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2269 lines
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2269 lines
88 KiB
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<body>
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<div class="head">
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<a href="http://www.w3.org/"><img height="48" width="72" alt=
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"W3C" src="http://www.w3.org/Icons/w3c_home" /></a>
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<h1 id="title">Resource Description Framework (RDF):<br />
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Concepts and Abstract Syntax</h1>
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<h2 id="doctype">W3C Working Draft 23 January 2003</h2>
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<dl>
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<dt>This version:</dt>
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<dd><a href=
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"http://www.w3.org/TR/2003/WD-rdf-concepts-20030123/">http://www.w3.org/TR/2003/WD-rdf-concepts-20030123/</a></dd>
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<dt>Latest version:</dt>
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<dd><a href=
|
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"http://www.w3.org/TR/rdf-concepts/">http://www.w3.org/TR/rdf-concepts/</a></dd>
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<dt>Previous version:</dt>
|
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|
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<dd><a href=
|
|
"http://www.w3.org/TR/2002/WD-rdf-concepts-20021108/">http://www.w3.org/TR/2002/WD-rdf-concepts-20021108/</a></dd>
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|
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<dt>Editors:</dt>
|
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<dd><a href="http://www.ninebynine.org/">Graham Klyne</a> (Nine
|
|
by Nine), <<a href=
|
|
"mailto:GK@NineByNine.org">gk@ninebynine.org</a>></dd>
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<dd><a href="http://www-uk.hpl.hp.com/people/jjc/">Jeremy J.
|
|
Carroll</a> (Hewlett Packard Labs), <<a href=
|
|
"mailto:jjc@hpl.hp.com">jjc@hpl.hp.com</a>></dd>
|
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<dt>Series editor:</dt>
|
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<dd><a href="http://www-uk.hpl.hp.com/people/bwm/">Brian
|
|
McBride</a> (Hewlett Packard Labs) <<a href=
|
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"mailto:bwm@hplb.hpl.hp.com">bwm@hplb.hpl.hp.com</a>></dd>
|
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</dl>
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<p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"> Copyright</a> © 2003 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.lcs.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.org/"><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>, <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-software">software licensing</a> rules apply.</p>
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<hr title="Separator for header" />
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</div>
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<h2 class="nonum"><a id="abstract" name=
|
|
"abstract">Abstract</a></h2>
|
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|
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<p>The Resource Description Framework (RDF) is a framework for
|
|
representing information in the Web.</p>
|
|
|
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<p>This document 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 design goals, meaning of
|
|
RDF documents, key concepts, datatyping, character normalization
|
|
and handling of URI references.</p>
|
|
|
|
<h2 class="nonum"><a id="status" name="status">Status of this
|
|
Document</a></h2>
|
|
|
|
<p>This is a W3C
|
|
<a href="http://www.w3.org/Consortium/Process-20010719/tr.html#last-call">Last Call Working Draft</a>
|
|
of the <a href="http://www.w3.org/2001/sw/RDFCore/">RDF Core Working Group</a>
|
|
and has been produced as part of the W3C
|
|
<a href="http://www.w3.org/2001/sw/">Semantic Web Activity</a>
|
|
(<a href="http://www.w3.org/2001/sw/Activity">Activity Statement</a>).</p>
|
|
|
|
<p>This document is in the Last Call review period, which ends on
|
|
21 February 2003. This document has been endorsed by the RDF
|
|
Core Working Group.</p>
|
|
|
|
<p>This document is being released for review by W3C Members and
|
|
other interested parties to encourage feedback and comments,
|
|
especially with regard to how the changes made affect existing
|
|
implementations and content.</p>
|
|
|
|
|
|
<p>In conformance with
|
|
<a href="http://www.w3.org/Consortium/Process-20010719/#ipr">W3C policy</a>
|
|
requirements, known patent and
|
|
<acronym title="Intellectual Property Rights">IPR</acronym>
|
|
constraints associated with this Working Draft are detailed on the
|
|
<a href="http://www.w3.org/2001/sw/RDFCore/ipr-statements" rel="disclosure">RDF Core Working Group Patent Disclosure</a> page.</p>
|
|
|
|
<p>Comments on this document are invited and should be sent to the
|
|
public mailing list
|
|
<a href="mailto:www-rdf-comments@w3.org">www-rdf-comments@w3.org</a>.
|
|
An archive of comments is available at
|
|
<a href="http://lists.w3.org/Archives/Public/www-rdf-comments/">http://lists.w3.org/Archives/Public/www-rdf-comments/</a>.
|
|
</p>
|
|
|
|
<p>This is a public W3C Last Call Working Draft for review by W3C
|
|
Members and other interested parties. This section describes the
|
|
status of this document at the time of its publication. It is a draft
|
|
document and may be updated, replaced, or obsoleted by other
|
|
documents at any time. It is inappropriate to use W3C Working Drafts
|
|
as reference material or to cite as other than "work in progress". A
|
|
list of current W3C Recommendations and other technical documents can
|
|
be found at <a href="/TR/">http://www.w3.org/TR/</a>.
|
|
</p>
|
|
|
|
<div class="toc">
|
|
<h2 class="nonum"><a id="contents" name="contents">Table of
|
|
Contents</a></h2>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline">
|
|
<a href="#section-Introduction"><strong>1.
|
|
Introduction</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href="#section-Structure">1.1
|
|
Structure of this Document</a></li>
|
|
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Overview"><strong>2. Motivations and Goals</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href="#section-motivation">2.1
|
|
Motivation</a></li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-design-goals">2.2 Design Goals</a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href="#section-simple-data-model">2.2.1 A
|
|
Simple Data Model</a></li>
|
|
|
|
<li class="tocline"><a href="#section-formal-semantics">2.2.2 Formal
|
|
Semantics and Inference</a></li>
|
|
|
|
<li class="tocline"><a href="#section-extensible-vocab">2.2.3
|
|
Extensible URI-based Vocabulary</a></li>
|
|
|
|
<li class="tocline"><a href="#section-xml-serialization">2.2.4
|
|
XML-based Syntax</a></li>
|
|
|
|
<li class="tocline"><a href="#section-use-xsd">2.2.5 Use
|
|
XML Schema Datatypes</a></li>
|
|
|
|
<li class="tocline"><a href="#section-anyone">2.2.6 Anyone
|
|
Can Make Simple Assertions About Anything</a></li>
|
|
|
|
<li class="tocline"><a href="#section-expression-simple">2.2.7
|
|
Arbitrary Expression of Simple Facts</a></li>
|
|
|
|
<li class="tocline"><a href="#section-agreements">2.2.8 A
|
|
Basis for Binding Agreements</a></li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Concepts"><strong>3. RDF Concepts</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href="#section-data-model">3.1 Graph
|
|
Data Model</a></li>
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-URI-Vocabulary">3.2 URI-based Vocabulary
|
|
and Node Identification</a></li>
|
|
|
|
<li class="tocline"><a href="#section-Datatypes">3.3
|
|
Datatypes (Normative)</a></li>
|
|
|
|
<li class="tocline"><a href="#section-Literals">3.4
|
|
Literals</a></li>
|
|
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-SimpleFacts">3.5 Representation of Simple
|
|
Facts</a></li>
|
|
|
|
<li class="tocline"><a href="#section-Entailment">3.6
|
|
Entailment</a></li>
|
|
<li class="tocline"><a href="#section-URIspaces">3.7 RDF
|
|
Core URI Vocabulary and Namespaces</a></li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Meaning"><strong>4. Meaning of RDF (Normative)</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href=
|
|
"#section-AssertedForm">4.1 Asserted and Non-asserted
|
|
Forms</a></li>
|
|
|
|
<li class="tocline"><a href="#section-Social">2.4.2
|
|
Social Meaning</a></li>
|
|
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-authority">4.3 Authoritative Definition
|
|
of Terms</a></li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Interaction">4.4 Interaction
|
|
Between Social and Formal Meaning</a>
|
|
|
|
</li>
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-InteractionExample">4.5
|
|
Example (Informative)</a></li>
|
|
</ul>
|
|
</li>
|
|
|
|
|
|
<li class="tocline"><a href="#section-XMLLiteral"><strong>5.
|
|
XML Content within an RDF Graph (Normative)</strong></a></li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Graph-syntax"><strong>6. Abstract
|
|
Syntax (Normative)</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href="#section-triples">6.1 RDF
|
|
Triples</a></li>
|
|
|
|
<li class="tocline"><a href="#section-rdf-graph">6.2 RDF
|
|
Graph</a></li>
|
|
|
|
<li class="tocline"><a href="#section-graph-equality">6.3 Graph
|
|
Equality</a></li>
|
|
|
|
<li class="tocline"><a href="#section-Graph-URIref">6.4 RDF
|
|
URI References</a></li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-Graph-Literal">6.5 RDF Literals</a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href=
|
|
"#section-Literal-Equality">6.5.1 Literal
|
|
Equality</a></li>
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-Literal-Value">6.5.2 The Value Corresponding
|
|
to a Typed Literal</a></li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="tocline"><a href="#section-blank-nodes">6.6 Blank Nodes</a></li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-fragID"><strong>7. Fragment Identifiers
|
|
</strong></a>
|
|
</li>
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-Acknowledgments"><strong>8.
|
|
Acknowledgments</strong></a></li>
|
|
|
|
<li class="tocline">
|
|
<a href="#section-References"><strong>9.
|
|
References</strong></a>
|
|
|
|
<ul class="toc">
|
|
<li class="tocline"><a href=
|
|
"#section-Normative-References">9.1 Normative
|
|
References</a></li>
|
|
|
|
<li class="tocline"><a href=
|
|
"#section-Informative-References">9.2 Informational
|
|
References</a></li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
</div>
|
|
<hr />
|
|
|
|
<h2><a id="section-Introduction" name="section-Introduction">1.
|
|
Introduction</a></h2>
|
|
|
|
<p>The Resource Description Framework (RDF) is a framework for
|
|
representing information in the Web.</p>
|
|
|
|
<p>This document 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 design goals, meaning of
|
|
RDF documents, key concepts, datatyping, character normalization
|
|
and handling of URI references.</p>
|
|
|
|
<p>Normative documentation of the RDF core falls into the following
|
|
areas:</p>
|
|
|
|
<ul>
|
|
<li>XML serialization syntax [<a href=
|
|
"#ref-rdf-syntax">RDF-SYNTAX</a>],</li>
|
|
|
|
<li>formal semantics [<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>], and</li>
|
|
|
|
<li>this document.</li>
|
|
</ul>
|
|
|
|
<p>Within this document, normative sections are explicitly labelled as such.
|
|
Explicit notes are informative.</p>
|
|
|
|
<p>The framework is designed so that vocabularies can be layered on
|
|
top of a core. The RDF core and RDF vocabulary definition (RDF schema)
|
|
languages
|
|
[<a href="#ref-rdf-vocabulary">RDF-VOCABULARY</a>] are the first
|
|
such vocabularies.
|
|
|
|
Others (cf. OWL [<a href="#ref-owl">OWL</a>] and
|
|
the applications in the primer
|
|
[<a href=
|
|
"#ref-rdf-primer">RDF-PRIMER</a>]) are in development.</p>
|
|
|
|
<h3><a id="section-Structure" name="section-Structure">1.1
|
|
Structure of this Document</a></h3>
|
|
|
|
<p>In <a href="#section-Overview">section 2</a>,
|
|
the background rationale and design goals
|
|
are introduced.
|
|
Key concepts follow in <a href="#section-Concepts">section 3</a>.
