|
|
defined in RFC 3987 [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>]. IRIs are a generalization of
|
|
<dfn title="URI" id="dfn-uri"><acronym title="Uniform Resource Identifier">URI</acronym>s</dfn>
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-URI">URI</a></cite>]. Every absolute URI and URL is an IRI.</p>
|
|
|
|
<p>IRIs in the RDF abstract syntax <em class="rfc2119" title="must">must</em> be absolute, and <em class="rfc2119" title="may">may</em>
|
|
contain a fragment identifier.</p>
|
|
|
|
<p>Two IRIs are equal if and only if they are equivalent
|
|
under Simple String Comparison according to
|
|
<a href="http://tools.ietf.org/html/rfc3987#section-5.1">section 5.1</a>
|
|
of [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>]. Further normalization <em class="rfc2119" title="must not">must not</em> be performed when
|
|
comparing IRIs for equality.</p>
|
|
|
|
<p class="note">When IRIs are used in operations that are only
|
|
defined for URIs, they must first be converted according to
|
|
the mapping defined in
|
|
<a href="http://tools.ietf.org/html/rfc3987#section-3.1">section 3.1</a>
|
|
of [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>]. A notable example is retrieval over the HTTP
|
|
protocol. The mapping involves UTF-8 encoding of non-ASCII
|
|
characters, %-encoding of octets not allowed in URIs, and
|
|
Punycode-encoding of domain names.</p>
|
|
|
|
<p class="note">Some concrete syntaxes permit relative IRIs
|
|
as a shorthand for absolute IRIs, and define how to resolve
|
|
the relative IRIs against a base IRI.</p>
|
|
|
|
<p class="note">Previous versions of RDF used the term
|
|
“<dfn id="dfn-rdf-uri-reference">RDF URI Reference</dfn>” instead of “IRI” and allowed
|
|
additional characters:
|
|
“<code><</code>”, “<code>></code>”,
|
|
“<code>{</code>”, “<code>}</code>”,
|
|
“<code>|</code>”, “<code>\</code>”,
|
|
“<code>^</code>”, “<code>`</code>”,
|
|
‘<code>“</code>’ (double quote), and “<code> </code>” (space).
|
|
In IRIs, these characters must be percent-encoded as
|
|
described in <a href="http://tools.ietf.org/html/rfc3986#section-2.1">section 2.1</a>
|
|
of [<cite><a class="bibref" rel="biblioentry" href="#bib-URI">URI</a></cite>].</p>
|
|
|
|
<div class="note">
|
|
<p>Interoperability problems can be avoided by minting
|
|
only IRIs that are normalized according to
|
|
<a href="http://tools.ietf.org/html/rfc3987#section-5">Section 5</a>
|
|
of [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>]. Non-normalized forms that should be avoided
|
|
include:</p>
|
|
|
|
<ul>
|
|
<li>Uppercase characters in scheme names and domain names</li>
|
|
<li>Percent-encoding of characters where it is not
|
|
required by IRI syntax</li>
|
|
<li>Explicitly stated HTTP default port
|
|
(<code>http://example.com:80/</code>);
|
|
<code>http://example.com/</code> is preferrable</li>
|
|
<li>Completely empty path in HTTP IRIs
|
|
(<code>http://example.com</code>);
|
|
<code>http://example.com/</code> is preferrable</li>
|
|
<li>“<code>/./</code>” or “<code>/../</code>” in the path
|
|
component of an IRI</li>
|
|
<li>Lowercase hexadecimal letters within percent-encoding
|
|
triplets (“<code>%3F</code>” is preferable over
|
|
“<code>%3f</code>”)</li>
|
|
<li>Punycode-encoding of Internationalized Domain Names
|
|
in IRIs</li>
|
|
<li>IRIs that are not in Unicode Normalization
