- From: Manu Sporny via cvs-syncmail <cvsmail@w3.org>
- Date: Sun, 12 Jul 2009 18:36:00 +0000
- To: public-html-commits@w3.org
Update of /sources/public/html5/rdfa
In directory hutz:/tmp/cvs-serv22460/rdfa
Added Files:
rdfa-module.html source
Log Message:
Added first editors draft of HTML5+RDFa module specification and
anolis-generated HTML module.
--- NEW FILE: source ---
<h2>
<dfn>RDFa</dfn>
</h2>
<h3>
Issues
</h3>
<p class="XXX">
This section outlines a number of editorial issues with the RDFa
section of the HTML5 specification.
</p>
<p class="XXX">
In order to provide a module that can be authored, inserted and moved
easily within the HTML5 specification, the RDFa specification section is
being edited separately from the main HTML5 specification source file.
There are two documents that are generated from the RDFa specification
source. The first is the full HTML5 specification, which includes the
RDFa specification section. The second is the stand-alone HTML5+RDFa
document.
</p>
<p class="XXX">
The upside to having two documents generated from the same source mainly
has to do with load-times for the HTML5 specification in web browsers.
Loading the 4MB HTML5 specification can be very slow, even in Firefox
3.5 or Chrome. So for those that want to just look at the RDFa specification
text, there is a much smaller, separate document for that purpose.
</p>
<p class="XXX">
Unfortunately, there are a number of down-sides with this approach. The
first is that the specification language becomes more verbose. The second
is that cross-references within the HTML5 document are impossible due to
a bug/feature in the Anolis specification processor.
<p class="XXX">
These down-sides are not ideal and will eventually be remedied as we find
a way to either fix Anolis or integrate the RDFa document into the HTML5
specification.
</p>
<h3>
Introduction
</h3>
<p>
<em>This section is informative.</em>
</p>
<p>
Starting in 2006, the Semantic Web Deployment Work Group
began work to develop a technology to express semantic data in
XHTML 1.1. This technology was successfully developed and is now
called RDFa (The Resource Description Framework in Attributes).
While HTML provides a mechanism to express the structure of a document
(title, paragraphs, links), RDFa provides a mechanism to express
the meaning of a document (people, places, events).
<p>
<p>
The document, titled "RDFa in XHTML: Syntax and Processing Rules"
[<a href="http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFa</a>], defined
a set of attributes and rules for processing those attributes that
resulted in the output of machine-readable semantic data. While the
document was specific to the XHTML 1.1 member in the HTML family, the
attributes and rules were always intended to operate across any
tree-based structure containing attributes on tree nodes (such as HTML4,
SVG and ODF).
</p>
<p>
While RDFa was initially specified for use in XHTML 1.1, adoption by
a number of large organizations on the Web spurred RDFa's use in non-XHTML
languages. Its use in HTML4 and HTML5, before an official specification
was developed for those languages, caused concern regarding document
conformance.
</p>
<p>
Over the years, the members of the RDFa Task Force
[<a href="http://rdfa.info/">RDFaTF</a>] had discussed the possibility
of applying the same attributes and processing rules outlined in the
XHTML+RDFa specification to all HTML family documents. By design, the
possibility of a unified semantic data expression mechanism between all
HTML and XHTML family documents was squarely in the realm of possibility.
</p>
<p>
This section describes the modifications to the original XHTML+RDFa
specification that permit the use of RDFa in all HTML family documents.
By using the attributes and processing rules described in the
XHTML+RDFa specification and heeding the minor changes in this
section, authors can expect to generate markup that produces the same
semantic data output in HTML4, HTML5 and XHTML5.
</p>
<p>
This section has been prepared by Manu Sporny (President/CEO of Digital
Bazaar, Inc.) in consultation with key members of the
RDFa in XHTML Task Force, the HTML WG, the WHAT WG, and other
interested parties.