|
|
The meaning of RDF is discussed in <a href="#section-Meaning">section 4</a>,
|
|
including discussion of social mechanisms, the interaction between social
|
|
and formal meaning and the implications of
|
|
publication of an RDF document.</p>
|
|
|
|
|
|
<p>RDF's abstract syntax is a graph, which can be serialized using
|
|
XML (but which is quite distinct from XML's tree-based infoset [<a
|
|
href="#ref-xml-infoset">XML-INFOSET</a>]). The abstract syntax
|
|
captures the fundamental structure of RDF, independently of any
|
|
concrete syntax used for serialization. The formal semantics of RDF
|
|
are defined in terms of the abstract syntax. XML content of
|
|
literals is described in <a href="#section-XMLLiteral">section
|
|
5</a>, and the abstract syntax is defined in <a href=
|
|
"#section-Graph-syntax">section 6</a> of this document.</p>
|
|
|
|
<p><a href="#section-fragID">Section 7</a> discusses the role of fragment
|
|
identifiers in URI references used with RDF.</p>
|
|
|
|
<h2><a id="section-Overview" name="section-Overview">2. Motivations and Goals</a></h2>
|
|
|
|
<p>RDF has an abstract syntax that reflects a simple graph-based
|
|
data model, and formal semantics with a rigorously defined notion
|
|
of entailment providing a basis for well founded deductions in RDF
|
|
data.</p>
|
|
|
|
<h3><a id="section-motivation" name="section-motivation">2.1 Motivation</a></h3>
|
|
|
|
<p>The development of RDF has been motivated by the following uses,
|
|
among others:</p>
|
|
|
|
<ul>
|
|
<li>Web metadata: providing information about Web resources and
|
|
the systems that use them (e.g. content rating, capability
|
|
descriptions, privacy preferences, etc.)</li>
|
|
|
|
<li>Applications that require open rather than constrained
|
|
information models (e.g. scheduling activities, describing
|
|
organizational processes, annotation of Web resources, etc.)</li>
|
|
|
|
<li>To do for machine processable information (application data)
|
|
what the World Wide Web has done for hypertext: to allow data to
|
|
be processed outside the particular environment in which it was
|
|
created, in a fashion that can work at Internet scale.</li>
|
|
|
|
<li>Interworking among applications: combining data from several
|
|
applications to arrive at new information.</li>
|
|
|
|
<li>Automated processing of Web information by software agents:
|
|
the Web is moving from having just human-readable information to
|
|
being a world-wide network of cooperating processes. RDF provides
|
|
a world-wide <i>lingua franca</i> for these processes.</li>
|
|
</ul>
|
|
|
|
<p>RDF is designed to represent information in a minimally
|
|
constraining, flexible way. It can be used in isolated
|
|
applications, where individually designed formats
|
|
might be more direct and easily understood, but RDF's generality offers greater value from
|
|
sharing. The value of information thus increases as it becomes
|
|
accessible to more applications across the entire Internet.</p>
|
|
|
|
<h3><a id="section-design-goals" name="section-design-goals">2.2 Design Goals</a></h3>
|
|
|
|
<p>The design of RDF is intended to meet the following goals:</p>
|
|
|
|
<ul>
|
|
<li>A simple data model</li>
|
|
|
|
<li>Formal semantics and provable inference</li>
|
|
|
|
<li>Extensible URI-based vocabulary</li>
|
|
|
|
<li>XML-based syntax</li>
|
|
|
|
<li>Support use of XML schema datatypes</li>
|
|
|
|
<li>Anyone can make simple assertions about anything</li>
|
|
|
|
<li>Universal expression of simple facts</li>
|
|
|
|
<li>A basis for legally binding agreements</li>
|
|
</ul>
|
|
|
|
<h4><a id="section-simple-data-model" name="section-simple-data-model">2.2.1 A Simple Data
|
|
Model</a></h4>
|
|
|
|
<p>RDF has a simple data model that is easy for applications to
|
|
process and manipulate. The data model is independent of any
|
|
specific serialization syntax.</p>
|
|
|
|
<p class="note"><strong>Note:</strong> the term "model" used here in "data model" has a
|
|
completely different sense to its use in the term "model theory".
|
|
See the RDF model theory specification [<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>]
|
|
for more information about "model
|
|
theory" as used in the literature of mathematics and logic.</p>
|
|
|
|
<h4><a id="section-formal-semantics" name="section-formal-semantics">2.2.2 Formal Semantics
|
|
and Inference</a></h4>
|
|
|
|
<p>RDF has a formal semantics which provides a dependable basis for
|
|
reasoning about the meaning of an RDF expression. In particular, it
|
|
supports rigorously defined notions of entailment which provide a
|
|
basis for defining reliable rules of inference in RDF data.</p>
|
|
|
|
<h4><a id="section-extensible-vocab" name="section-extensible-vocab">2.2.3 Extensible
|
|
URI-based Vocabulary</a></h4>
|
|
|
|
<p>The vocabulary is fully extensible, being based on URIs with
|
|
optional fragment identifiers (<cite>URI references</cite>, or
|
|
<cite>URIrefs</cite>). URI references are used for naming all kinds
|
|
of things in RDF.</p>
|
|
|
|
<p>The other kind of value that appears in RDF data is a
|
|
literal.</p>
|
|
|
|
<h4><a id="section-xml-serialization" name="section-xml-serialization">2.2.4 XML-based
|
|
Syntax</a></h4>
|
|
|
|
<p>RDF has a recommended XML serialization form [<a href=
|
|
"#ref-rdf-syntax">RDF-SYNTAX</a>], which can be used to encode the
|
|
data model for exchange of information among applications.</p>
|
|
|
|
<h4><a id="section-use-xsd" name="section-use-xsd">2.2.5 Use XML Schema
|
|
Datatypes</a></h4>
|
|
|
|
<p>RDF can use values represented according to XML schema datatypes
|
|
[<a href="#ref-xml-schema2">XML-SCHEMA2</a>], thus assisting the
|
|
exchange of information between RDF and other XML applications.</p>
|
|
|
|
<h4><a id="section-anyone" name="section-anyone">2.2.6 Anyone Can Make
|
|
Simple Assertions About Anything</a></h4>
|
|
|
|
<p>To facilitate operation at Internet scale, RDF is an open-world
|
|
framework that allows anyone to make simple assertions about
|
|
anything. In general, it is not assumed that all information about
|
|
any topic is available. A consequence of this is that RDF cannot
|
|
prevent anyone from making assertions that are nonsensical or
|
|
inconsistent with the world as people see it, and applications that
|
|
build upon RDF need to find ways to deal with incomplete and
|
|
conflicting sources of information. (This is where RDF departs from
|
|
more prescriptive approaches to representing data in XML, which aim
|
|
to present information that is well-formed and complete for an
|
|
application's needs.)</p>
|
|
|
|
<h4><a id="section-expression-simple" name="section-expression-simple">2.2.7 Arbitrary
|
|
Expression of Simple Facts</a></h4>
|
|
|
|
<p>RDF can represent arbitrary information that can be expressed as
|
|
simple facts. (What constitutes a simple fact is discussed later,
|
|
in <a href="#section-SimpleFacts">section 3.5</a>)</p>
|
|
|
|
<h4><a id="section-agreements" name="section-agreements">2.2.8 A Basis for
|
|
Binding Agreements</a></h4>
|
|
|
|
<p>RDF is intended to convey assertions that are meaningful to the
|
|
extent that they may, in appropriate contexts, be used to express
|
|
the terms of binding agreements.</p>
|
|
|
|
<p>This goal is explored further in <a href=
|
|
"#section-Social">section 4.2</a> below.</p>
|
|
|
|
<h2><a id="section-Concepts" name="section-Concepts">3. RDF
|
|
Concepts</a></h2>
|
|
|
|
<p>RDF uses the following key concepts:</p>
|
|
|
|
<ul>
|
|
<li>Graph data model</li>
|
|
|
|
<li>URI-based vocabulary</li>
|
|
|
|
<li>Datatypes</li>
|
|
|
|
<li>Literals</li>
|
|
|
|
<li>XML serialization syntax</li>
|
|
|
|
<li>Information as representation of simple facts</li>
|
|
|
|
<li>Entailment</li>
|
|
</ul>
|
|
|
|
<h3><a id="section-data-model" name="section-data-model">3.1 Graph Data
|
|
Model</a></h3>
|
|
|
|
<p>The underlying structure of any expression in RDF can be viewed
|
|
as a directed labelled graph, which consists of nodes and labelled
|
|
directed arcs that link pairs of nodes (these notions are defined
|
|
more formally in <a href="#section-Graph-syntax">section 6</a>).
|
|
The RDF graph is a set of triples:</p>
|
|
|
|
<div class="block">
|
|
<p><img src="http://www.w3.org/TR/rdf-concepts/Graph-ex.gif" alt=
|
|
"image of the RDF triple comprising (subject, predicate, object)"
|
|
height="72" width="361" /></p>
|
|
</div>
|
|
<p>Each property arc represents a statement of a relationship between the things denoted by the nodes that it links, having three parts:</p>
|
|
<ol>
|
|
<li>a <a href="#dfn-property"
|
|
>property</a> that describes some
|
|
relationship (also called a <a href="#dfn-predicate"
|
|
>predicate</a>),</li>
|
|
|
|
<li>a value that is the <a href="#dfn-subject"
|
|
>subject</a> of the statement, and</li>
|
|
|
|
<li>a value that is the <a href="#dfn-object"
|
|
>object</a> of the statement.</li>
|
|
</ol>
|
|
<p>The direction of the arc is significant: it always points toward
|
|
the object of a statement.</p>
|
|
|
|
<p>The meaning of an RDF graph is the conjunction (i.e. logical
|
|
AND) of all the statements that it contains.</p>
|
|
|
|
<h3><a id="section-URI-Vocabulary" name=
|
|
"section-URI-Vocabulary">3.2 URI-based Vocabulary and Node
|
|
Identification</a></h3>
|
|
|
|
<p><a href="#section-Graph-Node" >Nodes</a> in an RDF graph are URIs with
|
|
optional fragment identifiers (<a href="#dfn-URI-reference"
|
|
>URI references</a>, or <dfn><a id=
|
|
"dfn-URIref" name="dfn-URIref">URIrefs</a></dfn>), literals, or
|
|
blank (having no separate form of identification). Arcs are
|
|
labelled with <cite>URI references</cite>. (See [<a href=
|
|
"#ref-uris">URI</a>], section 4, for a description of URI
|
|
reference forms, noting that relative URIs are not used in an RDF
|
|
graph. See also <a href="#section-Graph-URIref">section
|
|
6.4</a>.)</p>
|
|
|
|
<p>The URI reference or literal used as a node identifies what that node
|
|
represents. The label on an arc identifies the relationship between
|
|
the nodes connected by the arc. The arc label may also be a node in
|
|
the graph.</p>
|
|
|
|
<p>A <a href="#dfn-blank-node" >blank
|
|
node</a> is an RDF graph node that is not a URI reference 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, and has
|
|
no globally distinguishing identity.</p>
|
|
|
|
<p>A convention used by some linear representations of an RDF graph
|
|
to allow several statements to reference the same blank node is to
|
|
use a <dfn><a id="dfn-blank-node-id" name="dfn-blank-node-id">blank
|
|
node identifier</a></dfn>, which is a local identifier that can be
|
|
distinguished from all URIs 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.</p>
|
|
|
|
<p>Note that blank node identifiers are <em>not</em> part of the
|
|
RDF abstract syntax, and the representation of statements that use
|
|
blank nodes is entirely dependent on the particular concrete syntax
|
|
used.</p>
|
|
|
|
<h3><a name="section-Datatypes" id="section-Datatypes">3.3
|
|
Datatypes (Normative)</a></h3>
|
|
|
|
<p>Datatypes are used by RDF in the representation of values such
|
|
as integers, floating point numbers and dates.</p>
|
|
<p>RDF uses the datatype abstraction defined by XML Schema Part 2:
|
|
Datatypes [<a href="#ref-xml-schema2">XML-SCHEMA2</a>], and may be used with any datatype definition that conforms to this abstraction, even if not actually defined in terms of XML Schema.</p>
|
|
<p>A <dfn><a id="dfn-datatype-mapping" name=
|
|
"dfn-datatype-mapping">datatype mapping</a></dfn> is a set of pairs
|
|
whose first element belongs to the <dfn><a id="dfn-lexical-space"
|
|
name="dfn-lexical-space">lexical space</a></dfn> of the datatype,
|
|
and the second element belongs to the <dfn><a id="dfn-value-space"
|
|
name="dfn-value-space">value space</a></dfn> of the datatype:</p>
|
|
<ul>
|
|
<li>Each member of the <cite>lexical space</cite> is paired with
|
|
(maps to) exactly one member of the <cite>value
|
|
space</cite>.</li>
|
|
|
|
<li>Each member of the <cite>value space</cite> may be paired with any
|
|
number (including zero) of members of
|
|
the <cite>lexical space</cite> (lexical
|
|
representations for that value).</li>
|
|
</ul>
|
|
|
|
<p>With one exception, the datatypes used in RDF have a
|
|
<var><cite>lexical space</cite></var> consisting of a set of
|
|
strings. The exception is <a href=
|
|
"#dfn-rdf-XMLLiteral" class="code">rdf:XMLLiteral</a>, whose
|
|
lexical space also includes pairs of strings and language
|
|
identifiers. The value obtained through its datatype mapping may
|
|
depend on the language identifier.</p>
|
|
|
|
<p>For example, the datatype 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.">
|
|
<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">Datatype Mapping</th>
|
|
|
|
<td>{<"true", T>, <"1", T>, <"0", F>,
|
|
<"false", F>}</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>RDF predefines just one datatype <a href=
|
|
"#dfn-rdf-XMLLiteral" class="code">rdf:XMLLiteral</a>, used for
|
|
embedding XML in RDF (see <a href="#section-XMLLiteral">section
|
|
5</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 URI references.The predefined XML Schema
|
|
datatypes [<a href="#ref-xml-schema2">XML-SCHEMA2</a>] are expected
|
|
to be widely used for this purpose.</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.</p>
|
|
|
|
<p>The defining authority of a URI
|
|
which identifies a datatype is responsible for specifying the
|
|
datatype's lexical space, value space and datatype mapping.</p>
|
|
|
|
<p>RDF provides no mechanism for defining new datatypes. XML Schema
|
|
Datatypes [<a href="#ref-xml-schema2">XML-SCHEMA2</a>] provides an
|
|
extensibility framework suitable for defining new datatypes for use
|
|
in RDF.</p>
|
|
|
|
<h3><a name="section-Literals" id="section-Literals">3.4
|
|
Literals</a></h3>
|
|
|
|
<p>Literals 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 a URI, 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 arc.</p>
|
|
|
|
<p>Literals may be <cite>plain</cite> or <cite>typed</cite> :</p>
|
|
|
|
<ul>
|
|
<li>A <a href="#dfn-plain-literal" >plain literal</a> is a string combined
|
|
with an optional language identifier. This should be used for
|
|
plain text in a natural language. As recommended in the RDF
|
|
formal semantics [<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>], these plain literals are
|
|
self-denoting.</li>
|
|
|
|
<li>A <a href="#dfn-typed-literal" >typed literal</a> is a string, a
|
|
datatype URI and an optional language identifier. It denotes the
|
|
member of the identified datatype's value space obtained by
|
|
applying the datatype mapping to the literal string.</li>
|
|
</ul>
|
|
|
|
<p>Continuing the example from <a href="#section-Datatypes">section
|
|
3.3</a>, the typed literals which 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.">
|
|
<tr>
|
|
<th>Typed Literal</th>
|
|
|
|
<th>Datatype 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>
|
|
</table>
|
|
|
|
|
|
<h3><a id="section-SimpleFacts" name="section-SimpleFacts">3.5
|
|
Representation of Simple Facts</a></h3>
|
|
|
|
|
|
<p>Some simple facts indicate a relationship between
|
|
two objects.
