RDFa in XHTML: Syntax and Processing

 A collection of attributes and processing rules for extending XHTML
to support RDF

 W3C Recommendation 14 October 2008


This version:

http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014

Latest version:

http://www.w3.org/TR/rdfa-syntax

Previous version:

http://www.w3.org/TR/2008/PR-rdfa-syntax-20080904

Diff from previous version:

rdfa-syntax-diff.html


Editors:

Ben Adida, Creative Commons  ben@adida.net

Mark Birbeck, webBackplane mark.birbeck@webBackplane.com

Shane McCarron, Applied Testing and Technology, Inc. shane@aptest.com

Steven Pemberton, CWI


Please refer to the errata for this document, which may include some
normative corrections.

This document is also available in these non-normative formats:
PostScript version, PDF version, ZIP
archive, and Gzip'd TAR archive.

The English version of this specification is the only normative
version. Non-normative translations may also be available.

Copyright © 2007-2008 
W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability,
trademark and document use rules apply.



 Abstract

The current Web is primarily made up of an enormous number of
documents that have been created using HTML. These documents contain
significant amounts of structured data, which is largely
unavailable to tools and applications. When publishers can express
this data more completely, and when tools can read it, a new world of
user functionality becomes available, letting users transfer
structured data between applications and web sites, and allowing
browsing applications to improve the user experience: an event on a
web page can be directly imported into a user's desktop calendar;
a license on a document can be detected so that users can be informed
of their rights automatically; a photo's creator, camera setting
information, resolution, location and topic can be published as
easily as the original photo itself, enabling structured search and
sharing.

RDFa is a specification for attributes to express structured data in
any markup language. This document specifies how to use RDFa with
XHTML. The rendered, hypertext data of XHTML is reused by the
RDFa markup, so that publishers don't need to repeat significant data
in the document content. The underlying abstract representation is RDF
[RDF-PRIMER],
which lets publishers build their own vocabulary, extend others, and
evolve their vocabulary with maximal interoperability over time. The
expressed structure is closely tied to the data, so that
rendered data can be copied and pasted along with its relevant
structure.

The rules for interpreting the data are generic, so that there is no
need for different rules for different formats; this allows authors
and publishers of data to define their own formats without
having to update software, register formats via a central authority,
or worry that two formats may interfere with each other.

RDFa shares some use cases with microformats [MICROFORMATS]. Whereas
microformats specify both a syntax for embedding structured data into
HTML
documents and a vocabulary of specific terms for each microformat,
RDFa specifies only a syntax and relies on independent specification
of terms (often called vocabularies or taxonomies) by others.
RDFa allows terms from multiple independently-developed vocabularies
to be freely intermixed and is designed such that the language can be
parsed without knowledge of the specific term vocabulary
being used.

This document is a detailed syntax specification for RDFa, aimed at:


those looking to create an RDFa parser, and who therefore need a
detailed description of the parsing rules;

those looking to recommend the use of RDFa within their organisation,
and who would like to create some guidelines for their users;

anyone familiar with RDF, and who wants to understand more about what
is happening 'under the hood', when an RDFa parser runs.


 For those looking for an introduction to the use of RDFa and some
real-world examples, please consult the RDFa Primer.

 How to Read this Document

If you are already familiar with RDFa, and you want to examine the
processing rules — perhaps to create a parser — then
you'll find the Processing Model section
of most interest. It contains an overview of each of the processing
steps, followed by more detailed sections, one for each rule.

If you are not familiar with RDFa, but you are familiar with RDF, then
you might find reading the Syntax Overview useful, before looking at
the Processing Model since it gives a range of examples of XHTML
mark-up that use RDFa. Seeing some examples first should make reading
the processing rules easier.

If you are not familiar with RDF, then you might want to take a look
at the section on RDF Terminology before trying to do too much with
RDFa. Although RDFa is
designed to be easy to author—and authors don't need to
understand RDF to use it—anyone writing applications that
consume RDFa will need to understand RDF. There is a lot of
material about RDF on the web, and a growing range of tools that
support RDFa, so all we try to do in this document is provide enough
background on RDF to make the goals of RDFa clearer.

And finally, if you are not familiar with either RDFa or RDF, and
simply want to add RDFa to your documents, then you may find the RDFa
Primer [RDFaPRIMER] to be a better introduction.

 Status of this Document

This section describes the status of this document at the time of its
publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of
this technical report can be found in the W3C technical reports index
at http://www.w3.org/TR/.

This document has been reviewed by W3C Members, by software
developers, and by other W3C groups and interested parties, and is
endorsed by the Director as a W3C Recommendation. It is a stable
document and may be used as reference material or cited from another
document. W3C's role in making the Recommendation is to draw attention
to the specification and to promote its widespread
deployment. This enhances the functionality and interoperability of
the Web.

Members of the public are invited to send comments on this
Recommendation to public-rdf-in-xhtml-tf@w3.org (with public archive).

A sample test harness is available. This set of tests is not intended
to be exhaustive. Users may find the tests to be useful
examples of RDFa usage. An implementation report lists several
implementations of this specification tested during the
Candidate Recommendation period. A community-maintained Wiki page
includes subsequent updates.

This document has been produced jointly by the Semantic Web Deployment
Working Group and the XHTML2 Working
Group as part of the Semantic Web Activity and the HTML Activity. It
contains small editorial changes
arising from comments received during the Proposed Recommendation
review; see the diff-marked version for details.

This document was produced by groups operating under the 5 February
2004 W3C Patent Policy. W3C maintains a public list of any patent
disclosures made in connection with the deliverables of the XHTML 2
Working Group; and also maintains a public list of any patent
disclosures made in connection with the deliverables of the Semantic
Web Deployment Working Group;
those pages also include instructions for disclosing a patent. An
individual who has actual knowledge of a patent which the individual
believes contains Essential Claim(s) must disclose the information in
accordance with section 6 of the W3C Patent Policy.

 Table of Contents



1. Motivation

2. Syntax Overview 


2.1. The RDFa Attributes

2.2. Examples



3. RDF Terminology 


3.1. Statements

3.2. Triples

3.3. URI references

3.4. Plain literals

3.5. Typed literals

3.6. Turtle

3.7. Graphs

3.8. Compact URIs

3.9. XHTML Fragments and RDFa

3.10. A description of RDFa in RDF terms



4. Conformance Requirements 


4.1. Document Conformance

4.2. User Agent Conformance

4.3. RDFa Processor Conformance



5. Processing Model 


5.1. Overview

5.2. Evaluation Context

5.3. Chaining

5.4. CURIE and URI Processing 


5.4.1. Scoping of Prefix Mappings

5.4.2. Converting a CURIE to a URI

5.4.3. General Use of CURIEs in Attributes

5.4.4. Use of CURIEs in Specific Attributes

5.4.5. Referencing Blank Nodes



5.5. Sequence



6. RDFa Processing in detail 


6.1. Changing the evaluation context 


6.1.1. Setting the current subject



6.2. Completing 'incomplete triples'

6.3. Object resolution 


6.3.1. Literal object resolution

6.3.2. URI object resolution





7. CURIE Syntax Definition

8. XHTML+RDFa Definition

9. Metainformation Attributes Module 


9.1. Datatypes

9.2. Metainformation Attributes Collection

9.3. @rel/@rev attribute values



A. XHTML+RDFa DTD 


A.1. XHTML Metainformation Attributes Module

A.2. XHTML+RDFa Content Model Module

A.3. XHTML+RDFa Driver Module

A.4. SGML Open Catalog Entry for XHTML+RDFa



B. CURIE Datatypes 


B.1. XML Schema Definition

B.2. XML DTD Definition



C. Deployment Advice

D. References 


D.1. Related Specifications

D.2. Other References



E. Change History

F. Acknowledgments




1. Motivation

This section is informative.

RDF/XML [RDF-SYNTAX] provides sufficient flexibility to represent all
of the abstract concepts in RDF [RDF-CONCEPTS]. However, it presents a
number of challenges; first it is difficult or impossible to validate
documents that contain RDF/XML using XML Schemas or DTDs, which
therefore makes it difficult to import RDF/XML into other markup
languages. Whilst newer schema languages such as RELAX NG [RELAXNG] do
provide a way to
validate documents that contain arbitrary RDF/XML, it will be a while
before they gain wide support.

Second, even if one could add RDF/XML directly into an XML dialect
like XHTML, there would be significant data duplication between the
rendered data and the RDF/XML structured data. It would be
far better to add RDF to a document without repeating the document's
existing data. For example, an XHTML document that explicitly renders
its author's name in the text—perhaps as a byline on a
news site—should not need to repeat this name for the RDF
expression of the same concept: it should be possible to supplement
the existing markup in such a way that it can also be interpreted
as RDF.

Another reason for aligning the rendered data with the structured data
is that it is highly beneficial to express the web data's structure
'in context'; as users often want to transfer structured
data from one application to another, sometimes to or from a
non-web-based application, the user experience can be enhanced. For
example, information about specific rendered data could be presented
to the user via 'right-clicks' on an item of interest.