</p>
<h3>
Parsing Model
</h3>
<p>
Section 5 of the
[<a href="http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFa</a>] specification
defines a generic processing model for extracting RDF from a
tree-based model. The method of transforming an input document into a
model suited for the RDFa processing rules is intentionally not defined
in the XHTML+RDFa specification. The method of transformation was intended
to be defined in the implementation language, in this case, this section of
the HTML5 specification.
</p>
<p>
In the context of the HTML5 specification, the parsing rules for an input
document in HTML4 and HTML5 are clearly defined. The processing model
defined in Section 5 of the XHTML+RDFa specification should be executed
on the HTML5 DOM. While the HTML5 DOM is not currently stable, a parsing
mechanism built on top of the html5lib library should provide a
mechanism that is guaranteed to eventually provide a stable, tree-based
model for the RDFa processing rules.
</p>
<p>
RDFa's tree-based processing rules enable an input document to be
automatically corrected, cleaned-up, re-arranged, or modified in any
way that is approved by the host language. For example, element nesting
issues in HTML documents may be corrected before the input document is
serialized into the tree-based model on which the RDFa processing rules
will operate.
</p>
<h3>
Conformance Requirements
</h3>
<p>
<em>This section is normative.</em>
</p>
<p>
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [<a class="nref"
href="#ref_RFC2119">RFC2119</a>].
</p>
<p>
Note that all examples in this document are informative, and are not meant
to be interpreted as normative requirements.
</p>
<h3>
Document Conformance
</h3>
<p>
In order for a document to claim that it is a conforming HTML+RDFa document,
it must provide the facilities described as mandatory in this section.
The document conformance criteria are listed below, of which only a subset
are mandatory:
</p>
<ol>
<li>
There should be a DOCTYPE declaration specified prior to the root element
in the document that follows the conventions outlined in the
"The DOCTYPE section" of the HTML5 specification.
</li>
<li>
The root element of the document must follow the conventions outlined
in "The root element" section of the HTML5 specification.
</li>
<li>
There may be a <code>link</code> element contained in the
<code>head</code> element that contains <code>profile</code> for
the the <code>rel</code> attribute and
<code>http://www.w3.org/1999/xhtml/vocab</code> for the <code>href</code>
attribute.
<div class="XXX">
This requires the HTML5 spec to add <code>profile</code> to the list of
allow-able <code>rel</code>-values. This is used as the signalling
mechansim for an RDFa document because the <code>profile</code>
attribute is deprecated in HTML5.
</div>
</li>
</ol>
<h3>
User Agent Conformance
</h3>
<p>
A conforming RDFa user agent must:
<ul>
<li>
Conform to all conformance requirements listed in the
"Conformance requirements" section of the HTML5 specification.
</li>
<li>
Implement all of the features required in the RDFa section of the
HTML5 specification.
</li>
<li>
Implement all of the features specified in the XHTML+RDFa specification,
excluding those features which are specifically overridden by the RDFa
section of the HTML5 specification.
</li>
</ul>
</p>
<h3>
RDFa Processor Conformance
</h3>
<p>
A conforming RDFa Processor must implement all of the mandatory features
specified in the XHTML+RDFa specification. It must also support any
mandatory features specified in the RDFa section of the HTML5 specification.
</p>
<h3>
Modifications to XHTML+RDFa
</h3>
<p>
<em>This section is normative.</em>
</p>
<p>
The [<a href="http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFa</a>]
Recommendation is the base document on which this section builds. That
document specifies the attributes and processing rules for extracting
RDF from an XHTML document. This section specifies changes to the
attributes and processing rules defined in XHTML+RDFa in order to
support extracting RDF from HTML documents.
</p>
<h4>Specifying the language for a literal</h4>
<p>
The <code>lang</code> attribute must be supported in the same manner
as the <code>xml:lang</code> attribute is in the XHTML+RDFa specification.
The precedence rules for selecting which value overrides the other is
outlined in the section titled "The lang and xml:lang attributes" in
the HTML5 specification.
</p>
<p>
If an author is unsure of the final encapsulating DOCTYPE for their
markup, such as HTML5 vs. XHTML5, it is suggested that the author specify
both <code>lang</code> and <code>xml:lang</code> where the value in
both attributes is exactly the same.