|
|
Such a fact may be represented as an RDF triple in which the predicate
|
|
names the relationship, and the subject and object denote the two objects.
|
|
|
|
|
|
A familiar representation of such a fact might be
|
|
as a row in a table in a relational database. The table has
|
|
two columns, corresponding to the subject and the object of the
|
|
RDF triple.
|
|
The name of the table corresponds to the predicate
|
|
of the RDF triple. A further familiar representation may be as a
|
|
two place predicate
|
|
in first order logic.</p>
|
|
|
|
<p>
|
|
Relational databases permit a table to have an arbitrary number of columns,
|
|
a row of which expresses information corresponding to a predicate in first
|
|
order logic with an arbitrary number of places. Such a row, or predicate,
|
|
has to be decomposed for representation as RDF triples. A simple form of
|
|
decomposition introduces a new blank node, corresponding to the row, and a
|
|
new triple is introduced for each cell in the row. The subject of each
|
|
triple is the new blank node, the predicate corresponds to the column name,
|
|
and object corresponds to the value in the cell. The new blank node may
|
|
also have an <span class="code">rdf:type</span> property whose value corresponds
|
|
to the table name.
|
|
</p>
|
|
|
|
<p>As an example, consider Figure 5 from the
|
|
[<a href=
|
|
"#ref-rdf-primer">RDF-PRIMER</a>]:
|
|
|
|
</p>
|
|
|
|
|
|
<div class="figure">
|
|
<img src="http://www.w3.org/TR/2002/WD-rdf-primer-20021111/fig5-full" alt=
|
|
"Using a Blank Node" width="100%" /><br />
|
|
RDF Primer Figure 5: Using a Blank Node
|
|
</div>
|
|
|
|
|
|
<p>
|
|
This information might correspond to a row in a table <span class="code">"STAFFADDRESSES"</span>,
|
|
with a primary key
|
|
<span class="code">STAFFID</span>,
|
|
and additional columns
|
|
<span class="code">STREET</span>,
|
|
<span class="code">STATE</span>,
|
|
<span class="code">CITY</span> and
|
|
<span class="code">ZIP</span>.
|
|
</p>
|
|
|
|
<p>
|
|
Thus, a more complex fact is expressed in RDF using a
|
|
conjunction (logical-AND) of simple binary relationships. RDF does not
|
|
provide means to express negation (NOT) or disjunction (OR). The expressive
|
|
power of RDF corresponds to the existential-conjunctive (EC) subset of
|
|
first order logic [<a href=
|
|
"#ref-sowa">Sowa</a>]. </p>
|
|
|
|
<p>Through its use of extensible URI-based vocabularies, RDF
|
|
provides for expression of facts about arbitrary subjects; i.e.
|
|
assertions of named properties about specific named things. A URI
|
|
can be constructed for any thing that can be named, so RDF facts
|
|
can be about any such things. <!--
|
|
And, as noted above, RDF also
|
|
provides for expression of assertions about unnamed things, which
|
|
may be fully identifiable in terms of such assertions [<a
|
|
href="#ref-tap-rbd">TAP-RBD</a>].
|
|
-->
|
|
</p>
|
|
|
|
|
|
<h3><a id="section-Entailment" name="section-Entailment">3.6
|
|
Entailment</a></h3>
|
|
|
|
<p>The ideas on meaning and inference in RDF are underpinned by the
|
|
formal concept of <a href="http://www.w3.org/TR/rdf-mt/#entail">
|
|
<cite>entailment</cite></a>, as
|
|
discussed in the RDF
|
|
semantics document [<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>].
|
|
In brief, an RDF expression A is said to
|
|
<dfn>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>
|
|
|
|
<h3><a id="section-URIspaces" name="section-URIspaces">3.7 RDF Core
|
|
URI Vocabulary and Namespaces (Normative)</a></h3>
|
|
|
|
<p>RDF uses URIs to identify resources and properties. Certain URIs
|
|
are reserved for use by RDF, and may not be used for any purpose
|
|
not sanctioned the RDF specifications. Specifically, URIs with the
|
|
following leading substrings are reserved for RDF core
|
|
vocabulary:</p>
|
|
|
|
<ul>
|
|
<li><span class=
|
|
"code">http://www.w3.org/1999/02/22-rdf-syntax-ns#</span>
|
|
(conventionally associated with namespace prefix <span class=
|
|
"code">rdf:</span>)</li>
|
|
|
|
<li><span class=
|
|
"code">http://www.w3.org/2000/01/rdf-schema#</span>
|
|
(conventionally associated with namespace prefix <span class=
|
|
"code">rdfs:</span>)</li>
|
|
</ul>
|
|
|
|
<p>Used with the RDF/XML serialization, these URI prefix strings
|
|
correspond to XML namespaces [<a href="#ref-namespaces">XML-NS</a>]
|
|
associated with the RDF core vocabulary terms.</p>
|
|
|
|
<div class="note">
|
|
<p><strong>Note:</strong> these namespace URIs are the same as those used in
|
|
earlier RDF documents [<a href="#ref-rdf-ms">RDF-MS</a>] [<a
|
|
href="#ref-rdf-schema">RDF-SCHEMA</a>].</p>
|
|
|
|
<p class="todo">[[[<b>NOTE FOR REVIEWERS:</b> Some terms in
|
|
these namespaces have been deprecated, some have been added, and
|
|
some RDF schema terms have had their meaning changed. We invite
|
|
community feedback regarding the relative costs of adopting these
|
|
changes under the old namespace URIs vs creating new URIs for
|
|
this revision of RDF.]]]</p>
|
|
</div>
|
|
|
|
<p>Vocabulary terms in the <span class="code">rdf:</span> namespace
|
|
are listed in <a href=
|
|
"http://www.w3.org/TR/rdf-syntax-grammar/#section-Namespace">section
|
|
5.1</a> of the RDF syntax specification [<a href=
|
|
"#ref-rdf-syntax">RDF-SYNTAX</a>].</p>
|
|
|
|
<p>Vocabulary terms defined in the <span class="code">rdfs:</span>
|
|
namespace are defined
|
|
in the
|
|
RDF schema vocabulary specification [<a href=
|
|
"#ref-rdf-vocabulary">RDF-VOCABULARY</a>].</p>
|
|
|
|
<h2><a id="section-Meaning" name="section-Meaning">4. Meaning of
|
|
RDF (Normative)</a></h2>
|
|
|
|
<p>There are two aspects to the meaning of an RDF graph. There is
|
|
the formal meaning as determined by the RDF semantics
|
|
[<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>].
|
|
This determines, with
|
|
mathematical precision, the conclusions that can
|
|
logically be drawn from an RDF graph. There is also the social
|
|
meaning of the graph. It is the social meaning that affects what it
|
|
means to people and how it interacts with human social institutions
|
|
such as our systems of law.</p>
|
|
|
|
<h3><a id="section-AssertedForm" name="section-AssertedForm">4.1
|
|
Asserted and Non-asserted Forms</a></h3>
|
|
|
|
<p>RDF/XML expressions, i.e. encodings of RDF graphs, can be used
|
|
to make claims or assertions about the 'real' world. Such
|
|
expressions are said to be <dfn><a id="dfn-asserted" name=
|
|
"dfn-asserted">asserted</a></dfn>.</p>
|
|
|
|
<p>Not every RDF/XML expression is asserted.
|
|
Some may convey
|
|
meaning that is partly determined by the circumstances in which
|
|
they are used. For example, in English, a statement "I don't
|
|
believe that George is a clown" contains the words "George is a
|
|
clown", which, considered in isolation, has the form of an
|
|
assertion that George exhibits certain comic qualities. However,
|
|
considering the whole sentence, no such assertion is considered to
|
|
be made.</p>
|
|
|
|
<h3><a id="section-Social" name="section-Social">4.2 Social
|
|
Meaning</a></h3>
|
|
|
|
<p>When an RDF graph is asserted in the Web, its publisher is
|
|
saying something about their view of the world. Such an assertion
|
|
should be understood to carry the same social import and
|
|
responsibilities as an assertion in any other format. A combination
|
|
of social (e.g. legal) and technical machinery (protocols, file
|
|
formats, publication frameworks) provide the contexts that fix the
|
|
intended meanings of the vocabulary of some piece of RDF, and which
|
|
distinguish assertions from other uses (e.g. citations, denials or
|
|
illustrations).</p>
|
|
|
|
<p>The technical machinery includes protocols for transferring
|
|
information (e.g. HTTP, SMTP) and file formats for encapsulating
|
|
and labelling information (e.g. MIME, XML). A media type,
|
|
<span
|
|
class="code">application/rdf+xml</span> [<a href=
|
|
"#ref-rdf-mime-type">RDF-MIME-TYPE</a>]
|
|
indicates the use of
|
|
RDF/XML as distinct from some other XML that happens to look like
|
|
RDF. Issuing an HTTP GET request and obtaining data with a
|
|
"200 OK" response code is a technical indication that the received
|
|
data was published at the request URI; but data received with a
|
|
"404 Not found" response cannot be considered to be similarly
|
|
published information.</p>
|
|
|
|
<p>The social machinery includes the form of publication:
|
|
publishing some unqualified statements on one's World Wide Web home
|
|
page would generally be taken as an assertion of those statements.