In the past, many attributes were 'hard-wired' directly into the
markup language to represent specific concepts. For example, in XHTML
1.1 [XHTML11] and
HTML [HTML4] there is @cite; the attribute allows an author to add
information to a document which is used to indicate the origin of a
quote.

However, these 'hard-wired' attributes make it difficult to define a
generic process for extracting metadata from any document since a
parser would need to know about each of the special
attributes. One motivation for RDFa has been to devise a means by
which documents can be augmented with metadata in a general rather
than hard-wired manner. This has been achieved by creating a fixed
set of attributes and parsing rules, but allowing those attributes to
contain properties from any of a number of the growing range of
available RDF vocabularies. The values of those
properties are in most cases the information that is already in an
author's XHTML document.

RDFa alleviates the pressure on XML format authors to anticipate all
the structural requirements users of their format might have, by
outlining a new syntax for RDF that relies only on XML
attributes. This specification deals specifically with the use of RDFa
in XHTML, and defines an RDF mapping for a number of XHTML attributes,
but RDFa can be easily imported into other XML-based
markup languages.


2. Syntax Overview

This section is informative.

The following examples are intended to help readers who are not
familiar with RDFa to quickly get a sense of how it works. For a more
thorough introduction, please read the RDFa Primer [RDFaPRIMER].

For brevity, in the following examples and throughout this document,
assume that the following vocabulary prefixes have been defined:



biblio:
http://example.org/biblio/0.1



cc:
http://creativecommons.org/ns#



dbp:
http://dbpedia.org/property/



dbr:
http://dbpedia.org/resource/



dc:
http://purl.org/dc/elements/1.1/



ex:
http://example.org/



foaf:
http://xmlns.com/foaf/0.1/



rdf:
http://www.w3.org/1999/02/22-rdf-syntax-ns#



rdfs:
http://www.w3.org/2000/01/rdf-schema#



taxo:
http://purl.org/rss/1.0/modules/taxonomy/



xhv:
http://www.w3.org/1999/xhtml/vocab#



xsd:
http://www.w3.org/2001/XMLSchema#



2.1. The RDFa Attributes

RDFa in XHTML makes use of a number of XHTML attributes, as well as
providing a few new ones. Attributes that already exist in XHTML will
have the same meaning as in XHTML, although their syntax
may be slightly modified. For example, in XHTML, @rel already defines
the relationship between one document and another. However, in XHTML
there is no clear way to add new
values; RDFa sets out to explicitly solve this problem, and does so by
allowing URIs as values. It also introduces the idea of 'compact
URIs'—referred to as CURIEs in this document—which
allow a full URI value to be expressed succinctly.

The XHTML attributes that are relevant are:


@rel

a whitespace separated list of CURIEs, used for expressing
relationships between two resources ('predicates' in RDF terminology);

@rev

a whitespace separated list of CURIEs, used for expressing reverse
relationships between two resources (also 'predicates');

@content

a string, for supplying machine-readable content for a literal (a
'plain literal object', in RDF terminology);

@href

a URI for expressing the partner resource of a relationship (a
'resource object', in
RDF terminology);

@src

a URI for expressing the partner resource of a relationship when the
resource is
embedded (also a 'resource object').


The new—RDFa-specific—attributes are:


@about

a URIorSafeCURIE, used for stating what the data is about (a 'subject'
in RDF terminology);

@property

a whitespace separated list of CURIEs, used for expressing
relationships between a subject and some literal text (also a
'predicate');

@resource

a URIorSafeCURIE for expressing the partner resource of a relationship
that is not intended to be 'clickable' (also an
'object');

@datatype

a CURIE representing a datatype, to express the datatype of a literal;

@typeof

a whitespace separated list of CURIEs that indicate the RDF type(s) to
associate with a subject.


For a normative definition of these attributes see the XHTML
Metainformation Attributes Module.

2.2. Examples

As an XHTML author you will already be familiar with using meta and
link to add additional information to your documents:



<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>Page 7</title>
    <meta name="author" content="Mark Birbeck" />
    <link rel="prev" href="page6.html" />
    <link rel="next" href="page8.html" />
  </head>
  <body>...</body>
</html>



RDFa makes use of this concept, enhancing it with the ability to make
use of other vocabularies by using compact URIs:



<html
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:foaf="http://xmlns.com/foaf/0.1/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  >
  <head>
    <title>My home-page</title>
    <meta property="dc:creator" content="Mark Birbeck" />
    <link rel="foaf:topic" href="http://www.formsPlayer.com/#us"
/>
  </head>
  <body>...</body>
</html>



Although not widely used, XHTML already supports the use of @rel and
@rev on the a element. This becomes more useful in RDFa with
the addition of support for different vocabularies:



This document is licensed under a 
<a xmlns:cc="http://creativecommons.org/ns#"
  rel="cc:license"
  href="http://creativecommons.org/licenses/by-nc-nd/3.0/">
  Creative Commons License
</a>.



Not only can URLs in the document be re-used to provide metadata, but
so can inline text:



<html
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:cal="http://www.w3.org/2002/12/cal/ical#"
  >
  <head><title>Jo's Friends and Family
Blog</title></head>
  <body>
    <p>
      I'm holding
      <span property="cal:summary">
        one last summer Barbecue
      </span>,
      on September 16th at 4pm.
    </p>
  </body>
</html>



If some displayed text is different to the actual 'value' it
represents, more precise values can be added, which can optionally
include datatypes:



<html
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:cal="http://www.w3.org/2002/12/cal/ical#"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  >
  <head><title>Jo's Friends and Family
Blog</title></head>
  <body>
    <p>
      I'm holding
      <span property="cal:summary">
        one last summer Barbecue
      </span>,
      on
      <span property="cal:dtstart"
content="2007-09-16T16:00:00-05:00"
            datatype="xsd:dateTime">
        September 16th at 4pm
      </span>.
    </p>
  </body>
</html>



In many cases a block of mark-up will contain a number of properties
that relate to the same item; it's possible with RDFa to indicate the
type of that item:



<html
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:cal="http://www.w3.org/2002/12/cal/ical#"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  >
  <head><title>Jo's Friends and Family
Blog</title></head>
  <body>
    <p typeof="cal:Vevent">
      I'm holding
      <span property="cal:summary">
        one last summer Barbecue
      </span>,
      on
      <span property="cal:dtstart"
content="2007-09-16T16:00:00-05:00" 
            datatype="xsd:dateTime">
        September 16th at 4pm
      </span>.
    </p>
  </body>
</html>



The metadata features available in XHTML only allow information to be
expressed about the document itself. RDFa allows the document to
contain metadata information about other documents and
resources:



<html
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:biblio="http://example.org/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  >
  <head>
    <title>Books by Marco Pierre White</title>
  </head>
  <body>
    I think White's book
    '<span about="urn:ISBN:0091808189" typeof="biblio:book"
           property="dc:title">
      Canteen Cuisine
    </span>'
    is well worth getting since although it's quite advanced stuff, he
    makes it pretty easy to follow. You might also like
    <span about="urn:ISBN:1596913614" typeof="biblio:book"
          property="dc:description">
      White's autobiography
    </span>.
  </body>
</html>




3. RDF Terminology

This section is informative.

 The previous section gave examples of typical mark-up in order to
illustrate what RDFa in XHTML looks like. But what RDFa in XHTML
represents is RDF. In order to author RDFa in XHTML you
do not need to understand RDF, although it would certainly help.
However, if you are building a system that consumes the RDF output of
an RDFa in XHTML document you will almost certainly need to
understand RDF. In this section we introduce the basic concepts and
terminology of RDF. For a more thorough explanation of RDF, please
refer to the RDF Concepts document [RDF-CONCEPTS] and the RDF Sytax
Document [RDF-SYNTAX].

3.1. Statements

 The structured data that RDFa provides access to is a collection of
statements. A statement is a basic unit of information that has been
constructed in a specific format to make it
easier to process. In turn, by breaking large sets of information down
into a collection of statements, even very complex metadata can be
processed using simple rules.

 To illustrate, suppose we have the following set of facts:



Albert was born on March 14, 1879, in Germany. There is a picture of
him at
the web address,
http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.



This would be quite difficult for a machine to interpret, and it is
certainly not in a format that could be passed from one data
application to another. However, if we convert the information to a
set of statements it begins to be more manageable. The same
information could therefore be represented by the following shorter
'statements':



Albert was born on March 14, 1879.
Albert was born in Germany.
Albert has a picture at
  http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.



3.2. Triples

 To make this information machine-processable, RDF defines a structure
for these statements. A statement is formally called a [triple],
meaning
that it is made up of three components. The first is the subject of
the triple, and is what we are making our statements about. In all of
these examples the subject is 'Albert'.

 The second part of a triple is the property of the subject that we
want to define. In the examples here, the properties would be 'was
born on', 'was born in', and 'has a picture at'. These are
more usually called predicates in RDF.