</p>
<h4>Invalid XMLLiteral values</h4>
<p>
When generating literals of type XMLLiteral, the processor must ensure that
the output XMLLiteral is
<a href="http://www.w3.org/TR/xml/#dt-wellformed">well-formed XML</a>.
If the input is not well-formed XML</a>, the processor must transform
the input text in a way that generates well-formed XML.
<span class="XXX">We need to specify the algorithm for doing so.</span>
</p>
<p>
Transformation to well-formed XML is required because an application
that consumes XMLLiteral data expects that data to be well-formed.
</p>
<p>
The transformation requirement does not apply to input data that are
text-only, such as literals that contain a <code>datatype</code> attribute
with an empty value (<code>""</code>), or input data that that contain
only text nodes.
</p>
<h4>The <code>xmlns:</code> attribute</h4>
<p class="XXX">
There have been various objections to the usage of the <code>xmlns</code>:
attribute across all HTML family languages. It is currently unknown whether
or not the <code>xmlns</code>: attribute will be supported in HTML5 as it
is defined in the
[<a href="http://www.w3.org/TR/REC-xml-names/">Namespaces in XML</a>]
specification. This section assumes deprecation of the <code>xmlns:</code>
attribute. The next section provides an alternate mechanism for
specifying prefix mappings in addition to deprecated use of
<code>xmlns:</code>.
</p>
<p>
If CURIE prefix name definitions are specified using <code>xmlns:</code>,
the definitions must be processed using the rules specified in the
[<a href="http://www.w3.org/TR/REC-xml-names/">Namespaces in XML</a>]
Recommendation.
</p>
<p>
If CURIE prefix name definitions are specified using <code>xmlns:</code>, and
since HTML attribute names are case-insensitive, CURIE prefix names declared
using the <code>xmlns:</code>attribute-name pattern
<code>xmlns:<PREFIX>="<URI>"</code> should be specified
using only lower-case characters. For example, the text "xmlns:" and the
text in "<PREFIX>" should be lower-case only. This is to ensure that
prefix mappings are interpreted in the same way between HTML
(case-insensitive attribute names) and XHTML (case-sensitive attribute
names) document types.
</p>
<h4>The <code>token</code> attribute</h4>
<p>
<div class="XXX">
Warning: All statements regarding the <code>token</code> attribute
do not enjoy consensus in the RDFa Task Force and could be removed at
any point without notice.
</div>
If authors would like to ensure that their prefix mappings are supported
across all XHTML and HTML documents, they should use the <code>token</code>
attribute to specify CURIE mapping values.
</p>
<p>
The syntax for the <code>token</code> attribute value is as follows:
<pre>
token_mappings := 1*(token_mapping *whitespace)
token_mapping := token *whitespace '=' *whitespace mapping
token := NCName ; as defined in [<a href="http://www.w3.org/TR/REC-xml-names/#NT-NCName">Namespaces in XML</a>]
mapping := irelative-ref ; as defined in [<a href="http://www.ietf.org/rfc/rfc3987">IRI</a>]
whitespace := White_Space ; as defined in the HTML5 Specification under '"White_Space" characters'
</pre>
For example, the following markup:
<pre>
<body token="ex=http://example.org/">
</pre>
when applied to the following HTML snippet:
<pre>
<a rel="ex:bar">
</pre>
would expand the CURIE value in <code>rel</code> as
<code>http://example.org/bar</code>. Similarly, for the following markup:
<pre>
<body token="author=http://example.org/author publisher=http://example.org/publisher">
</pre>
when applied to the following HTML snippet:
<pre>
<a rel="author">
</pre>
would expand the CURIE value in <code>rel</code> as <code>http://example.org/author</code>.
</p>
<h4>Use of URIs in CURIE-only attribute values</h4>
<p>
<div class="XXX">
Warning: All statements regarding the use of URIs in attribute value's
intended to receive reserved_words, CURIEs or Safe CURIEs, per the
XHTML+RDFa specification do not enjoy consensus in the RDFa Task Force
and could be removed at any point without notice.