|
|
But publishing the same statements with a qualification, such as
|
|
"here are some common myths", or as part of a rebuttal, would
|
|
likely not be construed as an assertion of the truth of those
|
|
statements. Similar considerations apply to the publication of
|
|
assertions expressed in RDF.</p>
|
|
|
|
<p>
|
|
An RDF graph may contain "defining information" that is opaque to
|
|
logical reasoners. This information may be used by human interpreters of
|
|
RDF information, or programmers writing software to perform specialized
|
|
forms of deduction in the Semantic Web.</p>
|
|
|
|
<h3><a name="section-authority" id=
|
|
"section-authority">4.3 Authoritative Definition of Terms</a></h3>
|
|
<p>
|
|
The social conventions surrounding use of RDF assume that any RDF URI
|
|
reference gains its meaning from some defining individual, organization or
|
|
context. This applies most notably to RDF predicate URI references.
|
|
</p>
|
|
<p>
|
|
These social conventions are rooted in the URI specification [<a href=
|
|
"#ref-uris">URI</a>]
|
|
and
|
|
registration procedures [<a href=
|
|
"#ref-uri-reg">URI-REG</a>]. A URI scheme registration refers to a
|
|
specification of the detailed syntax and interpretation for that scheme,
|
|
from which the defining authority for a given URI may be deduced. In the
|
|
case of http: URIs, the defining specification is the HTTP protocol
|
|
specification [<a href=
|
|
"#ref-http">HTTP</a>], which specifies how to use the HTTP protocol to
|
|
obtain a resource representation from the host named in the URI; thus, the
|
|
owner of the indicated DNS domain controls (observable aspects of) the
|
|
URI's meaning.
|
|
</p>
|
|
<p>
|
|
Thus, the choice of terms used in published RDF is significant in
|
|
determining its meaning, through reference to definitions asserted by the
|
|
defining authorities for those terms.
|
|
</p>
|
|
<p>
|
|
For important documents, the use of third-party vocabulary should be restricted
|
|
to terms defined by trustworthy parties (e.g. recognized standards bodies
|
|
or reputable organizations),
|
|
or that otherwise have socially well-established meanings.
|
|
</p>
|
|
<p>However,
|
|
even when a URI reference can be dereferenced as an RDF/XML
|
|
document, it's use within an
|
|
asserted RDF graph does not
|
|
implicitly assert the contents of the
|
|
referenced document.
|
|
</p>
|
|
|
|
|
|
<h3><a id="section-Interaction" name="section-Interaction">4.4
|
|
Interaction Between Social and Formal Meaning </a></h3>
|
|
|
|
|
|
<p>Human publishers of RDF content commit themselves to the
|
|
mechanically-inferred social obligations.
|
|
</p>
|
|
|
|
<p>The meaning of an RDF document includes
|
|
the social meaning, the formal meaning, and
|
|
the social meaning of the formal entailments.
|
|
The assertion of an RDF graph <var>G</var>,
|
|
when <var>G</var> logically entails <var>G'</var>,
|
|
includes the implicit assertion of <var>G'</var>.
|
|
The implied assertion of <var>G'</var> should be interpreted
|
|
using the same social
|
|
conventions that are reasonably used to
|
|
interpret the assertion of <var>G</var>.</p>
|
|
<!--
|
|
<p>The logical entailment intended with content of
|
|
media type
|
|
<span
|
|
class="code">application/rdf+xml</span> [<a href=
|
|
"#ref-rdf-mime-type">RDF-MIME-TYPE</a>]
|
|
is that defined in the RDF Semantics
|
|
[<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>],
|
|
as <a href="http://www.w3.org/TR/rdf-mt/#XSD-entailment">XSD entailment</a>,
|
|
i.e. respecting the RDF vocabulary, the RDFS vocabulary and
|
|
the XML Schema datatypes.</p>
|
|
|
|
<p>Information within such content, or
|
|
the use of a different media type, may indicate
|
|
the use of a
|
|
<a href="http://www.w3.org/TR/rdf-mt/#dfn-semantic-extension">semantic extension</a> to RDF. When such an extension is indicated, this usually
|
|
indicates that the stronger formal entailment associated with that
|
|
extension is intended as part of the meaning of the RDF.</p>
|
|
|
|
|
|
<p>The social conventions surrounding use of RDF include
|
|
of RDF include the idea that each
|
|
URI is associated with some defining authority or context, from which it
|
|
derives its meaning. See <link>section 2.4.4</link> for further discussion
|
|
of this idea.
|
|
</p>
|
|
|
|
]]
|
|
|
|
|
|
the idea
|
|
that each URI 'belongs to' somebody who has authority and
|
|
responsibility for defining its meaning. The social conventions are
|
|
rooted in the URI specification [<a href="#ref-uris">RFC2396</a>]
|
|
and registration procedures [<a href="#ref-uri-reg">RFC2717</a>]. A
|
|
URI scheme registration refers to a specification of the detailed
|
|
syntax and interpretation for that scheme, from which the defining
|
|
authority for a given URI may be deduced. In the case of
|
|
<var>http:</var> URIs, the defining specification is the HTTP
|
|
protocol specification [RFC2616], which obtains a resource
|
|
representation from the host named in the URI; thus, the owner of
|
|
the host's DNS domain controls (observable aspects of) the URI's
|
|
meaning.</p>
|
|
|
|
<p>Publication of
|
|
RDF, when considered as a social act, constitutes a publication of
|
|
some content that is defined by whatever normal <span class=
|
|
"expression">social</span> conditions are used by the publishers of
|
|
any terms in the RDF to define the meanings of those terms, even if
|
|
those meanings and definitions are not accessible to the formal
|
|
semantics of RDF; and, moreover, those meanings are preserved under
|
|
any formally sanctioned inference processes. </p>
|
|
-->
|
|
|
|
<h3><a id="section-InteractionExample" name=
|
|
"section-InteractionExample">4.5 Example (Informative)</a></h3>
|
|
|
|
<p>Imagine two websites publishing the following RDF:</p>
|
|
|
|
<table border="0" cellspacing="2" cellpadding="4" summary=
|
|
"This table shows RDF triples found in two different websites:
|
|
concerning the terms A:Clown and B:Comic.">
|
|
<tr>
|
|
<td colspan="3" valign="top">(A) <span class=
|
|
"expression">http://insult.example.com/lexicon#<br />
|
|
</span> asserts the following, and this is all that one can
|
|
find on the website about that term:</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="code" valign="top">A:Clown</td>
|
|
|
|
<td class="code" valign="top">rdf:type</td>
|
|
|
|
<td class="code" valign="top">rdfs:Class .</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="code" valign="top">A:Clown</td>
|
|
|
|
<td class="code" valign="top">rdfs:comment</td>
|
|
|
|
<td class="code" valign="top">"A class of foolish people, whose
|
|
pronouncements are probably ill-considered and not to be taken
|
|
seriously" .</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="3" valign="top"><br />
|
|
(B) <span class=
|
|
"expression">http://AngloSaxon.example.org/lexicon#</span><br />
|
|
|
|
asserts:</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="code" valign="top">B:Comic</td>
|
|
|
|
<td class="code" valign="top">rdf:subClassOf</td>
|
|
|
|
<td class="code" valign="top">
|
|
<http://insult.example.com/lexicon#Clown> .</td>
|
|
</tr>
|
|
</table>
|
|
<p>
|
|
Imagine also a third, using the vocabulary previously defined
|
|
by the first two.</p>
|
|
<table border="0" cellspacing="2" cellpadding="4" summary=
|
|
"This table shows an RDF triple found in a third website.">
|
|
<tr>
|
|
<td colspan="3" valign="top">
|
|
<p><br />
|
|
(C) <span class=
|
|
"expression">http://skunk.example.org/</span><br />
|
|
asserts the following, assuming that <span class=
|
|
"expression">C:JohnSmith</span> is understood to refer to
|
|
some particular person:</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="code" valign="top">C:JohnSmith</td>
|
|
|
|
<td class="code" valign="top">rdf:type</td>
|
|
|
|
<td class="code" valign="top">
|
|
<http://AngloSaxon.example.org/lexicon#Comic> .</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>Now, it follows by the formal RDF model theory that these three
|
|
together entail:</p>
|
|
|
|
<table border="0" cellspacing="2" cellpadding="4" summary=
|
|
"This table shows a formal entailment of the two previous tables.">
|
|
<tr>
|
|
<td class="code" valign="top">C:JohnSmith</td>
|
|
|
|
<td class="code" valign="top">rdf:type</td>
|
|
|
|
<td class="code" valign="top">
|
|
A:Clown .</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code" valign="top"><A:Clown></td>
|
|
|
|
<td class="code" valign="top">rdfs:comment</td>
|
|
|
|
<td class="code" valign="top">"A class of foolish people, whose
|
|
pronouncements are probably ill-considered and not to be taken
|
|
seriously" .</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>Given this formal entailment, the
|
|
social context of
|
|
<a href="http://www.w3.org/TR/2002/WD-rdf-schema-20021112/#ch_comment"><span class=
|
|
"expression">rdfs:comment</span></a>
|
|
is understood by referring
|
|
to the
|
|
[<a href="#ref-rdf-vocabulary">RDF-VOCABULARY</a>] which says it provides:
|
|
"a human-readable description of a resource".
|
|
Thus, the person identified as <span class=
|
|
"expression">C:JohnSmith</span> might reasonably consider himself
|
|
to be
|
|
insulted.
|
|
</p>
|
|
|
|
<p>Moreover, since the publishers of the third Web site <span class=
|
|
"expression">http://skunk.example.org/</span>
|
|
link <span class=
|
|
"expression">C:JohnSmith</span> to the vocabulary
|
|
previously defined to be insulting, it is they who have insulted
|
|
<span class=
|
|
"expression">C:JohnSmith</span>.</p>
|
|
|
|
<!--
|
|
<p>which Why? Not because of the RDF model theory, which merely says
|
|
he is in some class about which nothing can be <em>formally</em>
|
|
inferred. However, the <span class="expression">rdfs:comment</span>
|
|
associated with that class name by the owner of that name provides
|
|
the insulting content, <em>in the social context of Web
|
|
publication</em>, even though it cannot be formally inferred via
|
|
the RDF inference rules.</p>
|
|
|
|
<p>But who has insulted the identified person? A merely defined the
|
|
term; B does not mention him in particular, so even A and B
|
|
together do not constitute a personal insult. And C might argue
|
|
that although he refers to the person, he only asserts that he is a
|
|
comic, which is not in itself grounds for a libel suit. However,
|
|
one could reasonably claim that C is to blame, since C uses not a
|
|
generic term 'Comic', but a particular URI reference which is
|
|
defined by its owner (B) in a way which is clearly insulting, since
|
|
B in turn explicitly refers to, and uses, the term defined by A.