|
|
Form C [<cite><a class="bibref" rel="biblioentry" href="#bib-NFC">NFC</a></cite>]</li>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
<div id="section-Graph-Literal" typeof="bibo:Chapter" about="#section-Graph-Literal" class="section">
|
|
<h3><span class="secno">6.5 </span>RDF Literals</h3>
|
|
|
|
<p class="issue">This section is a major departure from RDF 2004
|
|
as <a title="simple literal" href="#dfn-simple-literal" class="internalDFN">simple literals</a> are now treated
|
|
as syntactic sugar for <code>xsd:string</code>
|
|
<a title="typed literal" href="#dfn-typed-literal" class="internalDFN">typed literals</a>. Further changes
|
|
to RDF's literal design are under consideration:
|
|
<a title="language-tagged literal" href="#dfn-language-tagged-literal" class="internalDFN">Language-tagged literals</a>
|
|
may receive a datatype, and
|
|
<a href="http://www.w3.org/TR/rdf-plain-literal/"><code>rdf:PlainLiteral</code>s</a> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-PLAINLITERAL">RDF-PLAINLITERAL</a></cite>]
|
|
may be folded into the design somehow. This is
|
|
<a href="http://www.w3.org/2011/rdf-wg/track/issues/71">ISSUE-71</a>.</p>
|
|
|
|
<p>A <dfn id="dfn-literal">literal</dfn> in an <a href="#dfn-rdf-graph" class="internalDFN">RDF graph</a> is either a
|
|
<a href="#dfn-typed-literal" class="internalDFN">typed literal</a> or a <a href="#dfn-language-tagged-literal" class="internalDFN">language-tagged literal</a>.</p>
|
|
|
|
<p>All literals have a <dfn id="dfn-lexical-form">lexical form</dfn> being a Unicode
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-UNICODE">UNICODE</a></cite>] string, which <em class="rfc2119" title="should">should</em> be in Normal Form C [<cite><a class="bibref" rel="biblioentry" href="#bib-NFC">NFC</a></cite>].</p>
|
|
|
|
<p><dfn title="language-tagged literal" id="dfn-language-tagged-literal">Language-tagged literals</dfn> have
|
|
a <a href="#dfn-lexical-form" class="internalDFN">lexical form</a> and a non-empty <dfn id="dfn-language-tag">language tag</dfn> as
|
|
defined by [<cite><a class="bibref" rel="biblioentry" href="#bib-BCP47">BCP47</a></cite>]. The language tag <em class="rfc2119" title="must">must</em> be well-formed according to
|
|
<a href="http://tools.ietf.org/html/bcp47#section-2.2.9">section 2.2.9</a>
|
|
of [<cite><a class="bibref" rel="biblioentry" href="#bib-BCP47">BCP47</a></cite>], and <em class="rfc2119" title="must">must</em> be normalized to lowercase.</p>
|
|
|
|
<p><dfn title="typed literal" id="dfn-typed-literal">Typed literals</dfn> have a <a href="#dfn-lexical-form" class="internalDFN">lexical form</a>
|
|
and a <dfn id="dfn-datatype-iri">datatype IRI</dfn> being an <a href="#dfn-iri" class="internalDFN">IRI</a>.</p>
|
|
|
|
<p>Concrete syntaxes <em class="rfc2119" title="may">may</em> support <dfn title="simple literal" id="dfn-simple-literal">simple
|
|
literals</dfn>, consisting of only a <a href="#dfn-lexical-form" class="internalDFN">lexical form</a>
|
|
without any language tag or datatype IRI. Simple literals only
|
|
exist in concrete syntaxes, and are treated as
|
|
syntactic sugar for abstract syntax
|
|
<a title="plain literal" href="#dfn-plain-literal" class="internalDFN">typed literals</a> with the datatype IRI
|
|
<code>http://www.w3.org/2001/XMLSchema#string</code>.