</div>
<p>
<p>
Document authors should not create CURIE prefix mappings for well-known
URI schemes such as http, ftp, urn and a number of other well-known schemes
specified in
[<a href="http://www.iana.org/assignments/uri-schemes.html">The IANA URI Schemes Registry</a>],
as well as other URI schemes that are
commonly used on the Internet. If common URI schemes are used as CURIE
prefixes, then they may affect triple generation via modifications to the
CURIE processing algorithm (described below). The use of common URI schemes
as CURIE prefixes may result in unexpected substitutions in certain
markup scenarios.
</p>
<p>
CURIE processing must follow the processing definition specified in
the XHTML+RDFa Recommendation with the following modification:
</p>
<p>
If a prefix mapping is not found for text that is given to the CURIE
processing algorithm, and the text is an Internationalized Resource
Identifier as defined in
[<a href="http://www.ietf.org/rfc/rfc3987">IRI</a>], then the expanded
value of the potential CURIE should be the IRI.
</pre>
</p>
--- NEW FILE: rdfa-module.html ---
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</head>
<body>
<div class=head>
<p>
<a href=http://www.w3.org/><img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72></a>
</p>
<h1>HTML5+RDFa</h1>
<h2 class="no-num no-toc" id=a-mechanism-for-embedding-rdf-in-html>
A mechanism for embedding RDF in HTML
</h2>
<h2 class="no-num no-toc" id=editor-s-draft-date-1-january-1970>Editor's Draft 13 July 2009</h2>
<!--:ZZZ-->
<dl>
<!-- ZZZ: update the month/day (twice), (un)comment out
<dt>This Version:</dt>
<dd><a href="http://www.w3.org/TR/2009/WD-html5-20090423/">http://www.w3.org/TR/2009/WD-html5-20090423/</a></dd>
:ZZZ -->
<dt>
Latest Published Version:
</dt>
<dd>
Not published
</dd>
<dt>
Latest Editor's Draft:
</dt>
<dd>
<a href=http://dev.w3.org/public/source/html5/rdfa/rdfa-module.html>http://dev.w3.org/public/source/html5/rdfa/rdfa-module.html</a>
</dd><!-- ZZZ: add the new version after it has shipped -->
<dt>
Previous Versions:
</dt>
<dd>
None
</dd><!-- :ZZZ -->
<dt>
Contributors (alphabetical order):
</dt>
<dd>
Ben Adida (Chair, Creative Commons)
</dd>
<dd>
Mark Birbeck (Editor, RDFa Core and inventor of RDFa concept, Web
Backplane Ltd.)
</dd>
<dd>
Shane McCarron (Editor, RDFa Core, Applied Testing and Technology, Inc.)
</dd>
<dd>
Steven Pemberton (Chair, XHTML2, CWI)
</dd>
<dd>
<a href=mailto:msporny@digitalbazaar.com>Manu Sporny</a>, (Editor, HTML5+RDFa, Digital Bazaar, Inc.)
</dd>
</dl>
<p class=copyright>
<a href=http://www.w3.org/Consortium/Legal/ipr-notice#Copyright>Copyright</a> © 2009 <a href=http://www.w3.org/><abbr title="World Wide Web
Consortium">W3C</abbr></a><sup>®</sup> (<a href=http://www.csail.mit.edu/><abbr title="Massachusetts Institute of
Technology">MIT</abbr></a>, <a href=http://www.ercim.org/><abbr title="European Research Consortium for Informatics and
Mathematics">ERCIM</abbr></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>
</div>
<hr class=top>
<h2 class="no-num no-toc" id=abstract>
Abstract
</h2>
<p>
This specification defines rules and guidelines for adapting the RDF
in XHTML 1.1 specification (RDFa) for use in the HTML5 and XHTML5 members
of the HTML family. The rules defined in this document not only apply
to HTML5 documents, but also to HTML4 documents interpreted through the
HTML5 parsing rules.