 The final part of a triple is called the object. In the examples here
the three objects have the values 'March 14, 1879', 'Germany', and
'http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg'.

3.3. URI references

 Breaking complex information into manageable units helps us be
specific about our data, but there is still some ambiguity. For
example, which 'Albert' are we talking about? If another system has
more facts about 'Albert', how could we know whether they are about
the same person, and so add them to the list of things we know about
that person? If we wanted to find people born in Germany, how
could we know that the predicate 'was born in' has the same purpose as
the predicate 'birthplace' that might exist in some other system? RDF
solves this problem by replacing our vague terms with 
URI references.

 URIs are most commonly used to identify web pages, but RDF makes use
of them as a way to provide unique identifiers for concepts. For
example, we could identify the subject of all of our
statements (the first part of each triple) by using the DBPedia
[http://dbpedia.org] URI for Albert Einstein, instead of the ambiguous
string 'Albert':



<http://dbpedia.org/resource/Albert_Einstein>
   has the name 
   Albert Einstein.
<http://dbpedia.org/resource/Albert_Einstein>
   was born on 
   March 14, 1879.
<http://dbpedia.org/resource/Albert_Einstein>
   was born in 
   Germany.
<http://dbpedia.org/resource/Albert_Einstein>
   has a picture at
   http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg.



 URI references are also used to uniquely identify the objects in
metadata statements (the third part of each triple). The picture of
Einstein is already a URI, but we could also use a URI to
uniquely identify the country Germany. At the same time we'll indicate
that the name and date of birth really are literals (and not URIs), by
putting quotes around them:



<http://dbpedia.org/resource/Albert_Einstein> 
   has the name 
   "Albert Einstein".
<http://dbpedia.org/resource/Albert_Einstein> 
   was born on 
   "March 14, 1879".
<http://dbpedia.org/resource/Albert_Einstein> 
   was born in 
   <http://dbpedia.org/resource/Germany>.
<http://dbpedia.org/resource/Albert_Einstein> 
   has a picture at
  
<http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg>.



 URI references are also used to ensure that predicates are
unambiguous; now we can be sure that 'birthplace', 'place of birth',
'Lieu de naissance' and so on, all mean the same thing:



<http://dbpedia.org/resource/Albert_Einstein>
  <http://xmlns.com/foaf/0.1/name>
  "Albert Einstein".
<http://dbpedia.org/resource/Albert_Einstein>
  <http://dbpedia.org/property/dateOfBirth>
  "March 14, 1879".
<http://dbpedia.org/resource/Albert_Einstein>
  <http://dbpedia.org/property/birthPlace>
  <http://dbpedia.org/resource/Germany>.
<http://dbpedia.org/resource/Albert_Einstein>
  <http://xmlns.com/foaf/0.1/depiction>
  <http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg>.



3.4. Plain literals

 Although URI resources are always used for subjects and predicates,
the object part of a triple can be either a URI or a [literal]. In the
example triples, Einstein's name is represented by a [plain literal],
which means that it is a basic string with no type or language
information:



<http://dbpedia.org/resource/Albert_Einstein>
  <http://xmlns.com/foaf/0.1/name> "Albert Einstein".



3.5. Typed literals

 Some literals, such as dates and numbers, have very specific
meanings, so RDF provides a mechanism for indicating the type of a
literal. A [typed
literal] is indicated by attaching a URI to the end of a [plain
literal], and this URI indicates the literal's datatype. This URI is
usually
based on datatypes defined in the XML Schema Datatypes specification
[XMLSCHEMA]. The following syntax would be used to unambiguously
express Einstein's date
of birth as a literal of type http://www.w3.org/2001/XMLSchema#date:



<http://dbpedia.org/resource/Albert_Einstein>
  <http://dbpedia.org/property/dateOfBirth>
"1879-03-14"^^<http://www.w3.org/2001/XMLSchema#date>.



3.6. Turtle

 RDF itself does not have one set way to express triples, since the
key ideas of RDF are the triple and the use of URIs, and not any
particular syntax. However, there are a number of
mechanisms for expressing triples, such as RDF/XML, Turtle [TURTLE],
and of course RDFa. Many discussions of RDF make use of the Turtle
syntax to
explain their ideas, since it is quite compact. The examples we have
just seen are already using this syntax, and we'll continue to use it
throughout this document when we need to talk about the RDF
that could be generated from some RDFa. Turtle allows long URIs to be
abbreviated by using a URI mapping, which can be used to express a
compact URI as follows:



@prefix dbp: <http://dbpedia.org/property/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
<http://dbpedia.org/resource/Albert_Einstein>
  foaf:name "Albert Einstein" .
<http://dbpedia.org/resource/Albert_Einstein>
  dbp:birthPlace <http://dbpedia.org/resource/Germany> .



Here 'dbp:' has been mapped to the URI for DBPedia and 'foaf:' has
been mapped to the URI for the 'Friend of a Friend' taxonomy.

Any URI in Turtle could be abbreviated in this way. This means that we
could also have used the same technique to abbreviate the identifier
for Einstein, as well as the datatype indicator:



@prefix dbp: <http://dbpedia.org/property/> .
@prefix dbr: <http://dbpedia.org/resource/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
dbr:Albert_Einstein dbp:dateOfBirth "1879-03-14"^^xsd:date .
dbr:Albert_Einstein
  foaf:depiction
<http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg> .



 When writing examples, you will often see the following URI in the
Turtle representation:



<>



 This indicates the 'current document', i.e., the document being
processed. In reality there would always be a full URI based on the
document's location, but this abbreviation serves to make
examples more compact. Note in particular that the whole technique of
abbreviation is merely a way to make examples more compact, and the
actual triples generated would always use the full URIs.

3.7. Graphs

 A collection of triples is called a graph.

 For more information on the concepts described above, see
[RDF-CONCEPTS]. RDFa additionally defines the following terms:

3.8. Compact URIs

In order to allow for the compact expression of RDF statements, RDFa
allows the contraction of all [URI reference]s into a form called a
'compact URI',
or CURIE. A detailed discussion of this mechanism is in section CURIE
and URI Processing.

Note that CURIEs are only used in the mark-up and Turtle examples, and
will never appear in the generated [triple]s, which are defined in RDF
to use [URI reference]s.

Full details on how CURIEs are processed is in the section titled
CURIE Processing.

3.9. XHTML Fragments and RDFa

A growing use of embedded metadata is to take fragments of mark-up and
move them from one document to another. This may happen through the
use of tools, such as drag-and-drop in a browser, or
through snippets of code provided to authors for inclusion in their
documents. (A good example of the latter is the licensing fragment
provided by Creative Commons.)

However, those involved in creating fragments (either by building
tools, or authoring snippets), should be aware that this specification
does not say how fragments of XHTML+RDFa should be
processed whilst they are 'outside' of a complete XHTML+RDFa document
(although future versions of this or related specifications may do
so).

Developers of tools that process fragments, or authors of fragments
for manual inclusion, should also bear in mind what will happen to
their fragment once it is included in an XHTML+RDFa document,
and are advised to carefully consider the amount of 'context'
information that will be needed in order to ensure a correct
interpretation of their fragment.

3.10. A description of RDFa in RDF terms

 The following is a brief description of RDFa in terms of the RDF
terminology introduced here. It may be useful to readers with an RDF
background:

The aim of RDFa is to allow a single [RDF graph] to be carried in
various types of document mark-up. However, this specification deals
only with RDFa in
XHTML. An [RDF graph] comprises [node]s linked by relationships. The
basic unit of an [RDF graph] is a [triple], in which a subject [node]
is linked to an object [node]
via a [predicate]. The [subject] [node] is always either a [URI
reference] or a [blank node (or bnode)], the [predicate] is always a
[URI reference], and the object of a statement can be a [URI
reference], a [literal], or a [bnode].

In RDFa, a subject [URI reference] is generally indicated using
@about, and predicates are represented using one of @property, @rel,
or @rev. Objects which are [URI reference]s are represented using
@href, @resource or @src, whilst objects that are [literal]s are
represented either
with @content or the content of the element in question (with an
optional datatype expressed using @datatype).


4. Conformance Requirements

This section is normative.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to
be interpreted as described in [RFC2119].

Note that all examples in this document are informative, and are not
meant to be interpreted as normative requirements.

4.1. Document Conformance

A strictly conforming XHTML+RDFa document is a document that requires
only the facilities described as mandatory in this specification. Such
a document satisfies the following criteria:



The document MUST conform to the constraints expressed in the schemas
in  Appendix A - XHTML+RDFa Document Type Definition.



The local part of the root element of the document MUST be html.



The start tag of the root element of the document MUST explicitly
contain a default namespace declaration for the XHTML namespace
[XMLNS].
The namespace URI for XHTML is defined to be
http://www.w3.org/1999/xhtml.