|
|
Simple literals and <a>language-tagged literals</a> are
|
|
collectively known as <dfn title="plain literal" id="dfn-plain-literal">plain literals</dfn>.</p>
|
|
|
|
<p class="note">Earlier versions of RDF allowed
|
|
<a title="simple literal" href="#dfn-simple-literal" class="internalDFN">simple literals</a> in the abstract syntax.</p>
|
|
|
|
<p class="note">Literals in which the lexical form begins with a
|
|
composing character (as defined by [<cite><a class="bibref" rel="biblioentry" href="#bib-CHARMOD">CHARMOD</a></cite>]) are allowed however they may cause
|
|
interoperability problems, particularly with XML version 1.1 [<cite><a class="bibref" rel="biblioentry" href="#bib-XML11">XML11</a></cite>].</p>
|
|
|
|
<p class="note">Earlier versions of RDF permitted tags that
|
|
adhered to the generic tag/subtag syntax of language tags,
|
|
but were not well-formed according to [<cite><a class="bibref" rel="biblioentry" href="#bib-BCP47">BCP47</a></cite>]. Such
|
|
language tags do not conform to RDF 1.1.</p>
|
|
|
|
<p class="note">When using the language tag, care must be
|
|
taken not to confuse language with locale. The language
|
|
tag relates only to human language text. Presentational
|
|
issues should
|
|
be addressed in end-user applications.</p>
|
|
|
|
<p class="note">The case normalization of
|
|
language tags is part of
|
|
the description of the abstract syntax, and consequently the abstract
|
|
behaviour of RDF applications. It does not constrain an
|
|
RDF implementation to actually normalize the case. Crucially, the result
|
|
of comparing two language tags should not be sensitive to the case of
|
|
the original input.</p>
|
|
|
|
|
|
<div id="section-Literal-Equality" typeof="bibo:Chapter" about="#section-Literal-Equality" class="section">
|
|
<h4><span class="secno">6.5.1 </span>Literal Equality</h4>
|
|
|
|
<p>Two literals are equal if and only if all of the following
|
|
hold:</p>
|
|
|
|
<ul>
|
|
<li>The strings of the two lexical forms compare equal, character
|
|
by character.</li>
|
|
|
|
<li>Either both or neither have language tags.</li>
|
|
|
|
<li>The language tags, if any, compare
|
|
equal.</li>
|
|
|
|
<li>Either both or neither have datatype IRIs.</li>
|
|
|
|
<li>The two datatype IRIs, if any, compare equal, character by
|
|
character.</li>
|
|
</ul>
|
|
|
|
<p class="note">RDF Literals are distinct and distinguishable
|
|
from <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>; e.g. <code>http://example.org/</code> as an RDF
|
|
Literal (untyped, without a language tag) is not equal to
|
|
<code>http://example.org/</code> as an IRI.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-Literal-Value" typeof="bibo:Chapter" about="#section-Literal-Value" class="section">
|
|
<h4><span class="secno">6.5.2 </span>The Value Corresponding to a Typed Literal</h4>
|
|
|
|
<p>The datatype IRI refers to a <a href="#section-Datatypes">datatype</a>. For XML Schema <a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#built-in-datatypes">
|
|
built-in</a> datatypes, IRIs such as
|
|
<code>http://www.w3.org/2001/XMLSchema#int</code> are used. The IRI
|
|
of the datatype <a href="#section-XMLLiteral"><tt>rdf:XMLLiteral</tt></a> may be used.
|
|
There may be other, implementation dependent, mechanisms by which
|
|
IRIs refer to datatypes.</p>
|
|
|
|
<p>The <em>value</em> associated with a typed literal is found by
|
|
applying the lexical-to-value mapping associated with the datatype IRI to
|
|
the lexical form.
|
|
</p>
|
|
|
|
<p>
|
|
If the lexical form is not in
|
|
the lexical space of the datatype associated with the datatype IRI,
|
|
then no literal value can be associated with the typed literal.
|
|
Such a case, while in error, is not <em>syntactically</em> ill-formed.</p>
|
|
<!--
|
|
<p>A typed literal for which the datatype does not map the lexical
|
|
form to a value is not syntactically ill-formed.</p>
|
|
-->
|
|
|
|
|
|
<p class="note">
|
|
In application contexts, comparing the values of typed literals (see
|
|
<a href="#section-Literal-Value">
|
|
section
|
|
6.5.2</a>)
|
|
is usually more helpful than comparing their syntactic forms (see
|
|
<a href="#section-Literal-Equality">
|
|
section
|
|
6.5.1</a>).
|
|
Similarly, for comparing RDF Graphs,
|
|
semantic notions of entailment (see
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MT">RDF-MT</a></cite>]) are usually
|
|
more helpful than syntactic equality (see
|
|
<a href="#section-graph-equality">
|
|
section
|
|
6.3</a>).</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-blank-nodes" typeof="bibo:Chapter" about="#section-blank-nodes" class="section">
|
|
<h3><span class="secno">6.6 </span>Blank Nodes</h3>
|
|
|
|
<p>
|
|
The <dfn title="blank node" id="dfn-blank-node">blank nodes</dfn> in an RDF graph
|
|
are drawn from an infinite set.