</p>
<h2 class="no-num no-toc" id=status-of-this-document>
Status of this document
</h2><!-- intro boilerplate (required) -->
<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 most recently formally published 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>
If you wish to make comments regarding this document, please send them to
<a href=mailto:public-rdf-in-xhtml-tf@w3.org>public-rdf-in-xhtml-tf@w3.org</a>
(<a href="mailto:public-rdf-in-xhtml-tf-request@w3.org?subject=subscribe">subscribe</a>,
<a href=http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/>archives</a>)
</p>
<!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
<!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- stability (required) -->
<p>
Implementors should be aware that this specification is not stable.
<strong>Implementors who are not taking part in the discussions are likely
to find the specification changing out from under them in incompatible
ways.</strong> Vendors interested in implementing this specification
before it eventually reaches the Candidate Recommendation stage should
join the aforementioned mailing lists and take part in the discussions.
</p><!-- not everyone agrees with html5 (requested before fpwd) -->
<p>
The publication of this document by the W3C as a W3C Working Draft does
not imply that all of the participants in the W3C HTML working group
endorse the contents of the specification. Indeed, for any section of the
specification, one can usually find many members of the working group or
of the W3C as a whole who object strongly to the current text, the
existence of the section at all, or the idea that the working group should
even spend time discussing the concept of that section.
</p>
<!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) -->
<p>
The latest stable version of the editor's draft of this specification is
always available on <a href=http://dev.w3.org/html5/rdfa/rdfa-module.html>the W3C CVS server</a>.
The <a href=http://dev.w3.org/html5/rdfa/rdfa>latest editor's working copy</a> (which may contain unfinished text in the process of
being prepared) is also available.
</p>
<!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) -->
<p>
The W3C <a href=http://www.w3.org/html/wg/>HTML Working Group</a> is the
W3C working group responsible for this specification's progress along the
W3C Recommendation track.
</p>
<!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) -->
<p>
This specification is intended to be included in the HTML5 specification
as a section of the overall specification.
</p>
<!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate -->
<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/40318/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>
<h2 id=rdfa><span class=secno>1 </span>
<dfn>RDFa</dfn>
</h2>
<h3 id=issues><span class=secno>1.1 </span>
Issues
</h3>
<p class=XXX>
This section outlines a number of editorial issues with the RDFa
section of the HTML5 specification.
</p>
<p class=XXX>
In order to provide a module that can be authored, inserted and moved
easily within the HTML5 specification, the RDFa specification section is
being edited separately from the main HTML5 specification source file.
There are two documents that are generated from the RDFa specification
source. The first is the full HTML5 specification, which includes the
RDFa specification section. The second is the stand-alone HTML5+RDFa
document.
</p>
<p class=XXX>
The upside to having two documents generated from the same source mainly
has to do with load-times for the HTML5 specification in web browsers.
Loading the 4MB HTML5 specification can be very slow, even in Firefox
3.5 or Chrome. So for those that want to just look at the RDFa specification
text, there is a much smaller, separate document for that purpose.
</p>
<p class=XXX>
Unfortunately, there are a number of down-sides with this approach. The
first is that the specification language becomes more verbose. The second
is that cross-references within the HTML5 document are impossible due to
a bug/feature in the Anolis specification processor.
</p><p class=XXX>
These down-sides are not ideal and will eventually be remedied as we find
a way to either fix Anolis or integrate the RDFa document into the HTML5
specification.
</p>
<h3 id=introduction><span class=secno>1.2 </span>
Introduction
</h3>
<p>
<em>This section is informative.</em>
</p>
<p>
Starting in 2006, the Semantic Web Deployment Work Group
began work to develop a technology to express semantic data in
XHTML 1.1. This technology was successfully developed and is now
called RDFa (The Resource Description Framework in Attributes).
While HTML provides a mechanism to express the structure of a document
(title, paragraphs, links), RDFa provides a mechanism to express
the meaning of a document (people, places, events).