Sample root element


<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">




There SHOULD be a @version attribute on the html element with the
value "XHTML+RDFa 1.0"



Example of an XHTML+RDFa 1.0 document


<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml" 
    version="XHTML+RDFa 1.0"
    xml:lang="en">
  <head>
    <title>Virtual Library</title>
  </head>
  <body>
    <p>Moved to <a
href="http://example.org/">example.org</a>.</p>
  </body>
</html>



Note that in this example, the XML declaration is included. An XML
declaration like the one above is not required in all XML documents.
XHTML document authors SHOULD use XML
declarations in all their documents. XHTML document authors MUST use
an XML declaration when the character encoding of the document is
other than the default UTF-8 or UTF-16
and no encoding is specified by a higher-level protocol.

XHTML+RDFa documents SHOULD be labeled with the Internet Media Type
"application/xhtml+xml" as defined in [RFC3236]. For further
information on using media types with XHTML family markup languages,
see the informative note [XHTMLMIME].

4.2. User Agent Conformance

A conforming user agent MUST support all of the features required in
this specification. A conforming user agent must also support the User
Agent
conformance requirements as defined in XHTML Modularization [XHTMLMOD]
section on "XHTML Family User Agent Conformance".

4.3. RDFa Processor Conformance

A conforming RDFa Processor MUST make available to a consuming
application a single [RDF graph] containing all possible triples
generated
by using the rules in the Processing Model section. This specification
uses the term [default graph] to mean all of the
triples asserted by a document according to the Processing Model
section.

A conforming RDFa Processor MAY make available additional triples that
have been generated using rules not described here, but these triples
MUST NOT be made available in the
[default graph]. (Whether these additional triples are made available
in one or more additional [RDF graph]s
is implementation-specific, and therefore not defined here.)

Since XHTML+RDFa is based upon XHTML Modularization [XHTMLMOD], and
since XHTML Modularization requires that whitespace is preserved,
conforming processors must preserve whitespace in both [plain
literal]s and [XML literals]. However, it
may be the case that the architecture in which a processor operates
does not make all whitespace available. It is therefore advisable for
authors who would like to make their documents consumable
across different processors, to remove any unnecessary whitespace in
their mark-up.


5. Processing Model

This section is normative.

 This section looks at a generic set of processing rules for creating
a set of triples that represent the structured data present in an
XHTML+RDFa document. Processing need not follow the DOM
traversal technique outlined here, although the effect of following
some other manner of processing must be the same as if the processing
outlined here were followed. The processing model is
explained using the idea of DOM traversal which makes it easier to
describe (particularly in relation to the [evaluation context]).

Note that in this section, explanations about the processing model or
guidance to implementors are enclosed in sections like this.

5.1. Overview

 Parsing a document for RDFa triples is carried out by starting at the
document object, and then visiting each of its child elements in turn,
in document order, applying processing rules.
Processing is recursive in that for each child element the processor
also visits each of its child elements, and applies the same
processing rules.

 (Note that in some environments there will be little difference
between starting at the root element of the document, and starting at
the document object itself. However, we define it this way
since in some environments important information is present at the
document object level which is not present on the root element.)

 As processing continues, rules are applied which may generate
triples, and may also change the [evaluation context] information that
will then be
used when processing descendant elements.

 Note that we don't say anything about what should happen to the
triples generated, or whether more triples might be generated during
processing than are outlined here. However, to be conformant,
an RDFa processor needs to act as if at a minimum the rules in this
section are applied, and a single [RDF graph] produced. As described
in the RDFa Processor Conformance
section, any additional triples generated MUST NOT appear in the
[default graph].

5.2. Evaluation Context

 During processing, each rule is applied using information provided by
an [evaluation context]. An initial context is created when processing
begins, with the following set of values:


The [base]. This will usually be the URL of the document being
processed, but it could be some other URL, set by some other
mechanism, such as the XHTML
base element. The important thing is that it establishes a URL against
which relative paths can be resolved.

The [parent subject]. The initial value will be the same as the
initial value of [base], but it will usually
change during the course of processing.

The [parent object]. In some situations the object of a statement
becomes the subject of any nested statements, and this property is
used to convey
this value. Note that this value may be a bnode, since in some
situations a number of nested statements are grouped together on one
bnode. This means that the bnode must be set in the containing
statement and passed down, and this property is used to convey this
value.

A list of current, in-scope [URI mappings].

A list of [incomplete triple]s. A triple can be incomplete when no
object resource is provided alongside a predicate that requires a
resource
(i.e., @rel or @rev). The triples can be completed when a resource
becomes available, which will be when the next subject is specified
(part of the
process called [chaining]).

The [language]. Note that there is no default language.


During the course of processing new [evaluation context]s are created
which are passed to each child element. The rules described below will
determine the values of the items in the context. Additionally, some
rules will cause new triples to be created by combining information
provided by an element with information from the [evaluation context].

During the course of processing a number of locally scoped values are
needed, as follows:


An initially empty list of [URI mapping]s, called the [local list of
URI mappings].

An initially empty [list of incomplete triples], called the [local
list of
incomplete triples].

An initially empty [language] value.

A [recurse] flag. Processing generally continues recursively through
the entire tree of elements available. However, if an author indicates
that some
branch of the tree should be treated as an XML literal, no further
processing should take place on that branch, and setting this flag to
false would have that effect.

A [skip element] flag, which indicates whether the [current element]
can safely be ignored since it has
no relevant RDFa attributes. Note that descendant elements will still
be processed.

A [new subject] value, which once calculated will set the [parent
subject] property in an [evaluation context], as well as being used to
complete any [incomplete triple]s, as described in the next
section.

A value for the [current object literal], the literal to use when
creating triples that have a literal object.

A value for the [current object resource], the resource to use when
creating triples that have a resource object.


5.3. Chaining

RDFa has the notion of [chaining] which aims to combine statements
together in as intuitive a way as possible, so as avoid unnecessary
repetition of
mark-up. For example, if an author were to add statements as children
of an object that was a resource, these statements should be
interpreted as being about that resource:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany">
    <span property="dbp:conventionalLongName">Federal Republic
of Germany</span>
  </div>
</div>



 In this example we can see that an object resource ('Germany'), has
become the subject for nested statements. This mark-up also
illustrates the basic chaining pattern of 'A has a B has a C'
(i.e., Einstein has a birth place of Germany, which has a long name of
"Federal Republic of Germany").

It's also possible for the subject of nested statements to provide the
object for containing statements—essentially the reverse of the
example we have just seen. To illustrate,
we'll take an example of the type of chaining just described, and show
how it could be marked up more efficiently. To start, we mark up the
fact that Albert Einstein had both German and American
citizenship:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <div rel="dbp:citizenship"
resource="http://dbpedia.org/resource/Germany"></div>
  <div rel="dbp:citizenship"
resource="http://dbpedia.org/resource/United_States"></div>
</div>



Now, we show the same information, but this time we create an
[incomplete triple] from the citizenship part, and then use any number
of further
subjects to 'complete' that triple, as follows:



<div about="http://dbpedia.org/resource/Albert_Einstein"
rel="dbp:citizenship">
  <span
about="http://dbpedia.org/resource/Germany"></span>
  <span
about="http://dbpedia.org/resource/United_States"></span>
</div>



 In this example, the [incomplete triple] actually gets completed
twice, once for Germany and once for the USA, giving exactly the same
information
as we had in the earlier example:



<http://dbpedia.org/resource/Albert_Einstein>
  dbp:citizenship <http://dbpedia.org/resource/Germany> .
<http://dbpedia.org/resource/Albert_Einstein>
  dbp:citizenship <http://dbpedia.org/resource/United_States> .



 Chaining can sometimes involve elements containing relatively minimal
mark-up, for example showing only one resource, or only one predicate.
Here the img element is used to carry a
picture of Einstein:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <div rel="foaf:depiction">
    <img
src="http://en.wikipedia.org/wiki/Image:Albert_Einstein_Head.jpg"
/>
  </div>
</div>



 When such minimal mark-up is used, any of the resource-related
attributes could act as a subject or an object in the chaining:



    <div about="http://dbpedia.org/resource/Albert_Einstein">
      <div rel="dbp:citizenship">
        <span
about="http://dbpedia.org/resource/Germany"></span>
        <span
about="http://dbpedia.org/resource/United_States"></span>
      </div>
    </div>
  



5.4. CURIE and URI Processing

 Since RDFa is ultimately a means for transporting RDF, then a key
concept is the resource and its manifestation as a URI. Since RDF
deals with complete URIs (not relative paths), then
when converting RDFa to triples, any relative URIs will need to be
resolved relative to the base URI, using the algorithm defined in
section 5 of RFC 3986 [URI],
Reference Resolution.

 Many of the attributes that hold URIs are also able to carry 'compact
URIs' or CURIEs. A CURIE is a convenient way to represent a long URI,
by replacing a leading section of the URI with a
substitution token. It's possible for authors to define a number of
substitution tokens as they see fit; the full URI is obtained by
locating the mapping defined by a token from a list of in-scope
tokens, and then simply concatenating the second part of the CURIE
onto the mapped value.