|
|
This set of blank nodes, the set of all <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>
|
|
and the set of all <a title="literal" href="#dfn-literal" class="internalDFN">literals</a> are pairwise disjoint.
|
|
</p>
|
|
<p>
|
|
Otherwise, this set of blank nodes is arbitrary.
|
|
</p>
|
|
<p>RDF makes no reference to any internal structure of blank nodes.
|
|
Given two blank nodes, it is
|
|
possible to determine whether or not they are the same.</p>
|
|
|
|
|
|
<div id="section-skolemization" typeof="bibo:Chapter" about="#section-skolemization" class="section">
|
|
<h4><span class="secno">6.6.1 </span>Replacing Blank Nodes with IRIs</h4>
|
|
|
|
<p>Blank nodes do not have identifiers in the RDF abstract syntax. The
|
|
<a title="blank node identifier" href="#dfn-blank-node-identifier" class="internalDFN">blank node identifiers</a> introduced
|
|
by some concrete syntaxes have only
|
|
local scope and are purely an artifact of the serialization.</p>
|
|
|
|
<p>In situations where stronger identification is needed, systems <em class="rfc2119" title="may">may</em>
|
|
systematically transform some or all of the blank nodes in an RDF graph
|
|
into IRIs [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>]. Systems wishing to do this <em class="rfc2119" title="should">should</em> mint a new, globally
|
|
unique IRI (a <dfn id="dfn-skolem-iri">Skolem IRI</dfn>) for each blank node so transformed.</p>
|
|
|
|
<p>This transformation does not change the meaning of an RDF graph,
|
|
provided that the Skolem IRIs do not occur anywhere else.</p>
|
|
|
|
<p>Systems may wish to mint Skolem IRIs in such a way that they can
|
|
recognize the IRIs as having been introduced solely to replace a blank
|
|
node, and map back to the source blank node where possible.</p>
|
|
|
|
<p>Systems that want Skolem IRIs to be recognizable outside of the system
|
|
boundaries <em class="rfc2119" title="should">should</em> use a well-known IRI [<cite><a class="bibref" rel="biblioentry" href="#bib-WELL-KNOWN">WELL-KNOWN</a></cite>] with the registered
|
|
name <code>genid</code>. This is an IRI that uses the HTTP or HTTPS scheme,
|
|
or another scheme that has been specified to use well-known IRIs; and whose
|
|
path component starts with <code>/.well-known/genid/</code>.
|
|
|
|
</p><p>For example, the authority responsible for the domain
|
|
<code>example.com</code> could mint the following recognizable Skolem IRI:</p>
|
|
|
|
<pre>http://example.com/.well-known/genid/d26a2d0e98334696f4ad70a677abc1f6</pre>
|
|
|
|
<p class="issue">IETF registration of the <code>genid</code> name is
|
|
currently in progress.</p>
|
|
|
|
<p class="note">RFC 5785 [<cite><a class="bibref" rel="biblioentry" href="#bib-WELL-KNOWN">WELL-KNOWN</a></cite>] only specifies well-known URIs,
|
|
not IRIs. For the purpose of this document, a well-known IRI is any
|
|
IRI that results in a well-known URI after IRI-to-URI mapping [<cite><a class="bibref" rel="biblioentry" href="#bib-IRI">IRI</a></cite>].</p>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-multigraph" typeof="bibo:Chapter" about="#section-multigraph" class="section">
|
|
<h3><span class="secno">6.7 </span>Abstract Syntax for Working with Multiple Graphs</h3>
|
|
|
|
<div class="issue">
|
|
<p>The Working Group will standardize a model and semantics for
|
|
multiple graphs and graphs stores. The
|
|
<a href="http://www.w3.org/2011/01/rdf-wg-charter">charter</a> notes:</p>
|
|
|
|
<blockquote>The RDF Community has used the
|
|
term “named graphs” for a number of years in various settings,
|
|
but this term is ambiguous, and often refers to what could rather
|
|
be referred as quoted graphs, graph literals, IRIs for graphs,
|
|
knowledge bases, graph stores, etc. The term “Support for Multiple
|
|
Graphs and Graph Stores” is used as a neutral term in this charter;
|
|
this term is not and should not be considered as definitive.