|
|
Thus, C's use of a B-defined term suggests a clear intent by C to
|
|
convey a meaning defined by B, by virtue of a definition by A,
|
|
which is insulting.</p>
|
|
|
|
<p>By using the specific name <span class=
|
|
"expression">http://AngloSaxon.example.org/lexicon#Comic</span>
|
|
instead of some term defined in, say, a glossary of job
|
|
descriptions, B has explicitly removed his use of the term 'Clown'
|
|
from any formal connection with people who are entertainers. In
|
|
order to succeed in his probable intent of making a generic slander
|
|
against these people, B should have used a term that was defined by
|
|
someone else, such as:</p>
|
|
|
|
<table width="100%" border="0" cellspacing="2" cellpadding="4"
|
|
summary=
|
|
"This table shows the triple: http://www.entertainers.com/glossary#Comic rdfs:subClassOf http://insult.com/lexicon#Clown.">
|
|
<tr>
|
|
<td class="code" colspan="3" valign="top">
|
|
<http://entertainers.example.com/glossary#Comic><br />
|
|
rdfs:subClassOf
|
|
<http://insult.example.com/lexicon#Clown> .</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<p>and then if C had also used this first URI reference, then in
|
|
spite of a similar formal inference chain generating the insulting
|
|
conclusion about <span class="expression">C:JohnSmith</span>, there
|
|
would be nobody to sue, since now C would indeed have simply made a
|
|
harmless observation about his occupation, and B's assertion, while
|
|
indeed arguably offensive, makes no reference to him in
|
|
particular.</p>
|
|
-->
|
|
|
|
|
|
|
|
<h2><a id="section-XMLLiteral" name="section-XMLLiteral">5. XML
|
|
Content within an RDF Graph (Normative)</a></h2>
|
|
|
|
<p>RDF provides for XML content as a possible literal value. This
|
|
typically originates from the use of
|
|
<span class="code">rdf:parseType="Literal"</span> in the RDF/XML Syntax [<a
|
|
href="#ref-rdf-syntax">RDF-SYNTAX</a>].</p>
|
|
|
|
<p>Such content is indicated in an RDF graph using a typed literal
|
|
whose datatype is a special built-in datatype,
|
|
<span class="code">rdf:XMLLiteral</span>.</p>
|
|
|
|
<p>As part of the definition of this datatype, an ancillary
|
|
definition is used.</p>
|
|
|
|
<p>The <em>XML document corresponding to</em> a pair <var>( str,
|
|
lang )</var> is formed as follows:</p>
|
|
|
|
<div class="block">
|
|
<p>Concatenate the five strings:</p>
|
|
|
|
<ol>
|
|
<li><span class="code">"<rdf-wrapper xml:lang='"</span></li>
|
|
|
|
<li><var>lang</var></li>
|
|
|
|
<li><span class="code">"'>"</span></li>
|
|
|
|
<li><var>str</var></li>
|
|
|
|
<li><span class="code">"</rdf-wrapper>"</span></li>
|
|
</ol>
|
|
|
|
<p>Encode the resulting Unicode string in UTF-8 to form the
|
|
corresponding XML document.</p>
|
|
|
|
<p>No escaping is applied. The choice of <span class="code">rdf-wrapper</span>
|
|
is fixed but arbitrary.</p>
|
|
</div>
|
|
|
|
<p>The <em>XML document corresponding to</em> a string
|
|
<var>str</var> is formed as the XML document corresponding to the
|
|
pair <var>(str, "")</var>.</p>
|
|
|
|
<p>Using this, the datatype <dfn><a id="dfn-rdfs-XMLLiteral" name= "dfn-rdfs-XMLLiteral" > </a><a id="dfn-rdf-XMLLiteral" name= "dfn-rdf-XMLLiteral" class="code">rdf:XMLLiteral</a></dfn> is
|
|
defined as follows.</p>
|
|
|
|
<dl>
|
|
<dt>The datatype URI</dt>
|
|
|
|
<dd>is
|
|
<span class="code">http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</span>.</dd>
|
|
|
|
<dt>The value space</dt>
|
|
|
|
<dd>
|
|
is the set of all XML documents that:
|
|
|
|
<ul>
|
|
<li>Have root element tag:
|
|
<span class="code"><rdf-wrapper></span></li>
|
|
|
|
<li>Have no attributes on the root element other than
|
|
<span class="code">xml:lang</span></li>
|
|
|
|
<li>are <a href=
|
|
"http://www.w3.org/TR/2001/REC-xml-c14n-20010315#Terminology">
|
|
Canonical XML</a> [<a href="#ref-XML-C14N">XML-C14N</a>]
|
|
(with comments).</li>
|
|
</ul>
|
|
</dd>
|
|
|
|
<dt>The lexical space</dt>
|
|
|
|
<dd>contains all pairs <var>( string, lang )</var> where
|
|
<var>lang</var> is any language identifier [<a href=
|
|
"#ref-rfc-3066">RFC-3066</a>] in lowercase, and
|
|
<span class="code">string</span> is well-balanced, self-contained XML element
|
|
content [<a href="#ref-xml">XML</a>], for which the XML document
|
|
corresponding to the pair is a <a href=
|
|
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-well-formed">well-formed
|
|
XML document</a> <a href="#ref-xml">[XML]</a> that also conforms
|
|
to <a href=
|
|
"http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
|
|
Namespaces</a> <a href="#ref-namespaces">[XML-NS]</a>.</dd>
|
|
|
|
<dd>also contains all strings <span class="code">string</span> which are
|
|
well-balanced, self-contained XML element content [<a href=
|
|
"#ref-xml">XML</a>], and for which the corresponding XML document
|
|
is a <a href=
|
|
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-well-formed">well-formed
|
|
XML document</a> <a href="#ref-xml">[XML]</a> that also conforms
|
|
to <a href=
|
|
"http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
|
|
Namespaces</a> <a href="#ref-namespaces">[XML-NS]</a>.</dd>
|
|
|
|
<dt>The mapping</dt>
|
|
|
|
<dd>is defined as the function that maps a pair or string to the
|
|
<a href=
|
|
"http://www.w3.org/TR/2001/REC-xml-c14n-20010315#Terminology">canonical
|
|
form</a> [<a href="#ref-XML-C14N">XML-C14N</a>] (with comments)
|
|
of the corresponding XML document.</dd>
|
|
</dl>
|
|
|
|
<p class="note"><strong>Reminder:</strong> All other datatypes have a lexical space
|
|
being a set of strings, and a mapping which maps strings to
|
|
values.</p>
|
|
|
|
<p class="note"><strong>Note:</strong> Not all values of this datatype are compliant
|
|
with XML 1.1 [<a href="#ref-xml-1-1">XML 1.1</a>]. 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>
|
|
|
|
<h2><a id="section-Graph-syntax" name="section-Graph-syntax">6.
|
|
Abstract Syntax (Normative)</a></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 equality between RDF graphs. A
|
|
definition of equality is needed to support the RDF Test Cases [<a
|
|
href="#ref-rdf-tests">RDF-TESTS</a>] specification.</p>
|
|
|
|
|
|
<h3><a id="section-triples" name="section-triples">6.1 RDF
|
|
Triples</a><a id="xtocid103646" name="xtocid103646"> </a></h3>
|
|
|
|
<p>An <dfn><a id="dfn-rdf-triple" name="dfn-rdf-triple">RDF
|
|
triple</a></dfn> contains three components:</p>
|
|
|
|
<ul>
|
|
<li>the <dfn><a id="dfn-subject" name="dfn-subject">subject</a></dfn>,
|
|
which is an <a href="#dfn-URI-reference">RDF URI reference</a>
|
|
or a <a href="#dfn-blank-node">blank node</a>
|
|
</li>
|
|
|
|
<li>the <dfn><a id="dfn-predicate" name="dfn-predicate">predicate</a></dfn>, which is an <a href=
|
|
"#dfn-URI-reference">RDF URI reference</a></li>
|
|
|
|
<li>the <dfn><a id="dfn-object" name="dfn-object">object</a></dfn>,
|
|
which is an <a href="#dfn-URI-reference">RDF URI reference</a>,
|
|
a <a href="#dfn-literal">literal</a>
|
|
or a <a href="#dfn-blank-node">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><a name="dfn-property"
|
|
id="dfn-property">property</a></dfn> of the triple.</p>
|
|
|
|
<h3><a id="section-rdf-graph" name="section-rdf-graph">6.2 RDF Graph</a><a id="xtocid103647" name="xtocid103647"> </a></h3>
|
|
|
|
<p>An <dfn><a id="dfn-rdf-graph" name="dfn-rdf-graph">RDF
|
|
graph</a></dfn> is a set of RDF triples.</p>
|
|
|
|
<p>The <dfn><a name="dfn-node" id="dfn-node">nodes</a><a name="section-Graph-Node" id="section-Graph-Node"> </a></dfn> of an RDF graph is the set of subjects and objects of
|
|
triples in the graph.</p>
|
|
|
|
|
|
<h3><a id="section-graph-equality" name="section-graph-equality">6.3 Graph
|
|
Equality</a></h3>
|
|
|
|
<p>Two RDF graphs <var>G</var> and <var>G'</var> are equal if there
|
|
is a bijection <var>M</var> between the nodes of the two graphs,
|
|
such that:</p>
|
|
|
|
<ol>
|
|
<li><var>M(lit)=lit</var> for all <a href=
|
|
"#dfn-literal">RDF literals</a> <var>lit</var> which
|
|
are nodes of either graph.</li>
|
|
|
|
<li><var>M(uri)=uri</var> for all <a href=
|
|
"#dfn-URI-reference">RDF URI references</a> <var>uri</var>
|
|
which are nodes of either graph.</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, there are the same number of blank nodes in the two graphs,
|
|
and <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>
|
|
|
|
|
|
|
|
<h3><a id="section-Graph-URIref" name="section-Graph-URIref">6.4
|
|
RDF URI References</a></h3>
|
|
|
|
|
|
|
|
<p>A <dfn><a id="dfn-URI-reference" name="dfn-URI-reference">URI reference</a></dfn> within an RDF graph (an RDF URI reference) is a
|
|
Unicode string [<a href="#ref-unicode">UNICODE</a>] that:</p>
|
|
|
|
<ul>
|
|
<li>is in Normal Form C [<a href="#ref-nfc">NFC</a>] and</li>
|
|
|
|
<li>
|
|
would produce a
|
|
valid URI character sequence (per RFC2396 [<a href=
|
|
"#ref-uris">URI</a>], sections 2.1)
|
|
when subjected to the encoding described below.
|
|
</li>
|
|
</ul>
|
|
<p>
|
|
The encoding consists of:
|
|
</p>
|
|
<ol>
|
|
<li>encoding the Unicode string as UTF-8
|
|
[<a href=
|
|
"#ref-rfc-2279">RFC-2279</a>], giving a sequence of octet values.
|
|
</li>
|
|
<li>
|
|
%-escaping octets that do not correspond to permitted US-ASCII characters.
|
|
</li>
|
|
</ol>
|
|
<p>
|
|
The disallowed octets that must be %-escaped include all those that do not
|
|
correspond to US-ASCII characters, and the excluded characters listed in
|
|
Section 2.4 of [<a href=
|
|
"#ref-uris">URI</a>], except for the number sign (#), percent sign (%),
|
|
and the square bracket characters re-allowed in [<a href=
|
|
"#ref-rfc-2732">RFC-2732</a>].
|
|
</p>
|
|
<p>
|
|
Disallowed octets must be escaped with the URI escaping mechanism (that is, converted to %HH,
|
|
where HH is the 2-digit hexadecimal numeral corresponding to the octet value).
|
|
</p>
|
|
|
|
|
|
<p>Two RDF URI references are equal if and only if they compare as
|
|
equal, character by character, as Unicode strings.</p>
|
|
|
|
<div class="note">
|
|
<p><strong>Editors' Note:</strong> This section is in the scope of
|
|
the <a href="http://www.w3.org/2001/tag/">TAG</a> issue
|
|
<a href="http://www.w3.org/2001/tag/ilist#IRIEverywhere-27">IRIEverywhere-27</a>.