For example, the full URI for Albert Einstein on DPPedia is:



http://dbpedia.org/resource/Albert_Einstein



This can be shortened by authors to make the information easier to
manage, using a CURIE. The first step is for the author to create a
prefix mapping that links a prefix to some leading segment of
the URI. In RDFa these mappings are expressed using the XML namespace
syntax:



<div xmlns:db="http://dbpedia.org/">
  ...
</div>



Once the prefix has been established, an author can then use it to
shorten a URI as follows:



<div xmlns:db="http://dbpedia.org/">
  <div about="[db:resource/Albert_Einstein]">
    ...
  </div>
</div>



 The author is free to break the URI at any point, as long as it
begins at the left end. However, since a common use of CURIEs is to
make available libraries of terms and values, the prefix will
usually be mapped to some common segment that provides the most
re-use, often provided by those who manage the library of terms. For
example, since DBPedia contains an enormous list of resources, it
is more efficient to create a prefix mapping that uses the base
location of the resources:



<div xmlns:dbr="http://dbpedia.org/resource/">
  <div about="[dbr:Albert_Einstein]">
    ...
  </div>
  <div about="[dbr:Baruch_Spinoza]">
    ...
  </div>
</div>



5.4.1. Scoping of Prefix Mappings

 Since CURIE mappings are created by authors via the XML namespace
syntax [XMLNS] an RDFa processor MUST take into account the
hierarchical nature of prefix
declarations. For example, the URIs expressed by the following two
CURIEs are different, despite the common prefix, because the prefix
mappings are locally scoped:



<div xmlns:dbr="http://dbpedia.org/resource/">
  <div about="[dbr:Albert_Einstein]">
    ...
  </div>
</div>
<div xmlns:dbr="http://someotherdb.org/resource/">
  <div about="[dbr:Albert_Einstein]">
    ...
  </div>
</div>



5.4.2. Converting a CURIE to a URI

 Since a CURIE is merely a means for abbreviating a URI, its value is
a URI, rather than the abbreviated form. Obtaining a URI from a CURIE
involves the following steps:


Split the CURIE at the colon to obtain the prefix and the resource.

Using the prefix and the current in-scope mappings, obtain the URI
that the prefix maps to.

Concatenate the mapped URI with the resource value, to obtain an
absolute URI.


Note that it is generally considered a good idea not to use relative
paths in namespace declarations, but since it is possible that an
author may ignore this guidance, it is
further possible that the URI obtained from a CURIE is relative.
However, since all URIs must be resolved relative to [base] before
being used to create triples,
the use of relative paths should not have any effect on processing.

5.4.3. General Use of CURIEs in Attributes

 There are a number of ways that attributes will make use of CURIEs,
and they need to be dealt with differently. These are:


An attribute may allow one or more CURIE-only values, disallowing
other types of value. In this case any value that is not a 'curie'
according to the definition in the section CURIE Syntax Definition
MUST be ignored; this means that not only will there be no error
reporting, but also the RDFa processor should act as if the value
simply did not exist.

An attribute may allow one or more values that are a mixture of CURIEs
and full URIs. In this case any value that is not surrounded by square
brackets, as defined by 'safe_curie' in the section
CURIE Syntax Definition, will be processed as if it was a URI. If the
value is surrounded by square brackets, then the inner content must
conform to the 'curie'
definiton, and as before, if it does not then the value MUST be
ignored.


An example of an attribute that can contain CURIE and non-CURIE values
is @about. As described, any CURIEs expressed in the attribute must
follow the format of a [safe CURIE]. So to express a URI directly, an
author might do this:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  ...
</div>



whilst to express a CURIE they would do this:



<div about="[dbr:Albert_Einstein]">
  ...
</div>



 Since non-CURIE values MUST be ignored, the following value in @about
would not set a new subject, since the CURIE has no prefix separator.



<div about="[Albert_Einstein]">
  ...
</div>



However, this mark-up would set a subject, since it is not a CURIE,
but a valid relative URI:



<div about="Albert_Einstein">
  ...
</div>



 There is one exception to this; @rel and @rev can also take any value
from the list in the section on The rel attribute,
and any matching value MUST be treated as if it was a full URI with
the XHTML vocabulary as its prefix mapping. This is discussed further
in the next section.

5.4.4. Use of CURIEs in Specific Attributes

 The general rules discussed in the previous section apply to the RDFa
attributes in the following ways:


@about and @resource support either a URI or a CURIE (expressed as a
[safe CURIE] ).

@href and @src support only a URI.

@property, @datatype and @typeof support only CURIE values.

@rel and @rev support both XHTML link types and CURIEs.


 Note that unlike @about and @resource, @rel and @rev do not
differentiate their two types
of data by using [safe CURIE]s. Instead, any value that matches an
entry in the list of link types in the section The rel attribute, MUST
be treated as if it was a URI within the XHTML vocabulary, and all
other values must be CURIEs. This means that either of the following
examples:



<link rel="next" href="http://example.org/page2.html" />
<link rel="xhv:next" href="http://example.org/page2.html" />



would generate this triple:



<> <http://www.w3.org/1999/xhtml/vocab#next>
<http://example.org/page2.html> .



 Note that only values in the link type list have this special
behaviour, which means that any value that is not in the list and is
not a valid CURIE MUST not
generate triples in the [default graph] . For example, no triples
would be generated in the [default
graph] by the following mark-up:



<link rel="foobar" href="http://example.org/page7.html" />



5.4.5. Referencing Blank Nodes

In RDFa, it is possible to establish relationships using various types
of resource references, including [bnode]s. If a subject or object is
defined using a
CURIE, and that CURIE explicitly names a [bnode], then a conforming
parser MUST create the bnode when it is encountered during parsing.
The parser MUST also ensure that no bnodes created automatically (as a
result of [chaining]) have names that collide with bnodes that
are defined by explicit reference in a CURIE.

Consider the following example:



<link about="[_:john]" rel="foaf:mbox"
  href="mailto:john@example.org" />
<link about="[_:sue]" rel="foaf:mbox"
  href="mailto:sue@example.org" />
<link about="[_:john]" rel="foaf:knows"
  resource="[_:sue]" />



In the above fragment, two bnodes are explicitly created as the
subject of triples. Those bnodes are then referenced to demonstrate
the relationship between the parties. After processing, the
following triples will be generated:



_:john foaf:mbox <mailto:john@example.org> .
_:sue foaf:mbox <mailto:sue@example.org> .
_:john foaf:knows _:sue .



5.5. Sequence

 Processing would normally begin after the document to be parsed has
been completely loaded. However, there is no requirement for this to
be the case, and it is certainly possible to use a
stream-based approach, such as SAX [http://en.wikipedia.org/wiki/SAX]
to extract the RDFa information. However, if some approach other than
the DOM traversal technique defined here is used, it is
important to ensure that any meta or link elements processed in the
head of the document honor any occurrences of base which may appear 
after those elements. (In other words, XHTML processing rules must
still be applied, even if document processing takes place in a
non-HTML environment such as a search indexer.)

 At the beginning of processing, an initial [evaluation context] is
created, as follows:


the [base] is set to either the URL of the document or the value
specified in the base element, if present; 

Note that XHTML 1.1, and therefore XHTML+RDFa, does NOT permit the use
of @xml:base, so the only way to change the [base] is via the base
element. If some other XML dialect that supports @xml:base eventually
implements RDFa, a conforming RDFa parser for that host
language will likely process @xml:base and use its value to set
[base].


the [parent subject] is set to the [base] value;

the [parent object] is set to null;

the [list of URI mappings] is empty;

the [list of incomplete triples] is empty;

the [language] is set to null.


 Processing begins by applying the processing rules below to the
document object, in the context of this initial [evaluation context].
All elements
in the tree are also processed according to the rules described below,
depth-first, although the [evaluation context] used for each set of
rules will
be based on previous rules that may have been applied.

 The processing rules are:


First, the local values are initialized, as follows: 


the [recurse] flag is set to 'true';

the [skip element] flag is set to 'false';

[new subject] is set to null;

[current object resource] is set to null;

the [local list of URI mappings] is set to the list of URI mappings
from the [evaluation
context];

the [local list of incomplete triples] is set to null;

the [current language] value is set to the [language] value from the
[evaluation context].


Note that some of the local variables are temporary containers for
values that will be passed to descendant elements via an [evaluation
context]. In some cases the containers will have the same name, so to
make it clear which is being acted upon in the following steps, the
local version of an item will generally
be referred to as such.


Next the [current element] is parsed for [URI mapping]s and these are
added to the [local list of URI mappings]. Note that a [URI mapping]
will simply overwrite any current mapping in the list
that has the same name; 

Mappings are provided by @xmlns. The value to be mapped is set by the
XML namespace prefix, and the value to map is the value of the
attribute—a URI. Note that the URI is not processed in any way;
in particular if it is a relative path it is not resolved against the
current [base]. Authors
are advised to follow best practice for using namespaces, which
includes not using relative paths.


The [current element] is also parsed for any language information, and
if present, [current language]
is set accordingly; 

Language information can be provided using the general-purpose XML
attribute @xml:lang.