</p><p>
</p><p>
The document, titled "RDFa in XHTML: Syntax and Processing Rules"
[<a href=http://www.w3.org/TR/rdfa-syntax/>XHTML+RDFa</a>], defined
a set of attributes and rules for processing those attributes that
resulted in the output of machine-readable semantic data. While the
document was specific to the XHTML 1.1 member in the HTML family, the
attributes and rules were always intended to operate across any
tree-based structure containing attributes on tree nodes (such as HTML4,
SVG and ODF).
</p>
<p>
While RDFa was initially specified for use in XHTML 1.1, adoption by
a number of large organizations on the Web spurred RDFa's use in non-XHTML
languages. Its use in HTML4 and HTML5, before an official specification
was developed for those languages, caused concern regarding document
conformance.
</p>
<p>
Over the years, the members of the RDFa Task Force
[<a href=http://rdfa.info/>RDFaTF</a>] had discussed the possibility
of applying the same attributes and processing rules outlined in the
XHTML+RDFa specification to all HTML family documents. By design, the
possibility of a unified semantic data expression mechanism between all
HTML and XHTML family documents was squarely in the realm of possibility.
</p>
<p>
This section describes the modifications to the original XHTML+RDFa
specification that permit the use of RDFa in all HTML family documents.
By using the attributes and processing rules described in the
XHTML+RDFa specification and heeding the minor changes in this
section, authors can expect to generate markup that produces the same
semantic data output in HTML4, HTML5 and XHTML5.
</p>
<p>
This section has been prepared by Manu Sporny (President/CEO of Digital
Bazaar, Inc.) in consultation with key members of the
RDFa in XHTML Task Force, the HTML WG, the WHAT WG, and other
interested parties.
</p>
<h3 id=parsing-model><span class=secno>1.3 </span>
Parsing Model
</h3>
<p>
Section 5 of the
[<a href=http://www.w3.org/TR/rdfa-syntax/>XHTML+RDFa</a>] specification
defines a generic processing model for extracting RDF from a
tree-based model. The method of transforming an input document into a
model suited for the RDFa processing rules is intentionally not defined
in the XHTML+RDFa specification. The method of transformation was intended
to be defined in the implementation language, in this case, this section of
the HTML5 specification.
</p>
<p>
In the context of the HTML5 specification, the parsing rules for an input
document in HTML4 and HTML5 are clearly defined. The processing model
defined in Section 5 of the XHTML+RDFa specification should be executed
on the HTML5 DOM. While the HTML5 DOM is not currently stable, a parsing
mechanism built on top of the html5lib library should provide a
mechanism that is guaranteed to eventually provide a stable, tree-based
model for the RDFa processing rules.
</p>
<p>
RDFa's tree-based processing rules enable an input document to be
automatically corrected, cleaned-up, re-arranged, or modified in any
way that is approved by the host language. For example, element nesting
issues in HTML documents may be corrected before the input document is
serialized into the tree-based model on which the RDFa processing rules
will operate.
</p>
<h3 id=conformance-requirements><span class=secno>1.4 </span>
Conformance Requirements
</h3>
<p>
<em>This section is normative.</em>
</p>
<p>
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [<a class=nref href=#ref_RFC2119>RFC2119</a>].
</p>
<p>
Note that all examples in this document are informative, and are not meant
to be interpreted as normative requirements.
</p>
<h3 id=document-conformance><span class=secno>1.5 </span>
Document Conformance
</h3>
<p>
In order for a document to claim that it is a conforming HTML+RDFa document,
it must provide the facilities described as mandatory in this section.
The document conformance criteria are listed below, of which only a subset
are mandatory:
</p>
<ol>
<li>
There should be a DOCTYPE declaration specified prior to the root element
in the document that follows the conventions outlined in the
"The DOCTYPE section" of the HTML5 specification.
</li>
<li>
The root element of the document must follow the conventions outlined
in "The root element" section of the HTML5 specification.