|
|
The Working Group will have to define the right term(s).</blockquote>
|
|
|
|
<p>Progress on the design for this feature is tracked under multiple
|
|
issues:</p>
|
|
|
|
<ul>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/5">ISSUE-5: Should we define Graph Literal datatypes?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/14">ISSUE-14: What is a named graph and what should we call it?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/15">ISSUE-15: What is the relationship between the IRI and the triples in a dataset/quad-syntax/etc</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/17">ISSUE-17: How are RDF datasets to be merged?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/22">ISSUE-22: Does multigraph syntax need to support empty graphs?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/28">ISSUE-28: Do we need syntactic nesting of graphs (g-texts) as in N3?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/29">ISSUE-29: Do we support SPARQL's notion of "default graph"?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/30">ISSUE-30: How does SPARQL's notion of RDF dataset relate our notion of multiple graphs?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/32">ISSUE-32: Can we identify both g-boxes and g-snaps?</a></li>
|
|
<li><a href="http://www.w3.org/2011/rdf-wg/track/issues/33">ISSUE-33: Do we provide a way to refer to sub-graphs and/or individual triples?</a></li>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div id="section-fragID" class="informative section" typeof="bibo:Chapter" about="#section-fragID">
|
|
<!--OddPage--><h2><span class="secno">7. </span>Fragment Identifiers</h2><p><em>This section is non-normative.</em></p>
|
|
|
|
<p class="issue">This section does not address the case where RDF is
|
|
embedded in other document formats, such as in RDFa or when an RDF/XML
|
|
fragment is embedded in SVG. It has been suggested that this may be
|
|
a general issue for the TAG about the treatment of
|
|
fragment identifiers when one language is embedded in another. This is
|
|
<a href="http://www.w3.org/2011/rdf-wg/track/issues/37">ISSUE-37</a>.</p>
|
|
|
|
<p class="issue">This section treats the RDF/XML media type as
|
|
canonical for establishing the referent of IRIs that include
|
|
fragment identifier. Today we have many different media types
|
|
that can carry RDF graphs, and HTTP content negotiation is more
|
|
common. Also, the problem addressed in the section
|
|
(context-dependence of fragment identifiers) has to some extent
|
|
gone away when RFC 2396 was replaced by RFC 3986. The latter
|
|
states that the same fragment should be used for the same thing
|
|
in resources that have multiple representations
|
|
(Section 3.5 [<cite><a class="bibref" rel="biblioentry" href="#bib-URI">URI</a></cite>]). This is
|
|
<a href="http://www.w3.org/2011/rdf-wg/track/issues/69">ISSUE-69</a>.</p>
|
|
|
|
<p>RDF uses <a title="IRI" href="#dfn-iri" class="internalDFN">IRIs</a>,
|
|
which may include fragment identifiers, as
|
|
context free identifiers for resources. RFC 2396 states
|
|
that the meaning of a fragment
|
|
identifier depends on the MIME content-type of a document, i.e.
|
|
is context dependent.</p>
|
|
<p>These apparently conflicting views are reconciled by
|
|
considering that an <a href="#dfn-iri" class="internalDFN">IRI</a> in an RDF graph is treated
|
|
with respect to the MIME type <code>application/rdf+xml</code>
|
|
[<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-MIME-TYPE">RDF-MIME-TYPE</a></cite>]. Given an IRI that includes a fragment identifier,
|
|
the fragment identifer identifies the same thing
|
|
that it does in an <code>application/rdf+xml</code> representation of the
|
|
resource identified by the IRI excluding the fragment identifier. Thus:</p>
|
|
<ul>
|
|
<li>we assume that the IRI excluding fragment
|
|
identifier identifies a resource, which is presumed to have
|
|
an RDF representation. So when <code>eg:someurl#frag</code> is used in an RDF
|
|
document, <code>eg:someurl</code> is taken to
|
|
designate some RDF document (even when no such document can
|
|
be retrieved).</li>
|
|
<li><code>eg:someurl#frag</code> means the thing
|
|
that is indicated, according to the rules of the
|
|
<code>application/rdf+xml</code> MIME content-type as
|
|
a “fragment” or “view” of the RDF document at
|
|
<code>eg:someurl</code>. If the document does not
|
|
exist, or cannot be retrieved, or is available only in
|
|
formats other than <code>application/rdf+xml</code>, then exactly what
|
|
that view may be is somewhat undetermined, but that does not
|
|
prevent use of RDF to say things about it.</li>
|
|
<li>the RDF treatment of a fragment identifier allows it to
|
|
indicate a thing that is entirely external to the document,
|
|
or even to the “shared information space” known as the Web.