|
|
The editors are expecting a resolution
|
|
of this issue during the last call period. This may result in updates
|
|
to this section.</p>
|
|
|
|
<p><strong>Note:</strong> RDF URI references are compatible with the <a
|
|
href=
|
|
"http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#anyURI"><cite>
|
|
anyURI</cite></a> datatype as defined by XML schema datatypes [<a
|
|
href="#ref-xml-schema2">XML-SCHEMA2</a>], constrained to be an
|
|
absolute rather than a relative URI reference, and constrained to
|
|
be in Unicode Normal Form C [<a href="#ref-nfc">NFC</a>] (for
|
|
compatibility with [<a href="#ref-charmod">CHARMOD</a>]).</p>
|
|
|
|
<p><strong>Note:</strong> RDF URI references are compatible with <a href=
|
|
"http://www.w3.org/TR/xml-names11/#IRIs">International Resource
|
|
Identifiers</a> as defined by [<a href="#ref-xml-names11">XML
|
|
Namespaces 1.1</a>].</p>
|
|
|
|
<p><strong>Note:</strong> The restriction to absolute URI references is
|
|
found in this abstract syntax. When there is a well-defined base
|
|
URI, concrete syntaxes, such as RDF/XML, may permit relative URIs
|
|
as a shorthand for such absolute URI references.</p>
|
|
</div>
|
|
|
|
<h3><a id="section-Graph-Literal" name="section-Graph-Literal">6.5
|
|
RDF Literals</a></h3>
|
|
|
|
<p>A <dfn><a id="dfn-literal" name="dfn-literal">literal</a></dfn> in an RDF graph
|
|
contains three components called:</p>
|
|
|
|
<ul>
|
|
<li>The <dfn><a id="dfn-lexical-form" name=
|
|
"dfn-lexical-form">lexical form</a></dfn> being a Unicode [<a
|
|
href="#ref-unicode">UNICODE</a>] string in Normal Form C [<a
|
|
href="#ref-nfc">NFC</a>].</li>
|
|
|
|
<li>The <dfn><a id="dfn-language-identifier" name=
|
|
"dfn-language-identifier">language identifier</a></dfn> as
|
|
defined by [<a href="#ref-rfc-3066">RFC-3066</a>], normalized to
|
|
lowercase.</li>
|
|
|
|
<li>The <dfn><a id="dfn-datatype-URI" name=
|
|
"dfn-datatype-URI">datatype URI</a></dfn> being an <a href=
|
|
"#dfn-URI-reference">RDF URI reference</a>.</li>
|
|
</ul>
|
|
|
|
<p>The lexical form is present in all RDF literals; the language
|
|
identifier and the datatype URI may be absent from an RDF
|
|
literal.</p>
|
|
|
|
<p>A <dfn><a id="dfn-plain-literal" name="dfn-plain-literal">plain literal</a></dfn> is one in which the datatype URI is absent.</p>
|
|
|
|
<p>A <dfn><a id="dfn-typed-literal" name="dfn-typed-literal">typed literal</a></dfn> is one in which the datatype URI is present.</p>
|
|
|
|
<div class="note">
|
|
<p><strong>Note:</strong> Literals in which the lexical form begins with a
|
|
composing character (as defined by [<a href=
|
|
"#ref-charmod">CHARMOD</a>]) are allowed however they may cause
|
|
interoperability problems, particularly with XML version 1.1 [<a
|
|
href="#ref-xml-1-1">XML 1.1</a>].</p>
|
|
|
|
<p><strong>Note:</strong> When using the language identifier, care must be
|
|
taken not to confuse language with locale. The language
|
|
identifier only relates to human language text. Presentational
|
|
issues, how to best represent typed data to the end-user, should
|
|
be addressed in end-user applications.</p>
|
|
</div>
|
|
|
|
<h4><a id="section-Literal-Equality" name=
|
|
"section-Literal-Equality">6.5.1 Literal Equality</a></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 identifiers.</li>
|
|
|
|
<li>The language identifiers of the two lexical forms compare
|
|
equal.</li>
|
|
|
|
<li>Either both or neither have datatype URIs.</li>
|
|
|
|
<li>The two datatype URIs, if any, compare equal, character by
|
|
character.</li>
|
|
</ul>
|
|
|
|
<p class="note"><strong>Note:</strong> RDF Literals are distinct and distinguishable
|
|
from RDF URI references; e.g. http://example.org as an RDF
|
|
Literal (untyped, without a language identifier) is not equal to
|
|
http://example.org as an RDF URI reference.</p>
|
|
|
|
<h4><a id="section-Literal-Value" name=
|
|
"section-Literal-Value">6.5.2 The Value Corresponding to a Typed
|
|
Literal</a></h4>
|
|
|
|
<p>The datatype URI 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, URIs such as
|
|
<span class="code">http://www.w3.org/2001/XMLSchema#int</span> are used. The URI
|
|
of the datatype <a href=
|
|
"#section-XMLLiteral" class="code">rdf:XMLLiteral</a> may be used.
|
|
There may be other, implementation dependent, mechanisms by which
|
|
URIs refer to datatypes.</p>
|
|
|
|
<p>The <em>value</em> associated with a typed literal is found by
|
|
applying the datatype mapping associated with the datatype URI to
|
|
the lexical form.
|
|
Exceptionally, if the datatype is <a href=
|
|
"#section-XMLLiteral" class="code">rdf:XMLLiteral</a> and the
|
|
literal has a language identifier, then the datatype mapping is
|
|
applied to the pair form by the lexical form and the language
|
|
identifier.</p>
|
|
|
|
<p>
|
|
If the lexical form is not in
|
|
the lexical space of the datatype associated with the datatype URI,
|
|
then no literal value can be associated with the typed literal.
|
|
Such a case, while in error, is not <em>syntacticly</em> ill-formed.</p>
|
|
|
|
<p>A typed literal for which the datatype does not map the lexical
|
|
form to a value is not syntacticly ill-formed.</p>
|
|
|
|
|
|
|
|
<p class="note"><strong>Note:</strong>
|
|
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
|
|
[<a href=
|
|
"#ref-rdf-semantics">RDF-SEMANTICS</a>]) are usually
|
|
more helpful than syntactic equality (see
|
|
<a href="#section-graph-equality">
|
|
section
|
|
6.3</a>).</p>
|
|
<h3><a id="section-blank-nodes" name="section-blank-nodes">6.6 Blank Nodes</a></h3>
|
|
<p>
|
|
The <dfn><a id="dfn-blank-node" name="dfn-blank-node">blank nodes</a></dfn> in an RDF graph
|
|
are drawn from an infinite set.
|
|
This set of blank nodes, the set of all <a href="#dfn-URI-reference">RDF URI references</a>
|
|
and the set of all <a href="#dfn-literal">literals</a> are pairwise disjoint.
|
|
</p>
|
|
<p>
|
|
Otherwise, this set is arbitrary.
|
|
</p>
|
|
<p>RDF makes no reference to any internal structure of blank nodes.</p>
|
|
<h2><a id="section-fragID" name="section-fragID">7. Fragment
|
|
Identifiers</a></h2>
|
|
|
|
<p>RDF uses an
|
|
<a href="#dfn-URI-reference">
|
|
RDF URI Reference</a>
|
|
|
|
, which may include a fragment
|
|
identifier, as a context free identifier for a resource. RFC 2396
|
|
[<a href="#ref-uris">URI</a>] 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, in an RDF graph, any RDF URI reference consisting of an
|
|
absolute URI and a fragment identifier identifies the same thing as
|
|
the fragment identifier does in an application/rdf+xml [<a href=
|
|
"#ref-rdf-mime-type">RDF-MIME-TYPE</a>] representation of the
|
|
resource identified by the absolute URI component. Thus:</p>
|
|
|
|
<ul>
|
|
<li>we assume that the URI part (i.e. excluding fragment
|
|
identifier) indicates a Web resource with an RDF representation.
|
|
So when <span class="code">eg:someurl#frag</span> is used in an RDF
|
|
document, <span class="code">eg:someurl</span> is presumed to
|
|
designate an RDF document.</li>
|
|
|
|
<li><span class="code">eg:someurl#frag</span> means the thing that
|
|
is indicated, according to the rules of the <span class=
|
|
"code">application/rdf+xml</span> MIME content-type as a
|
|
"fragment" or "view" of the RDF document at <span class=
|
|
"code">eg:someurl</span>. If the document does not exist, or cannot
|
|
be retrieved, 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 interpretation 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 an abstract idea, like Graham Klyne's car or a mythical
|
|
Unicorn.</li>
|
|
|
|
<li>thus, an <span class="code">application/rdf+xml</span>
|
|
document acts as an intermediary between some Web retrievable
|
|
documents (itself, at least, also any other Web retrievable URIs
|
|
that it may use, including schema URIs 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 URI references and their denotation
|
|
that is consistent with the RDF model theory and usage, and also
|
|
with conventional Web behavior.</p>
|
|
|
|
<h2 class="nonum"><a id="section-Acknowledgments" name=
|
|
"section-Acknowledgments">8. Acknowledgments</a></h2>
|
|
|
|
<p>This document contains a significant contribution from Pat
|
|
Hayes, Sergey Melnik and Patrick Stickler, under whose leadership
|
|
was developed the framework described in the RDF family of
|
|
specifications for representing datatyped values, such as integers
|
|
and dates.</p>
|
|
|
|
<p>The editors acknowledge valuable contributions from the
|
|
following: <!--</p>
|
|
|
|
<ul>-->
|
|
<!--<li>-->Frank Manola,<!--</li>-->
|
|
|
|
<!--<li>-->Pat Hayes,<!--</li>-->
|
|
|
|
<!--<li>-->Dan Brickley,<!--</li>-->
|
|
|
|
<!--<li>-->Jos de Roo,<!--</li>-->
|
|
|
|
<!--<li>-->Dave Beckett,<!--</li>-->
|
|
|
|
<!--<li>-->Patrick Stickler,<!--</li>-->
|
|
|
|
<!--<li>-->Peter F. Patel-Schneider,<!--</li>-->
|
|
|
|
<!--<li>-->Jerome Euzenat,<!--</li>-->
|
|
|
|
<!--<li>-->Massimo Marchiori,<!--</li>-->
|
|
|
|
<!--<li>-->Tim Berners-Lee,<!--</li>-->
|
|
|
|
<!--<li>-->Dave Reynolds<!--</li>-->
|
|
|
|
<!--<li>-->and Dan Connolly.<!--</li>-->
|
|
<!--
|
|
<li class="todo">[[[Other contributors]]]</li>
|
|
</ul>
|
|
-->
|
|
</p>
|
|
<p>Jeremy Carroll thanks <a href="mailto:oreste@w3.org">Oreste
|
|
Signore</a>, his host at the <a href="http://www.w3c.it/">W3C
|
|
Office in Italy</a> and <a href="http://www.isti.cnr.it" lang="it"
|
|
xml:lang="it">Istituto di Scienza e Tecnologie dell'Informazione
|
|
"Alessandro Faedo"</a>, part of the <a href="http://www.cnr.it"
|
|
lang="it" xml:lang="it">Consiglio Nazionale delle Ricerche</a>,
|
|
where Jeremy is a visiting researcher.</p>
|
|
|
|
<p>This document is a product of extended deliberations by the
|
|
RDFcore Working Group, whose members have included:
|
|
|
|
<!--</p><ul>-->
|
|
<!--<li>-->Art Barstow (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Dave Beckett (ILRT),<!--</li>-->
|
|
|
|
<!--<li>-->Dan Brickley (ILRT),<!--</li>-->
|
|
|
|
<!--<li>-->Dan Connolly (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Jeremy Carroll (Hewlett Packard),<!--</li>-->
|
|
|
|
<!--<li>-->Ron Daniel (Interwoven Inc),<!--</li>-->