</li>
<li>
There may be a <code>link</code> element contained in the
<code>head</code> element that contains <code>profile</code> for
the the <code>rel</code> attribute and
<code>http://www.w3.org/1999/xhtml/vocab</code> for the <code>href</code>
attribute.
<div class=XXX>
This requires the HTML5 spec to add <code>profile</code> to the list of
allow-able <code>rel</code>-values. This is used as the signalling
mechansim for an RDFa document because the <code>profile</code>
attribute is deprecated in HTML5.
</div>
</li>
</ol>
<h3 id=user-agent-conformance><span class=secno>1.6 </span>
User Agent Conformance
</h3>
<p>
A conforming RDFa user agent must:
</p><ul>
<li>
Conform to all conformance requirements listed in the
"Conformance requirements" section of the HTML5 specification.
</li>
<li>
Implement all of the features required in the RDFa section of the
HTML5 specification.
</li>
<li>
Implement all of the features specified in the XHTML+RDFa specification,
excluding those features which are specifically overridden by the RDFa
section of the HTML5 specification.
</li>
</ul>
<p></p>
<h3 id=rdfa-processor-conformance><span class=secno>1.7 </span>
RDFa Processor Conformance
</h3>
<p>
A conforming RDFa Processor must implement all of the mandatory features
specified in the XHTML+RDFa specification. It must also support any
mandatory features specified in the RDFa section of the HTML5 specification.
</p>
<h3 id=modifications-to-xhtml-rdfa><span class=secno>1.8 </span>
Modifications to XHTML+RDFa
</h3>
<p>
<em>This section is normative.</em>
</p>
<p>
The [<a href=http://www.w3.org/TR/rdfa-syntax/>XHTML+RDFa</a>]
Recommendation is the base document on which this section builds. That
document specifies the attributes and processing rules for extracting
RDF from an XHTML document. This section specifies changes to the
attributes and processing rules defined in XHTML+RDFa in order to
support extracting RDF from HTML documents.
</p>
<h4 id=specifying-the-language-for-a-literal><span class=secno>1.8.1 </span>Specifying the language for a literal</h4>
<p>
The <code>lang</code> attribute must be supported in the same manner
as the <code>xml:lang</code> attribute is in the XHTML+RDFa specification.
The precedence rules for selecting which value overrides the other is
outlined in the section titled "The lang and xml:lang attributes" in
the HTML5 specification.
</p>
<p>
If an author is unsure of the final encapsulating DOCTYPE for their
markup, such as HTML5 vs. XHTML5, it is suggested that the author specify
both <code>lang</code> and <code>xml:lang</code> where the value in
both attributes is exactly the same.
</p>
<h4 id=invalid-xmlliteral-values><span class=secno>1.8.2 </span>Invalid XMLLiteral values</h4>
<p>
When generating literals of type XMLLiteral, the processor must ensure that
the output XMLLiteral is
<a href=http://www.w3.org/TR/xml/#dt-wellformed>well-formed XML</a>.
If the input is not well-formed XML, the processor must transform
the input text in a way that generates well-formed XML.
<span class=XXX>We need to specify the algorithm for doing so.</span>
</p>
<p>
Transformation to well-formed XML is required because an application
that consumes XMLLiteral data expects that data to be well-formed.
</p>
<p>
The transformation requirement does not apply to input data that are
text-only, such as literals that contain a <code>datatype</code> attribute
with an empty value (<code>""</code>), or input data that that contain
only text nodes.
</p>
<h4 id=the-xmlns:-attribute><span class=secno>1.8.3 </span>The <code>xmlns:</code> attribute</h4>
<p class=XXX>
There have been various objections to the usage of the <code>xmlns</code>:
attribute across all HTML family languages. It is currently unknown whether
or not the <code>xmlns</code>: attribute will be supported in HTML5 as it
is defined in the
[<a href=http://www.w3.org/TR/REC-xml-names/>Namespaces in XML</a>]
specification. This section assumes deprecation of the <code>xmlns:</code>
attribute. The next section provides an alternate mechanism for
specifying prefix mappings in addition to deprecated use of
<code>xmlns:</code>.