|
|
That is, it can be a more general idea, like some particular
|
|
car or a mythical Unicorn.</li>
|
|
<li>in this way, an <code>application/rdf+xml</code> document acts as an
|
|
intermediary between some Web retrievable documents (itself,
|
|
at least, also any other Web retrievable IRIs that it may
|
|
use, possibly including schema IRIs and references to other
|
|
RDF documents), and some set of possibly abstract or non-Web
|
|
entities that the RDF may describe.</li>
|
|
</ul>
|
|
<p>This provides a handling of IRIs and their
|
|
denotation that is consistent with the RDF model theory and
|
|
usage, and also with conventional Web behavior. Note that
|
|
nothing here requires that an RDF application be able to
|
|
retrieve any representation of resources identified by the IRIs
|
|
in an RDF graph.</p>
|
|
</div>
|
|
|
|
|
|
<div id="section-Acknowledgments" class="informative section" typeof="bibo:Chapter" about="#section-Acknowledgments">
|
|
<!--OddPage--><h2><span class="secno">8. </span>Acknowledgments</h2><p><em>This section is non-normative.</em></p>
|
|
|
|
<p class="issue">This section does not yet list those who made
|
|
contributions to the RDF 1.1 version, nor does it list the
|
|
current RDF WG members.</p>
|
|
|
|
<p>The RDF 2004 editors acknowledge valuable contributions from
|
|
Frank Manola, Pat Hayes, Dan Brickley, Jos de Roo,
|
|
Dave Beckett, Patrick Stickler, Peter F. Patel-Schneider, Jerome Euzenat,
|
|
Massimo Marchiori, Tim Berners-Lee, Dave Reynolds and Dan Connolly.</p>
|
|
|
|
<p>This specification contains a significant contribution from the
|
|
designers of the RDF typed literal mechanism, Pat
|
|
Hayes, Sergey Melnik and Patrick Stickler. The document draws upon an earlier
|
|
RDF Model and Syntax document edited by Ora Lassilla and Ralph Swick,
|
|
and RDF Schema edited by Dan Brickley and R. V. Guha.</p>
|
|
|
|
<p>This specification is a product of extended deliberations by the
|
|
<a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-Acknowledgments">members
|
|
of the RDFcore Working Group and the RDF and RDF Schema Working Group</a>.</p>
|
|
</div>
|
|
|
|
|
|
<div class="appendix informative section" id="changes" typeof="bibo:Chapter" about="#changes">
|
|
<!--OddPage--><h2><span class="secno">A. </span>Changes from RDF 2004</h2><p><em>This section is non-normative.</em></p>
|
|
|
|
<ul>
|
|
<li>2011-08-13: Updated Turtle reference to Turtle FPWD</li>
|
|
<li>2011-07-21: Condensed the 2004 acknowledgements</li>
|
|
<li>2011-07-21: Updated the two sections on literals to reflect the <a href="">ISSUE-12 resolution</a> that simple literals are no longer part of the abstract syntax. Formally introduced the terms “language-tagged literal”, “simple literal”.</li>
|
|
<li>2011-07-21: Updated the introduction, and removed many mentions of RDF/XML. Changed the normative reference for the terms in the RDF namespace from the RDF/XML spec to the RDF Schema spec. Removed any mention of the 1999 version of RDF.</li>
|
|
<li>2011-07-21: Replaced RFC 2279 reference (UTF-8) with RFC 3629</li>
|
|
<li>2011-07-20: Removed informative sections “Motivations and Goals” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-Overview">RDF 2004 version</a>) and “RDF Expression of Simple Facts” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-SimpleFacts">RDF 2004 version</a>)</li>
|
|
<li>2011-06-01: Replaced the URI References section with <a href="#section-IRIs">new section on IRIs</a>, and changed “RDF URI Reference” to “IRI” throughout the document.</li>
|
|
<li>2011-06-01: Changed language tag definition to require well-formedness according to BCP47; added a note that this invalidates some RDF</li>
|
|
<li>2011-05-25: Added boxes for known WG issues throught the document</li>
|
|
<li>2011-05-25: Deleted “Structure of this Document” section, it added no value beyond the TOC</li>
|
|
<li>2011-05-25: Implemented resolution of <a href="http://www.w3.org/2011/rdf-wg/track/issues/40">ISSUE-40: Skolemization advice in the RDF dcocument</a> by adding a section on <a href="#section-skolemization">Replacing Blank Nodes with IRIs</a></li>
|
|
<li>2011-05-25: rdf:XMLLiteral is disjoint from any datatype not explicitly related to it, per erratum <a href="http://www.w3.org/2001/sw/RDFCore/errata#concept-xmlliteral">[concept-xmlliteral]</a></li>