If the [current element] contains no @rel or @rev attribute, then the
next step is to establish a
value for [new subject]. Any of the attributes that can carry a
resource can set [new subject]; 

[new subject] is set to the URI obtained from the first match from the
following rules: 


by using the URI from @about, if present, obtained according to the
section on CURIE and URI Processing;

otherwise, by using the URI from @src, if present, obtained according
to the section on CURIE and URI Processing.

otherwise, by using the URI from @resource, if present, obtained
according to the section on CURIE and URI Processing;

otherwise, by using the URI from @href, if present, obtained according
to the section on CURIE and URI Processing.


If no URI is provided by a resource attribute, then the first match
from the following rules will apply:


if the element is the head or body element then act as if there is an
empty @about present, and process it according to the rule for @about,
above;

if @typeof is present, obtained according to the section on CURIE and
URI Processing, then [new
subject] is set to be a newly created [bnode].

otherwise, if [parent object] is present, [new subject] is set to the
value of [parent object]. Additionally, if @property is not present
then the [skip element]
flag is set to 'true';




If the [current element] does contain a @rel or @rev attribute, then
the next step is to
establish both a value for [new subject] and a value for [current
object resource]: 

[new subject] is set to the URI obtained from the first match from the
following rules: 


by using the URI from @about, if present, obtained according to the
section on CURIE and URI Processing;

otherwise, by using the URI from @src, if present, obtained according
to the section on CURIE and URI Processing.


If no URI is provided then the first match from the following rules
will apply:


if the element is the head or body element then act as if there is an
empty @about present, and process it according to the rule for @about,
above;

if @typeof is present, obtained according to the section on CURIE and
URI Processing, then [new
subject] is set to be a newly created [bnode];

otherwise, if [parent object] is present, [new subject] is set to
that.


Then the [current object resource] is set to the URI obtained from the
first match from the following rules:


by using the URI from @resource, if present, obtained according to the
section on CURIE and URI Processing;

otherwise, by using the URI from @href, if present, obtained according
to the section on CURIE and URI Processing.


Note that final value of the [current object resource] will either be
null (from initialization) or a full URI.



If in any of the previous steps a [new subject] was set to a non-null
value, it is now used to provide a subject for type values; 

One or more 'types' for the [new subject] can be set by using @typeof.
If present, the attribute must
contain one or more URIs, obtained according to the section on URI and
CURIE Processing, each of which is used to generate a triple as
follows: 


subject

[new subject]

predicate

http://www.w3.org/1999/02/22-rdf-syntax-ns#type

object

full URI of 'type'



Note that none of this block is executed if there is no [new subject]
value, i.e., [new
subject] remains null.


If in any of the previous steps a [current object resource] was set to
a non-null value, it is now used to generate triples: 

Predicates for the [current object resource] can be set by using one
or both of the @rel and
@rev attributes: 


If present, @rel may contain one or more URIs, obtained according to
the section on CURIE and URI Processing each of which is used to
generate a triple as follows: 


subject

[new subject]

predicate

full URI

object

[current object resource]



If present, @rev may contain one or more URIs, obtained according to
the section on CURIE and URI Processing each of which is used to
generate a triple as follows: 


subject

[current object resource]

predicate

full URI

object

[new subject]






If however [current object resource] was set to null, but there are
predicates present, then they must be stored as [incomplete triple]s,
pending the discovery of a subject that can be used as the object.
Also, [current object
resource] should be set to a newly created [bnode]; 

Predicates for [incomplete triple]s can be set by using one or both of
the @rel and @rev attributes: 


If present, @rel must contain one or more URIs, obtained according to
the section on CURIE and URI Processing each of which is added to
the [local list of incomplete triples] as follows: 


predicate

full URI

direction

forward



If present, @rev must contain one or more URIs, obtained according to
the section on CURIE and URI Processing, each of which is added to
the [local list of incomplete triples] as follows: 


predicate

full URI

direction

reverse






The next step of the iteration is to establish any [current object
literal]; 

Predicates for the [current object literal] can be set by using
@property. If present, one or
more URIs are obtained according to the section on CURIE and URI
Processing, and then the actual literal value is obtained as follows: 


as a [typed literal] if: 


@datatype is present, and does not have an empty value, and is not set
to rdf:XMLLiteral.


The actual literal is either the value of @content (if present) or a
string created by concatenating the value of all descendant text
nodes, of the [current element] in turn. The final string includes the
datatype URI, as described in [RDF-CONCEPTS], which will
have been obtained according to the section on CURIE and URI
Processing.


as a [plain literal] if: 


@content is present;

or all children of the [current element] are text nodes;

or there are no child nodes (in which case the literal value is the
empty string);

or the body of the [current element] does have non-text child nodes
but @datatype is present, with an
empty value.


Additionally, if there is a value for [current language] then the
value of the [plain literal] should
include this language information, as described in [RDF-CONCEPTS]. The
actual literal is either the value of @content (if
present) or a string created by concatenating the text content of each
of the descendant elements of the [current element] in document
order.


as an [XML literal] if: 


the [current element] has any child nodes that are not simply text
nodes, and @datatype is not present, or is present, but
is set to rdf:XMLLiteral.


The value of the [XML literal] is a string created by serializing to
text, all nodes that are descendants of the [current element], i.e.,
not including the element itself, and giving it a datatype of
rdf:XMLLiteral.



The [current object literal] is then used with each predicate to
generate a triple as follows:


subject

[new subject]

predicate

full URI

object

[current object literal]



Once the triple has been created, if the [datatype] of the [current
object literal] is 
rdf:XMLLiteral, then the [recurse] flag is set to false.


If the [skip element] flag is 'false', and [new subject] was set to a
non-null value, then any [incomplete triple]s within the current
context should be completed: 

The [list of incomplete triples] from the current [evaluation
context] (not the [local list of incomplete triples]) will contain
zero or more predicate URIs. This list is iterated, and
each of the predicates is used with [parent subject] and [new subject]
to generate a triple. Note that at each
level there are two, lists of [incomplete triple]s; one for the
current processing level (which is passed to each child element in the
previous step), and one that was received as part of the [evaluation
context]. It is the latter that is used in processing during this
step.

Note that each [incomplete triple] has a [direction] value that it
used to
determine what will become the subject, and what will become the
object, of each generated triple: 


If [direction] is 'forward' then the following triple is generated: 


subject

[parent subject]

predicate

the predicate from the iterated [incomplete triple]

object

[new subject]



If [direction] is not 'forward' then this is the triple generated: 


subject

[new subject]

predicate

the predicate from the iterated [incomplete triple]

object

[parent subject]






If the [recurse] flag is 'true', all elements that are children of the
[current element] are processed using
the rules described here, using a new [evaluation context],
initialized as follows: 


If the [skip element] flag is 'true' then the new [evaluation context]
is a copy of the current context
that was passed in to this level of processing, with the [language]
and [list of URI mappings] values
replaced with the local values;

Otherwise, the values are: 


the [base] is set to the [base] value of the current [evaluation
context];

the [parent subject] is set to the value of [new subject], if
non-null, or the value of the [parent subject] of the current
[evaluation context];

the [parent object] is set to value of [current object resource], if
non-null, or the
value of [new subject], if non-null, or the value of the [parent
subject] of the current [evaluation context];

the [list of URI mappings] is set to the [local list of URI mappings];

the [list of incomplete triples] is set to the [local list of
incomplete
triples];

[language] is set to the value of [current language].







6. RDFa Processing in detail

This section is normative.

 This section provides an in-depth examination of the processing steps
described in the previous section. It also includes examples which may
help clarify some of the steps involved.

 The key to processing is that a triple is generated whenever a
predicate/object combination is detected. The actual triple generated
will include a subject that may have been set previously, so
this is tracked in the current [evaluation context] and is called the
[parent subject]. Since the subject
will default to the current document if it hasn't been set explicitly,
then a predicate/object combination is always enough to generate one
or more triples.

 The attributes for setting a predicate are @rel, @rev and @property,
whilst the attributes for setting an object are
@resource, @href, @content, and @src. @typeof is unique in that it
sets both a predicate and an object at the same time (and also a
subject when it appears in the absence of other attributes that would
set a subject). Inline content might also set an
object, if @content is not present, but @property is.

6.1. Changing the evaluation context

6.1.1. Setting the current subject

When triples are created they will always be in relation to a subject
resource which is provided either by [new subject] (if there are rules
on the
current element that have set a subject) or [parent subject], as
passed in via the [evaluation context].
This section looks at the specific ways in which these values are set.
Note that it doesn't matter how the subject is arrived at, so in this
section we use the idea of the [current subject] which may be either
[new subject] or [parent subject].

6.1.1.1. The current document

When parsing begins, the [current subject] will be the URI of the
document being parsed, or a value as set by base according to normal
XHTML processing rules. This means that any metadata found in the head
of the document will concern the document itself:



<html>
  <head>
    <title>Jo's Friends and Family Blog</title>
    <link rel="foaf:primaryTopic" href="#bbq" />
    <meta property="dc:creator" content="Jo" />
  </head>
  <body>
    ...
  </body>
</html>



This would generate the following triples:



<> foaf:primaryTopic <#bbq> .
<> dc:creator "Jo" .