|
|
|
|
<!--<li>-->Bill dehOra (InterX),<!--</li>-->
|
|
|
|
<!--<li>-->Jos De Roo (AGFA),<!--</li>-->
|
|
|
|
<!--<li>-->Jan Grant (ILRT),<!--</li>-->
|
|
|
|
<!--<li>-->Graham Klyne (Nine by Nine),<!--</li>-->
|
|
|
|
<!--<li>-->Frank Manola (MITRE Corporation),<!--</li>-->
|
|
|
|
<!--<li>-->Brian McBride (Hewlett Packard),<!--</li>-->
|
|
|
|
<!--<li>-->Eric Miller (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Stephen Petschulat (IBM),<!--</li>-->
|
|
|
|
<!--<li>-->Patrick Stickler (Nokia),<!--</li>-->
|
|
|
|
<!--<li>-->Aaron Swartz (HWG),<!--</li>-->
|
|
|
|
<!--<li>-->Mike Dean (BBN Technologies / Verizon),<!--</li>-->
|
|
|
|
<!--<li>-->R. V. Guha (Alpiri Inc),<!--</li>-->
|
|
|
|
<!--<li>-->Pat Hayes (IHMC),<!--</li>-->
|
|
|
|
<!--<li>-->Sergey Melnik (Stanford University) and<!--</li>-->
|
|
|
|
<!--<li>-->Martyn Horner (Profium Ltd).<!--</li>-->
|
|
</p><!--</ul>-->
|
|
<p>This specification also 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. RDF and RDF Schema
|
|
Working Group members who contributed to this earlier work are:
|
|
|
|
<!--</p><ul>-->
|
|
<!--<li>-->Nick Arnett (Verity),<!--</li>-->
|
|
|
|
<!--<li>-->Tim Berners-Lee (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Tim Bray (Textuality),<!--</li>-->
|
|
|
|
<!--<li>-->Dan Brickley (ILRT / University of Bristol),<!--</li>-->
|
|
|
|
<!--<li>-->Walter Chang (Adobe),<!--</li>-->
|
|
|
|
<!--<li>-->Sailesh Chutani (Oracle),<!--</li>-->
|
|
|
|
<!--<li>-->Dan Connolly (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Ron Daniel (DATAFUSION),<!--</li>-->
|
|
|
|
<!--<li>-->Charles Frankston (Microsoft),<!--</li>-->
|
|
|
|
<!--<li>-->Patrick Gannon (CommerceNet),<!--</li>-->
|
|
|
|
<!--<li>-->R. V. Guha (Epinions, previously of Netscape
|
|
Communications),<!--</li>-->
|
|
|
|
<!--<li>-->Tom Hill (Apple Computer),<!--</li>-->
|
|
|
|
<!--<li>-->Arthur van Hoff (Marimba),<!--</li>-->
|
|
|
|
<!--<li>-->Renato Iannella (DSTC),<!--</li>-->
|
|
|
|
<!--<li>-->Sandeep Jain (Oracle),<!--</li>-->
|
|
|
|
<!--<li>-->Kevin Jones, (InterMind),<!--</li>-->
|
|
|
|
<!--<li>-->Emiko Kezuka (Digital Vision Laboratories),<!--</li>-->
|
|
|
|
<!--<li>-->Joe Lapp (webMethods Inc.),<!--</li>-->
|
|
|
|
<!--<li>-->Ora Lassila (Nokia Research Center),<!--</li>-->
|
|
|
|
<!--<li>-->Andrew Layman (Microsoft),<!--</li>-->
|
|
|
|
<!--<li>-->Ralph LeVan (OCLC),<!--</li>-->
|
|
|
|
<!--<li>-->John McCarthy (Lawrence Berkeley National Laboratory),<!--</li>-->
|
|
|
|
<!--<li>-->Chris McConnell (Microsoft),<!--</li>-->
|
|
|
|
<!--<li>-->Murray Maloney (Grif),<!--</li>-->
|
|
|
|
<!--<li>-->Michael Mealling (Network Solutions),<!--</li>-->
|
|
|
|
<!--<li>-->Norbert Mikula (DataChannel),<!--</li>-->
|
|
|
|
<!--<li>-->Eric Miller (OCLC),<!--</li>-->
|
|
|
|
<!--<li>-->Jim Miller (W3C, emeritus),<!--</li>-->
|
|
|
|
<!--<li>-->Frank Olken (Lawrence Berkeley National Laboratory),<!--</li>-->
|
|
|
|
<!--<li>-->Jean Paoli (Microsoft),<!--</li>-->
|
|
|
|
<!--<li>-->Sri Raghavan (Digital/Compaq),<!--</li>-->
|
|
|
|
<!--<li>-->Lisa Rein (webMethods Inc.),<!--</li>-->
|
|
|
|
<!--<li>-->Paul Resnick (University of Michigan),<!--</li>-->
|
|
|
|
<!--<li>-->Bill Roberts (KnowledgeCite),<!--</li>-->
|
|
|
|
<!--<li>-->Tsuyoshi Sakata (Digital Vision Laboratories),<!--</li>-->
|
|
|
|
<!--<li>-->Bob Schloss (IBM),<!--</li>-->
|
|
|
|
<!--<li>-->Leon Shklar (Pencom Web Works),<!--</li>-->
|
|
|
|
<!--<li>-->David Singer (IBM),<!--</li>-->
|
|
|
|
<!--<li>-->Wei (William) Song (SISU),<!--</li>-->
|
|
|
|
<!--<li>-->Neel Sundaresan (IBM),<!--</li>-->
|
|
|
|
<!--<li>-->Ralph Swick (W3C),<!--</li>-->
|
|
|
|
<!--<li>-->Naohiko Uramoto (IBM),<!--</li>-->
|
|
|
|
<!--<li>-->Charles Wicksteed (Reuters Ltd.),<!--</li>-->
|
|
|
|
<!--<li>-->Misha Wolf (Reuters Ltd.) and<!--</li>-->
|
|
|
|
<!--<li>-->Lauren Wood (SoftQuad).<!--</li>-->
|
|
<!--</ul>--></p>
|
|
|
|
<h2 class="nonum"><a id="section-References" name=
|
|
"section-References">9. References</a></h2>
|
|
|
|
<h3><a id="section-Normative-References" name=
|
|
"section-Normative-References"></a>9.1 Normative References</h3>
|
|
|
|
<dl>
|
|
<dt><a id="ref-rdf-syntax" name=
|
|
"ref-rdf-syntax"></a>[RDF-SYNTAX]</dt>
|
|
|
|
<dd><i><a href=
|
|
"http://www.w3.org/TR/2002/WD-rdf-syntax-grammar-20021108/">RDF/XML
|
|
Syntax Specification (Revised)</a></i>, Dave Beckett, World Wide
|
|
Web Consortium, 8 November 2002 (work in progress). This version
|
|
of the RDF/XML Syntax Specification (Revised) is
|
|
http://www.w3.org/TR/2002/WD-rdf-syntax-grammar-20021108/. The
|
|
latest version is at <a href=
|
|
"http://www.w3.org/TR/rdf-syntax-grammar/">http://www.w3.org/TR/rdf-syntax-grammar/</a>.</dd>
|
|
|
|
<dt><a id="ref-rdf-semantics" name=
|
|
"ref-rdf-semantics"></a>[RDF-SEMANTICS]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/2002/WD-rdf-mt-20021112/">RDF Semantics</a></cite>,
|
|
P. Hayes, World Wide
|
|
Web Consortium, 12 November 2002 (work in progress).
|
|
This version of the RDF Semantics is
|
|
http://www.w3.org/TR/2002/WD-rdf-mt-20021112/. The latest version
|
|
is at <a
|
|
href="http://www.w3.org/TR/rdf-mt/">http://www.w3.org/TR/rdf-mt/</a>.</dd>
|
|
|
|
<dt><a id="ref-rdf-vocabulary" name=
|
|
"ref-rdf-vocabulary"></a>[RDF-VOCABULARY]</dt>
|
|
|
|
<dd><i><a href="http://www.w3.org/TR/2002/WD-rdf-schema-20021112/">RDF Vocabulary
|
|
Description Language 1.0: RDF Schema</a></i>, Dan Brickley, R.V.
|
|
Guha, World Wide Web Consortium, April 2002 (work in progress).
|
|
This version of the RDF Vocabulary
|
|
Description Language is http://www.w3.org/TR/2002/WD-rdf-schema-20021112/.
|
|
The latest version is at <a href=
|
|
"http://www.w3.org/TR/rdf-schema/">http://www.w3.org/TR/rdf-schema/</a>.</dd>
|
|
|
|
<dt><a id="ref-rdf-mime-type" name=
|
|
"ref-rdf-mime-type"></a>[RDF-MIME-TYPE]</dt>
|
|
|
|
<dd><i><a href=
|
|
"http://www.ietf.org/internet-drafts/draft-swartz-rdfcore-rdfxml-mediatype-01.txt">
|
|
Application/rdf+xml Media Type Registration</a></i>, A. Swartz,
|
|
IETF Internet Draft, March 2002 (work in progress). Version
|
|
available at <a href=
|
|
"http://www.ietf.org/internet-drafts/draft-swartz-rdfcore-rdfxml-mediatype-01.txt">
|
|
http://www.ietf.org/internet-drafts/draft-swartz-rdfcore-rdfxml-mediatype-01.txt</a>.</dd>
|
|
|
|
<dt><a id="ref-xml" name="ref-xml"></a>[XML]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/2000/REC-xml-20001006">Extensible Markup
|
|
Language (XML) 1.0, Second Edition</a></cite>, T. Bray, J. Paoli,
|
|
C.M. Sperberg-McQueen and E. Maler, Editors. World Wide Web
|
|
Consortium. 6 October 2000. This version is
|
|
<span>http://www.w3.org/TR/2000/REC-xml-20001006</span>. The
|
|
latest version of XML is available at <a href=
|
|
"http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a>.</dd>
|
|
|
|
<dt><a id="ref-namespaces" name=
|
|
"ref-namespaces"></a>[XML-NS]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/1999/REC-xml-names-19990114/">Namespaces in
|
|
XML</a></cite>, T. Bray, D. Hollander and A. Layman, Editors.
|
|
World Wide Web Consortium. 14 January 1999. This version is
|
|
<span>http://www.w3.org/TR/1999/REC-xml-names-19990114/</span>.
|
|
The <a href="http://www.w3.org/TR/REC-xml-names/">latest version
|
|
of Namespaces in XML</a> is available at
|
|
http://www.w3.org/TR/REC-xml-names/.</dd>
|
|
|
|
<dt><a id="ref-rfc-2279" name="ref-rfc-2279"></a>[RFC-2279]</dt>
|
|
|
|
<dd><i><a href="http://www.isi.edu/in-notes/rfc2279.txt">RFC 2279
|
|
- UTF-8, a transformation format of ISO 10646</a></i>, F.
|
|
Yergeau, IETF, January 1998. This document is
|
|
http://www.isi.edu/in-notes/rfc2279.txt.</dd>
|
|
|
|
|
|
<dt><a id="ref-uris" name="ref-uris"></a>[URI]</dt>
|
|
|
|
<dd><cite><a href="http://www.isi.edu/in-notes/rfc2396.txt">RFC
|
|
2396 - Uniform Resource Identifiers (URI): Generic
|
|
Syntax</a></cite>, T. Berners-Lee, R. Fielding and L. Masinter,
|
|
IETF, August 1998. This document is
|
|
http://www.isi.edu/in-notes/rfc2396.txt.</dd>
|
|
|
|
<dt><a id="ref-http" name="ref-http"></a>[HTTP]</dt>
|
|
|
|
<dd><cite><a href="http://www.isi.edu/in-notes/rfc2616.txt">RFC
|
|
2616 - Hypertext Transfer Protocol -- HTTP/1.1</a></cite>,
|
|
R. Fielding, UC Irvine, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
|
|
P. Leach,
|
|
T. Berners-Lee,
|
|
IETF, August 1998. This document is
|
|
http://www.isi.edu/in-notes/rfc2616.txt.</dd>
|
|
|
|
<dt><a id="ref-uri-reg" name="ref-uri-reg"></a>[URI-REG]</dt>
|
|
|
|
<dd><cite><a href="http://www.isi.edu/in-notes/rfc2717.txt">RFC
|
|
2717 - Registration Procedures for URL Scheme Names</a></cite>,
|
|
R. Petke and I. King, IETF, November 1999. This document is
|
|
http://www.isi.edu/in-notes/rfc2717.txt.</dd>
|
|
|
|
<dt><a id="ref-rfc-2732" name="ref-rfc-2732"></a>[RFC-2732]</dt>
|
|
|
|
<dd><i><a href="http://www.isi.edu/in-notes/rfc2732.txt">RFC 2732
|
|
- Format for Literal IPv6 Addresses in URL's</a></i>, R. Hinden,
|
|
B. Carpenter and L. Masinter, IETF, December 1999. This document
|
|
is http://www.isi.edu/in-notes/rfc2732.txt.</dd>
|
|
|
|
|
|
<dt><a id="ref-unicode" name="ref-unicode"></a>[UNICODE]</dt>
|
|
|
|
<dd><cite>The Unicode Standard, Version 3</cite>, The Unicode
|
|
Consortium, Addison-Wesley, 2000. ISBN 0-201-61633-5, as updated
|
|
from time to time by the publication of new versions. (See <a
|
|
href=
|
|
"http://www.unicode.org/unicode/standard/versions/">http://www.unicode.org/unicode/standard/versions/</a>
|
|
for the latest version and additional information on versions of
|
|
the standard and of the Unicode Character Database).</dd>
|
|
|
|
<dt><a id="ref-nfc" name="ref-nfc"></a>[NFC]</dt>
|
|
|
|
<dd><a href=
|
|
"http://www.unicode.org/unicode/reports/tr15/"><cite>Unicode
|
|
Normalization Forms,</cite></a> Unicode Standard Annex #15, Mark
|
|
Davis, Martin Dürst. (See <a href=
|
|
"http://www.unicode.org/unicode/reports/tr15/">http://www.unicode.org/unicode/reports/tr15/</a>
|
|
for the latest version).</dd>
|
|
|
|
|
|
<dt><a id="ref-rfc-3066" name="ref-rfc-3066"></a>[RFC-3066]</dt>
|
|
|
|
<dd><i><a href="http://www.isi.edu/in-notes/rfc3066.txt">RFC 3066
|
|
- Tags for the Identification of Languages</a></i>, H.