|
|
<li>2011-05-25: Added Conformance section with RFC2119 reference</li>
|
|
<li>2011-05-25: Updated all W3C references to latest editions, and Unicode from v3 to v4</li>
|
|
<li>2011-05-24: Converted to ReSpec, changed metadata to reflect RDF 1.1</li>
|
|
</ul>
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<div id="references" class="appendix section" typeof="bibo:Chapter" about="#references"><!--OddPage--><h2><span class="secno">B. </span>References</h2><div id="normative-references" typeof="bibo:Chapter" about="#normative-references" class="section"><h3><span class="secno">B.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-BCP47">[BCP47]</dt><dd rel="dcterms:requires">A. Phillips; M. Davis. <a href="http://tools.ietf.org/html/bcp47"><cite>Tags for Identifying Languages</cite></a> September 2009. IETF Best Current Practice. URL: <a href="http://tools.ietf.org/html/bcp47">http://tools.ietf.org/html/bcp47</a>
|
|
</dd><dt id="bib-IRI">[IRI]</dt><dd rel="dcterms:requires">M. Duerst, M. Suignard. <a href="http://www.ietf.org/rfc/rfc3987.txt"><cite>Internationalized Resource Identifiers (IRI).</cite></a> January 2005. Internet RFC 3987. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3987.txt</a>
|
|
</dd><dt id="bib-NFC">[NFC]</dt><dd rel="dcterms:requires">M. Davis, Ken Whistler. <a href="http://www.unicode.org/reports/tr15/"><cite>TR15, Unicode Normalization Forms.</cite></a>. 17 September 2010, URL: <a href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</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-SCHEMA">[RDF-SCHEMA]</dt><dd rel="dcterms:requires">Dan Brickley; Ramanathan V. Guha. <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210"><cite>RDF Vocabulary Description Language 1.0: RDF Schema.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210">http://www.w3.org/TR/2004/REC-rdf-schema-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-UNICODE">[UNICODE]</dt><dd rel="dcterms:requires">The Unicode Consortium. <a href="http://www.unicode.org/unicode/standard/versions/enumeratedversions.html"><cite>The Unicode Standard.</cite></a> 2003. Defined by: The Unicode Standard, Version 4.0 (Boston, MA, Addison-Wesley, ISBN 0-321-18578-1), as updated from time to time by the publication of new versions URL: <a href="http://www.unicode.org/unicode/standard/versions/enumeratedversions.html">http://www.unicode.org/unicode/standard/versions/enumeratedversions.html</a>
|
|
</dd><dt id="bib-UTF-8">[UTF-8]</dt><dd rel="dcterms:requires">F. Yergeau. <a href="http://www.ietf.org/rfc/rfc3629.txt"><cite>UTF-8, a transformation format of ISO 10646</cite></a>. IETF RFC 3629. November 2003. URL: <a href="http://www.ietf.org/rfc/rfc3629.txt">http://www.ietf.org/rfc/rfc3629.txt</a>
|
|
</dd><dt id="bib-XML-EXC-C14N">[XML-EXC-C14N]</dt><dd rel="dcterms:requires">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-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">[XML10]</dt><dd rel="dcterms:requires">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-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">B.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-CHARMOD">[CHARMOD]</dt><dd rel="dcterms:references">Martin J. Dürst; et al. <a href="http://www.w3.org/TR/2005/REC-charmod-20050215"><cite>Character Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February 2005. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2005/REC-charmod-20050215">http://www.w3.org/TR/2005/REC-charmod-20050215</a>
|
|
</dd><dt id="bib-N-TRIPLES">[N-TRIPLES]</dt><dd rel="dcterms:references">Jan Grant; Dave Beckett. <a href="http://www.w3.org/TR/rdf-testcases/#ntriples"><cite>N-Triples</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/rdf-testcases/#ntriples">http://www.w3.org/TR/rdf-testcases/#ntriples</a>
|
|
</dd><dt id="bib-RDF-MIME-TYPE">[RDF-MIME-TYPE]</dt><dd rel="dcterms:references"><a href="http://www.iana.org/assignments/media-types/"><cite>MIME Media Types</cite></a>, The Internet Assigned Numbers Authority (IANA). This document is http://www.iana.org/assignments/media-types/ . The <a href="http://www.w3.org/2001/sw/RDFCore/mediatype-registration">registration for <code>application/rdf+xml</code></a> is archived at http://www.w3.org/2001/sw/RDFCore/mediatype-registration .