It is possible for the data to appear elsewhere in the document:



<html>
  <head>
    <title>Jo's Blog</title>
  </head>
  <body>
    <h1><span property="dc:creator">Jo</span>'s
blog</h1>
    <p>
      Welcome to my blog.
    </p>
  </body>
</html>



which would still generate the triple:



<> dc:creator "Jo" .



The value of base may change the initial value of [current subject]:



<html>
  <head>
    <base href="http://www.example.org/jo/blog" />
    <title>Jo's Friends and Family Blog</title>
    <link rel="foaf:primaryTopic" href="#bbq" />
    <meta property="dc:creator" content="Jo" />
  </head>
  <body>
    ...
  </body>
</html>



A parser should now generate the following triples, regardless of the
URL from which the XHTML document is served:



<http://www.example.org/jo/blog> foaf:primaryTopic <#bbq>
.
<http://www.example.org/jo/blog> dc:creator "Jo" .



6.1.1.2. Using @about

As processing progresses, any @about attributes will change the
[current subject]. The value of 
@about is a URI or a CURIE. If it is a relative URI then it needs to
be resolved against the current [base] value. To illustrate how this
affects the
statements, note in this mark-up how the properties inside the body
element become part of a new calendar event object, rather than
referring to the document as they do in the head of
the document:



<html>
  <head>
    <title>Jo's Friends and Family Blog</title>
    <link rel="foaf:primaryTopic" href="#bbq" />
    <meta property="dc:creator" content="Jo" />
  </head>
  <body>
    <p about="#bbq" typeof="cal:Vevent">
      I'm holding
      <span property="cal:summary">
        one last summer barbecue
      </span>,
      on
      <span property="cal:dtstart"
content="2007-09-16T16:00:00-05:00" 
            datatype="xsd:dateTime">
        September 16th at 4pm
      </span>.
    </p>
  </body>
</html>



With this mark-up a parser should generate the following triples:



<> foaf:primaryTopic <#bbq> .
<> dc:creator "Jo" .
<#bbq> rdf:type cal:Vevent .
<#bbq> cal:summary "one last summer barbecue" .
<#bbq> cal:dtastart "2007-09-16T16:00:00-05:00"^^xsd:dateTime .



Other kinds of resources can be used to set the [current subject], not
just references to web-pages. Although not advised, email addresses
might be
used to represent a person:



John knows
<a about="mailto:john@example.org"
  rel="foaf:knows" href="mailto:sue@example.org">Sue</a>.

Sue knows
<a about="mailto:sue@example.org"
  rel="foaf:knows" href="mailto:jim@example.org">Jim</a>.



This should generate the following triples:



<mailto:john@example.org> foaf:knows
<mailto:sue@example.org> .
<mailto:sue@example.org> foaf:knows
<mailto:jim@example.org> .



Similarly, authors may make statements about images:



<div about="photo1.jpg">
  this photo was taken by
  <span property="dc:creator">Mark Birbeck</span>
</div>



which should generate the following triples:



<photo1.jpg> dc:creator "Mark Birbeck" .



6.1.1.3. Using @src

 If @about is not present, then @src is next in priority order, for
setting the subject of a statement. A typical use would be to indicate
the
licensing type of an image:



<img src="photo1.jpg" rel="license"
resource="http://creativecommons.org/licenses/by/2.0/" />



 Since there is no difference between @src and @about, then the
information expressed in the last example in the section on 
@about (the creator of an image), could be expressed as follows:



<img src="photo1.jpg"
  rel="license" resource="http://creativecommons.org/licenses/by/2.0/"
  property="dc:creator" content="Mark Birbeck"
/>



 Since normal chaining rules will apply, the image URL can also be
used to complete hanging triples:



<div about="http://www.blogger.com/profile/1109404"
rel="foaf:img">
  <img src="photo1.jpg"
    rel="license"
resource="http://creativecommons.org/licenses/by/2.0/"
    property="dc:creator" content="Mark Birbeck"
  />
</div>



The complete mark-up yields three triples:



<http://www.blogger.com/profile/1109404> foaf:img
<photo1.jpg> .
<photo1.jpg> xhv:license
<http://creativecommons.org/licenses/by/2.0/> .
<photo1.jpg> dc:creator "Mark Birbeck" .



6.1.1.4. Creating a new item with @typeof

 Whilst @about explicitly creates a new context for statements,
@typeof does so implicitly. @typeof works differently
to other ways of setting a predicate since the predicate is always
rdf:type, which means that the processor only requires one attribute,
the value of the type.

Since @typeof is setting the type of an item, this means that if no
item exists one should automatically be created. This involves
generating a new bnode, and is examined
in more detail below; it is mentioned here because the bnode used by
the new item will become the subject for further statements.

 For example, an author may wish to create mark-up for a person using
the FOAF vocabulary, but without having a clear identifier for the
item:



<div typeof="foaf:Person">
  <span property="foaf:name">Albert Einstein</span>
  <span property="foaf:givenname">Albert</span>
</div>



 This mark-up would cause a bnode to be created which has a 'type' of
foaf:Person, as well as name and given name properties:



_:a rdf:type foaf:Person .
_:a foaf:name "Albert Einstein" .
_:a foaf:givenname "Albert" .



A bnode is simply a unique identifier that is only available to the
processor, not to any external software. By generating values
internally, the processor is able to keep
track of properties for _:a as being distinct from _:b. But by not
exposing these values to any external software, it is possible to have
complete control over the
identifier, as well as preventing further statements being made about
the item.

6.1.1.5. Determining the subject with neither @about nor @typeof

 As described in the previous two sections, @about will always take
precedence and mark a new subject, but if no @about value is available
then
@typeof will do the same job, although using an implied identifier,
i.e., a bnode.

 But if neither @about or @typeof are present, there are a number of
ways that the subject could be arrived at. One of these is to
'inherit' the
subject from the containing statement, with the value to be inherited
set either explicitly, or implicitly.

6.1.1.5.1. Inheriting subject from @resource

 The most usual way that an inherited subject might get set would be
when the parent statement has an object that is a resource. Returning
to the earlier example, in which the long name for
Germany was added, the following mark-up was used:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany" />
  <span about="http://dbpedia.org/resource/Germany"
    property="dbp:conventionalLongName">Federal Republic of
Germany</span>
</div>



 In an earlier illustration the subject and object for Germany were
elided by removing the @resource, relying on the @about to set the
object:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace">
    <span about="http://dbpedia.org/resource/Germany"
      property="dbp:conventionalLongName">Federal Republic of
Germany</span>
  </div>
</div>



 but it is also possible for authors to achieve the same effect by
removing the @about and leaving the @resource:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany">
    <span property="dbp:conventionalLongName">Federal Republic
of Germany</span>
  </div>
</div>



 In this situation, all statements that are 'contained' by the object
resource representing Germany (the value in @resource) will have the
same subject, making it easy
for authors to add additional statements:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany">
    <span property="dbp:conventionalLongName">Federal Republic
of Germany</span>
    <span rel="dbp:capital"
resource="http://dbpedia.org/resource/Berlin" />
  </div>
</div>



Looking at the triples that a parser would generate, we can see that
we actually have two groups of statements; the first group are set to
refer to the @about that
contains them:



<http://dbpedia.org/resource/Albert_Einstein> foaf:name "Albert
Einstein" .
<http://dbpedia.org/resource/Albert_Einstein> dbp:dateOfBirth
"1879-03-14"^^xsd:date .
<http://dbpedia.org/resource/Albert_Einstein> dbp:birthPlace
<http://dbpedia.org/resource/Germany> .



whilst the second group refer to the @resource that contains them:



<http://dbpedia.org/resource/Germany>
  dbp:conventionalLongName "Federal Republic of Germany" .
<http://dbpedia.org/resource/Germany>
  dbp:capital <http://dbpedia.org/resource/Berlin> .



 Note also that the same principle described here applies to @src and
@href.

6.1.1.5.2. Inheriting an anonymous subject

 There will be occasions when the the author wants to elide the
subject and object as shown above, but is not concerned to name the
resource that is common to the two statements (i.e., the object
of the first statement, which is the subject of the second). For
example, to indicate that Einstein was influenced by Spinoza the
following mark-up could well be used:



<div about="http://dbpedia.org/resource/Baruch_Spinoza"
rel="dbp:influenced">
  <div about="http://dbpedia.org/resource/Albert_Einstein">
    <span property="foaf:name">Albert Einstein</span>
    <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  </div>
</div>



 A parser should generate the following triples:



<http://dbpedia.org/resource/Baruch_Spinoza>
  dbp:influenced <http://dbpedia.org/resource/Albert_Einstein> .
<http://dbpedia.org/resource/Albert_Einstein> foaf:name "Albert
Einstein" .
<http://dbpedia.org/resource/Albert_Einstein> dbp:dateOfBirth
"1879-03-14"^^xsd:date .