|
|
Alvestrand, IETF, January 2001. This document is
|
|
http://www.isi.edu/in-notes/rfc3066.txt.</dd>
|
|
|
|
<dt><a id="ref-XML-C14N" name="ref-XML-C14N"></a>[XML-C14N]</dt>
|
|
|
|
<dd><a href=
|
|
"http://www.w3.org/TR/2001/REC-xml-c14n-20010315">Canonical
|
|
XML.</a> J. Boyer. W3C Recommendation, March 2001.</dd>
|
|
|
|
<dd>Available at <a href=
|
|
"http://www.w3.org/TR/2001/REC-xml-c14n-20010315">http://www.w3.org/TR/2001/REC-xml-c14n-20010315</a></dd>
|
|
|
|
<dd>Available at <a href=
|
|
"http://www.ietf.org/rfc/rfc3076.txt">http://www.ietf.org/rfc/rfc3076.txt</a></dd>
|
|
<!--
|
|
<dt><a id="ref-keywords" name="ref-keywords"></a>[KEYWORDS]</dt>
|
|
|
|
<dd><cite><a href="http://www.ietf.org/rfc/rfc2119.txt">RFC 2119
|
|
- Key words for use in RFCs to Indicate Requirement
|
|
Levels</a></cite>, S. Bradner, IETF. March 1997. This document is
|
|
http://www.ietf.org/rfc/rfc2119.txt. <span class="todo">[[[Is
|
|
this used?]]]</span></dd>
|
|
|
|
<dt><a id="ref-rfc3023" name="ref-rfc3023"></a>[RFC-3023]</dt>
|
|
|
|
<dd><cite><a href="http://www.ietf.org/rfc/rfc3023.txt">RFC 3032
|
|
- XML Media Types</a></cite>, M. Murata, S. St.Laurent, D.Kohn,
|
|
IETF, January 2001. This document is
|
|
http://www.ietf.org/rfc/rfc3023.txt.</dd>
|
|
-->
|
|
<dt><a id="ref-xml-schema2" name=
|
|
"ref-xml-schema2"></a>[XML-SCHEMA2]</dt>
|
|
|
|
<dd><cite><a href="http://www.w3.org/TR/xmlschema-2/">XML Schema
|
|
Part 2: Datatypes - W3C Recommendation</a></cite>, World Wide Web
|
|
Consortium, 2 May 2001.</dd>
|
|
|
|
</dl>
|
|
|
|
<h3><a id="section-Informative-References" name=
|
|
"section-Informative-References"></a>9.2 Informational
|
|
References</h3>
|
|
<dl>
|
|
<dt><a id="ref-rdf-tests" name=
|
|
"ref-rdf-tests"></a>[RDF-TESTS]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/2002/WD-rdf-testcases-20021112/">RDF Test
|
|
Cases</a></cite>, Jan Grant and Dave Beckett, Editors. Work in
|
|
progress. World Wide Web Consortium, 29 April 2002. This version
|
|
of the RDF Test Cases is
|
|
<span>http://www.w3.org/TR/2002/WD-rdf-testcases-20021112/</span>.
|
|
The latest version of the RDF Test Cases is at <a href=
|
|
"http://www.w3.org/TR/rdf-testcases/">http://www.w3.org/TR/rdf-testcases/</a>.</dd>
|
|
|
|
|
|
<dt><a id="ref-rdf-primer" name=
|
|
"ref-rdf-primer"></a>[RDF-PRIMER]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/2002/WD-rdf-primer-20020426/">RDF
|
|
Primer</a></cite>, F. Manola, E. Miller, Editors, World Wide Web
|
|
Consortium W3C Working Draft, work in progress, 26 April 2002.
|
|
This version of the RDF Primer is
|
|
http://www.w3.org/TR/2002/WD-rdf-primer-20020426/. The <a href=
|
|
"http://www.w3.org/TR/rdf-primer/">latest version of the RDF
|
|
Primer</a> is at http://www.w3.org/TR/rdf-primer/.</dd>
|
|
|
|
<dt><a id="ref-charmod" name="ref-charmod"></a>[CHARMOD]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/2002/WD-charmod-20020220/">Character Model
|
|
for the World Wide Web 1.0</a></cite>, M. Dürst, F. Yergeau,
|
|
R. Ishida, M. Wolf, A. Freytag, T Texin, Editors, World Wide Web
|
|
Consortium Working Draft, work in progress, 20 February 2002.
|
|
This version of the Character Model is
|
|
http://www.w3.org/TR/2002/WD-charmod-20020220/. The <a href=
|
|
"http://www.w3.org/TR/charmod/">latest version of the Character
|
|
Model</a> is at http://www.w3.org/TR/charmod/.</dd>
|
|
|
|
<dt><a id="ref-xml-1-1" name="ref-xml-1-1"></a>[XML-1.1]</dt>
|
|
|
|
<dd><cite><a href="http://www.w3.org/TR/xml11/">Extensible Markup
|
|
Language (XML) 1.1</a></cite>, John Cowan, Editor. World Wide Web
|
|
Consortium Working Draft 25 April 2002. <i>(Work in
|
|
progress)</i></dd>
|
|
|
|
<dt><a id="ref-xml-names11" name=
|
|
"ref-xml-names11"></a>[XML-NAMESPACES-1.1]</dt>
|
|
|
|
<dd><cite><a href="http://www.w3.org/TR/xml-names11/">Namespaces
|
|
in XML 1.1</a></cite>, Tim Bray, Dave Hollander, Andrew Layman,
|
|
Richard Tobin, Editors. World Wide Web Consortium Working Draft 5
|
|
September 2002. <i>(Work in progress)</i></dd>
|
|
|
|
<dt><a id="ref-xml-infoset" name=
|
|
"ref-xml-infoset"></a>[XML-INFOSET]</dt>
|
|
|
|
<dd><i><a href="http://www.w3.org/TR/xml-infoset/">XML
|
|
Information Set</a></i>, John Cowan and Richard Tobin, W3C
|
|
Recommendation, 24 October 2001. This document is
|
|
http://www.w3.org/TR/xml-infoset/.</dd>
|
|
<!--
|
|
<dt><a id="ref-xmlschema0" name=
|
|
"ref-xmlschema0"></a>[XML-SCHEMA0]</dt>
|
|
|
|
<dd><cite><a href="http://www.w3.org/TR/xmlschema-0/">XML Schema
|
|
Part 0: Primer - W3C Recommendation</a></cite>, World Wide Web
|
|
Consortium, 2 May 2001.</dd>
|
|
|
|
<dt><a id="ref-xmlschema1" name=
|
|
"ref-xmlschema1"></a>[XML-SCHEMA1]</dt>
|
|
|
|
<dd><cite><a href="http://www.w3.org/TR/xmlschema-1/">XML Schema
|
|
Part 1: Structures - W3C Recommendation</a></cite>, World Wide
|
|
Web Consortium, 2 May 2001.</dd>
|
|
-->
|
|
|
|
<dt><a id="ref-owl" name="ref-owl"></a>[OWL]</dt>
|
|
|
|
<dd><a href=
|
|
"http://www.w3.org/TR/2002/WD-owl-ref-20020729/"><i>OWL Web
|
|
Ontology Language 1.0 Reference</i></a>, Mike Dean, Dan Connolly,
|
|
Frank van Harmelen, James Hendler, Ian Horrocks, Deborah L.
|
|
McGuinness, Peter F. Patel-Schneider, and Lynn Andrea Stein. W3C
|
|
Working Draft 29 July 2002. Latest version is available at <a
|
|
href=
|
|
"http://www.w3.org/TR/owl-ref/">http://www.w3.org/TR/owl-ref/</a>.</dd>
|
|
|
|
<dt><a id="ref-sowa" name="ref-sowa"></a>[SOWA]</dt>
|
|
|
|
<dd><i>Knowledge Representation: Logical, Philosophical and
|
|
Computational Foundations</i>, John F. Sowa, Brookes/Cole, 2000.
|
|
ISBN 0-534-94965-7.</dd>
|
|
|
|
<!--
|
|
<dt><a id="ref-notation3" name=
|
|
"ref-notation3"></a>[NOTATION3]</dt>
|
|
|
|
<dd>Tim Berners-Lee, DesignIssues note on N3, ...</dd>
|
|
-->
|
|
<dt><a id="ref-rdf-ms" name="ref-rdf-ms"></a>[RDF-MS]</dt>
|
|
|
|
<dd><cite><a href=
|
|
"http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/">Resource
|
|
Description Framework (RDF) Model and Syntax
|
|
Specification</a></cite>, O. Lassila and R. Swick, Editors. World
|
|
Wide Web Consortium. 22 February 1999. This version is
|
|
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/. The <a href=
|
|
"http://www.w3.org/TR/REC-rdf-syntax/">latest version of RDF
|
|
M&S</a> is available at
|
|
http://www.w3.org/TR/REC-rdf-syntax/.</dd>
|
|
|
|
<dt><a id="ref-rdf-schema" name=
|
|
"ref-rdf-schema"></a>[RDF-SCHEMA]</dt>
|
|
|
|
<dd><i><a href="http://www.w3.org/TR/2000/CR-rdf-schema-20000327/">
|
|
Resource
|
|
Description Framework (RDF) Schema Specification 1.0</a></i>, Dan
|
|
Brickley and R. V. Guha, W3C Candidate Recommendation, 27 March
|
|
2000. This document is http://www.w3.org/TR/2000/CR-rdf-schema-20000327/.</dd>
|
|
<!--
|
|
<dt><a id="ref-tap-rbd" name="ref-tap-rbd"></a>[TAP-RBD]</dt>
|
|
<dd><i><a href="http://www.alpiri.org/protocol/rbd.html">Reference
|
|
by Description</a></i>, R. V. Guha: <a
|
|
href="http://www.alpiri.org/protocol/rbd.html">http://www.alpiri.org/protocol/rbd.html</a>.
|
|
(Related to the TAP project: <a
|
|
href="http://tap.stanford.edu/">http://tap.stanford.edu/</a>).</dd>
|
|
-->
|
|
</dl>
|
|
<hr />
|
|
<div class="metadata">
|
|
<p><a href="metadata.rdf"><img
|
|
src="rdf_meta.gif" alt="RDF/XML Metadata" /></a></p>
|
|
</div>
|
|
</body>
|
|
</html>
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