|
|
</dd><dt id="bib-RDF-PLAINLITERAL">[RDF-PLAINLITERAL]</dt><dd rel="dcterms:references">Jie Bao; Sandro Hawke; Boris Motik; Peter F. Patel-Schneider; Axel Polleres. <a href="http://www.w3.org/TR/2009/REC-rdf-plain-literal-20091027/"><cite>rdf:PlainLiteral: A Datatype for RDF Plain Literals.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-rdf-plain-literal-20091027/">http://www.w3.org/TR/2009/REC-rdf-plain-literal-20091027/</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-GRAMMAR">[RDF-SYNTAX-GRAMMAR]</dt><dd rel="dcterms:references">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-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-TURTLE-TR">[TURTLE-TR]</dt><dd rel="dcterms:references">Eric Prud'hommeaux, Gavin Carothers. <a href="http://www.w3.org/TR/2011/WD-turtle-20110809/"><cite>Turtle: Terse RDF Triple Language.</cite></a> 09 August 2011. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2011/WD-turtle-20110809/">http://www.w3.org/TR/2011/WD-turtle-20110809/</a>
|
|
</dd><dt id="bib-URI">[URI]</dt><dd rel="dcterms:references">T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifiers (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-WELL-KNOWN">[WELL-KNOWN]</dt><dd rel="dcterms:references">M. Nottingham; E. Hammer-Lahav. <a href="http://tools.ietf.org/html/rfc5785"><cite>Defining Well-Known Uniform Resource Identifiers (URIs).</cite></a> April 2010. Internet RFC 5785. URL: <a href="http://tools.ietf.org/html/rfc5785">http://tools.ietf.org/html/rfc5785</a>
|
|
</dd><dt id="bib-XHTML10">[XHTML10]</dt><dd rel="dcterms:references">Steven Pemberton. <a href="http://www.w3.org/TR/2002/REC-xhtml1-20020801/"><cite>XHTML™ 1.0 The Extensible HyperText Markup Language (Second Edition).</cite></a> 1 August 2002. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2002/REC-xhtml1-20020801/">http://www.w3.org/TR/2002/REC-xhtml1-20020801/</a>
|
|
</dd><dt id="bib-XML-INFOSET">[XML-INFOSET]</dt><dd rel="dcterms:references">John Cowan; Richard Tobin. <a href="http://www.w3.org/TR/2004/REC-xml-infoset-20040204/"><cite>XML Information Set (Second Edition).</cite></a> 4 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-xml-infoset-20040204/">http://www.w3.org/TR/2004/REC-xml-infoset-20040204/</a>
|
|
</dd><dt id="bib-XML11">[XML11]</dt><dd rel="dcterms:references">Eve Maler; et al. <a href="http://www.w3.org/TR/2006/REC-xml11-20060816"><cite>Extensible Markup Language (XML) 1.1 (Second Edition).</cite></a> 16 August 2006. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2006/REC-xml11-20060816">http://www.w3.org/TR/2006/REC-xml11-20060816</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><dt id="bib-XPATH">[XPATH]</dt><dd rel="dcterms:references">James Clark; Steven DeRose. <a href="http://www.w3.org/TR/1999/REC-xpath-19991116/"><cite>XML Path Language (XPath) Version 1.0.</cite></a> 16 November 1999. W3C Recommendation. URL: <a href="http://www.w3.org/TR/1999/REC-xpath-19991116/">http://www.w3.org/TR/1999/REC-xpath-19991116/</a>
|
|
</dd></dl></div></div></body></html>
|