</p>
<p>
If CURIE prefix name definitions are specified using <code>xmlns:</code>,
the definitions must be processed using the rules specified in the
[<a href=http://www.w3.org/TR/REC-xml-names/>Namespaces in XML</a>]
Recommendation.
</p>
<p>
If CURIE prefix name definitions are specified using <code>xmlns:</code>, and
since HTML attribute names are case-insensitive, CURIE prefix names declared
using the <code>xmlns:</code>attribute-name pattern
<code>xmlns:<PREFIX>="<URI>"</code> should be specified
using only lower-case characters. For example, the text "xmlns:" and the
text in "<PREFIX>" should be lower-case only. This is to ensure that
prefix mappings are interpreted in the same way between HTML
(case-insensitive attribute names) and XHTML (case-sensitive attribute
names) document types.
</p>
<h4 id=the-token-attribute><span class=secno>1.8.4 </span>The <code>token</code> attribute</h4>
<p>
</p><div class=XXX>
Warning: All statements regarding the <code>token</code> attribute
do not enjoy consensus in the RDFa Task Force and could be removed at
any point without notice.
</div>
If authors would like to ensure that their prefix mappings are supported
across all XHTML and HTML documents, they should use the <code>token</code>
attribute to specify CURIE mapping values.
<p></p>
<p>
The syntax for the <code>token</code> attribute value is as follows:
</p><pre> token_mappings := 1*(token_mapping *whitespace)
token_mapping := token *whitespace '=' *whitespace mapping
token := NCName ; as defined in [<a href=http://www.w3.org/TR/REC-xml-names/#NT-NCName>Namespaces in XML</a>]
mapping := irelative-ref ; as defined in [<a href=http://www.ietf.org/rfc/rfc3987>IRI</a>]
whitespace := White_Space ; as defined in the HTML5 Specification under '"White_Space" characters'
</pre>
For example, the following markup:
<pre> <body token="ex=http://example.org/">
</pre>
when applied to the following HTML snippet:
<pre> <a rel="ex:bar">
</pre>
would expand the CURIE value in <code>rel</code> as
<code>http://example.org/bar</code>. Similarly, for the following markup:
<pre> <body token="author=http://example.org/author publisher=http://example.org/publisher">
</pre>
when applied to the following HTML snippet:
<pre> <a rel="author">
</pre>
would expand the CURIE value in <code>rel</code> as <code>http://example.org/author</code>.
<p></p>
<h4 id=use-of-uris-in-curie-only-attribute-values><span class=secno>1.8.5 </span>Use of URIs in CURIE-only attribute values</h4>
<p>
</p><div class=XXX>
Warning: All statements regarding the use of URIs in attribute value's
intended to receive reserved_words, CURIEs or Safe CURIEs, per the
XHTML+RDFa specification do not enjoy consensus in the RDFa Task Force
and could be removed at any point without notice.
</div>
<p>
</p><p>
Document authors should not create CURIE prefix mappings for well-known
URI schemes such as http, ftp, urn and a number of other well-known schemes
specified in
[<a href=http://www.iana.org/assignments/uri-schemes.html>The IANA URI Schemes Registry</a>],
as well as other URI schemes that are
commonly used on the Internet. If common URI schemes are used as CURIE
prefixes, then they may affect triple generation via modifications to the
CURIE processing algorithm (described below). The use of common URI schemes
as CURIE prefixes may result in unexpected substitutions in certain
markup scenarios.
</p>
<p>
CURIE processing must follow the processing definition specified in
the XHTML+RDFa Recommendation with the following modification:
</p>
<p>
If a prefix mapping is not found for text that is given to the CURIE
processing algorithm, and the text is an Internationalized Resource
Identifier as defined in
[<a href=http://www.ietf.org/rfc/rfc3987>IRI</a>], then the expanded
value of the potential CURIE should be the IRI.
</p>
</body></html>
Received on Sunday, 12 July 2009 18:36:10 UTC