 However, an author could just as easily say that Spinoza influenced
something by the name of Albert Einstein, that was born on March 14th,
1879:



<div about="http://dbpedia.org/resource/Baruch_Spinoza"
rel="dbp:influenced">
  <div>
    <span property="foaf:name">Albert Einstein</span>
    <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  </div>
</div>



 In RDF terms, the item that 'represents' Einstein is anonymous, since
it has no URI to identify it. However, the item is given an
automatically generated bnode, and it is onto this
idenfifier that all child statements are attached:

 A parser should generate the following triples:



<http://dbpedia.org/resource/Baruch_Spinoza> dbp:influenced _:a
.
_:a foaf:name "Albert Einstein" .
_:a dbp:dateOfBirth "1879-03-14"^^xsd:date .



 Note that the div is superfluous, and a parser should create the
intermediate object even if the element is removed:



<div about="http://dbpedia.org/resource/Baruch_Spinoza"
rel="dbp:influenced">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
</div>



 An alternative pattern is to keep the div and move the @rel onto it:



<div about="http://dbpedia.org/resource/Baruch_Spinoza">
  <div rel="dbp:influenced">
    <span property="foaf:name">Albert Einstein</span>
    <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  </div>
</div>



 From the point of view of the mark-up, this latter layout is to be
preferred, since it draws attention to the 'hanging rel'. But from the
point of view of a parser, all of these permutations need
to be supported.

6.2. Completing 'incomplete triples'

 When a new subject is calculated, it is also used to complete any
incomplete triples that are pending. This situation arises when the
author wants to 'chain' a number of statements together. For
example, an author could have a statement that Albert Einstein was
born in Germany:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany" />
</div>



 and then a further statement that the 'long name' for Germany is the
Federal Republic of Germany:



<span about="http://dbpedia.org/resource/Germany"
  property="dbp:conventionalLongName">Federal Republic of
Germany</span>



 RDFa allows authors to insert this statement as a self-contained unit
into other contexts:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/Germany" />
  <span about="http://dbpedia.org/resource/Germany"
    property="dbp:conventionalLongName">Federal Republic of
Germany</span>
</div>



 But it also allows authors to avoid unnecessary repetition and to
'normalize' out duplicate identifiers, in this case the one for
Germany:



<div about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:birthPlace">
    <span about="http://dbpedia.org/resource/Germany"
      property="dbp:conventionalLongName">Federal Republic of
Germany</span>
  </div>
</div>



 When this happens the @rel for 'birth place' is regarded as a
'hanging rel' because it has not yet generated any triples, but these
'incomplete triples' are completed by
the @about that appears on the next line. The first step is therefore
to store the two parts of the triple that the parser does have, but
without an object:



<http://dbpedia.org/resource/Albert_Einstein> dbp:birthPlace ? .



 Then as processing continues, the parser encounters the subject of
the statement about the long name for Germany, and this is used in two
ways. First it is used to complete the 'incomplete
triple':



<http://dbpedia.org/resource/Albert_Einstein> dbp:birthPlace
<http://dbpedia.org/resource/Germany> .



and second it is used to generate its own triple:



<http://dbpedia.org/resource/Germany> dbp:conventionalLongName
"Federal Republic of Germany" .



 Note that each occurrence of @about will complete any incomplete
triples. For example, to mark up the fact that Albert Einstein had
both German and American citizenship,
an author need only specify one @rel value that is then used with
multiple @about values:



<div about="http://dbpedia.org/resource/Albert_Einstein"
rel="dbp:citizenship">
  <span about="http://dbpedia.org/resource/Germany" />
  <span about="http://dbpedia.org/resource/United_States" />
</div>



 In this example there is one incomplete triple:



<http://dbpedia.org/resource/Albert_Einstein> dbp:citizenship ?
.



 When the processor meets each of the @about values, this triple is
completed, giving:



<http://dbpedia.org/resource/Albert_Einstein>
  dbp:citizenship <http://dbpedia.org/resource/Germany> .
<http://dbpedia.org/resource/Albert_Einstein>
  dbp:citizenship <http://dbpedia.org/resource/United_States> .



 These examples show how @about completes triples, but there are other
situations that can have the same effect. For example, when @typeof
creates a new bnode (as described above), that will be used to
complete any 'incomplete triples'. To illustrate, to indicate that
Spinoza influenced both Einstein and Schopenhauer, the following
mark-up could be used:



<div about="http://dbpedia.org/resource/Baruch_Spinoza">
  <div rel="dbp:influenced">
    <div typeof="foaf:Person">
      <span property="foaf:name">Albert Einstein</span>
      <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
    </div>
    <div typeof="foaf:Person">
      <span property="foaf:name">Arthur
Schopenhauer</span>
      <span property="dbp:dateOfBirth"
datatype="xsd:date">1788-02-22</span>
    </div>          
  </div>
</div>



First the following incomplete triple is stored:



<http://dbpedia.org/resource/Baruch_Spinoza> dbp:influenced ? .



 Then when the parser processes the two occurences of @typeof, each
generates a bnode, which is used to both complete the 'incomplete
triple', and to set the subject for
further statements:



<http://dbpedia.org/resource/Baruch_Spinoza"> dbp:influenced _:a
.
_:a rdf:type foaf:Person .
_:a foaf:name "Albert Einstein" .
_:a dbp:dateOfBirth "1879-03-14"^^xsd:date .
<http://dbpedia.org/resource/Baruch_Spinoza"> dbp:influenced _:b
.
_:b rdf:type foaf:Person .
_:b foaf:name "Arthur Schopenhauer" .
_:b dbp:dateOfBirth "1788-02-22"^^xsd:date .



 Triples are also 'completed' if any one of @property, @rel or @rev
are present. However, unlike the situation when
@about or @typeof are present, all predicates are attached to one
bnode:



<div about="http://dbpedia.org/resource/Baruch_Spinoza"
rel="dbp:influenced">
  <span property="foaf:name">Albert Einstein</span>
  <span property="dbp:dateOfBirth"
datatype="xsd:date">1879-03-14</span>
  <div rel="dbp:citizenship">
    <span about="http://dbpedia.org/resource/Germany" />
    <span about="http://dbpedia.org/resource/United_States" />
  </div>
</div>



 This example has two 'hanging rels', and so two situations when
'incomplete triples' will be created. Processing would proceed as
follows; first an incomplete triple is stored:



<http://dbpedia.org/resource/Baruch_Spinoza> dbp:influenced ? .



 Next, the parser processes the predicate values for foaf:name,
dbp:dateOfBirth and dbp:citizenship, but note that only the first
needs to 'complete' the
'hanging rel'. So processing foaf:name generates two triples:



<http://dbpedia.org/resource/Baruch_Spinoza> dbp:influenced _:a
.
_:a foaf:name "Alber Einstein" .



 but processing dbp:dateOfBirth generates only one:



_:a dbp:dateOfBirth "1879-03-14"^^xsd:date .



Processing dbp:citizenship also uses the same bnode, but note that it
also generates its own 'incomplete triple':



  _:a dbp:citizenship ? .



As before, the two occurrences of @about complete the 'incomplete
triple', once each:



_:a dbp:citizenship <http://dbpedia.org/resource/Germany> .
_:a dbp:citizenship <http://dbpedia.org/resource/United_States>
.



 The entire set of triples that a parser should generate are as
follows:



<http://dbpedia.org/resource/Baruch_Spinoza> dbp:influenced _:a
.
_:a foaf:name "Alber Einstein" .
_:a dbp:dateOfBirth "1879-03-14"^^xsd:date .
_:a dbp:citizenship <http://dbpedia.org/resource/Germany> .
_:a dbp:citizenship <http://dbpedia.org/resource/United_States>
.



6.3. Object resolution

 Although objects have been discussed in the previous sections, as
part of the explanation of subject resolution, chaining, evaluation
contexts, and so on, this section will look at objects in
more detail.

There are two types of object, [URI resource]s and [literal]s.

A [literal] object can be set by using @property to express a
[predicate], and then using
either @content, or the inline text of the element that @property is
on. Note that the use of @content prohibits the
inclusion of rich markup in your literal. If the inline content of an
element accurately represents the object, then documents should rely
upon that rather than duplicating that data using the @content.

A [URI resource] object can be set using one of @rel or @rev to
express a [predicate], and then either using one of @href, @resource
or @src to provide an object resource
explicitly, or using the chaining techniques described above to obtain
an object from a nested subject, or from a bnode.

6.3.1. Literal object resolution

 An [object literal] will be generated when @property is present.
@property provides the
predicate, and the following sections describe how the actual literal
to be generated is determined.

6.3.1.1. Plain Literals

@content can be used to indicate a [plain literal], as follows:



<meta about="http://internet-apps.blogspot.com/"
      property="dc:creator" content="Mark Birbeck" />



The [plain literal] can also be specified by using the content of the
element:



<span about="http://internet-apps.blogspot.com/"
      property="dc:creator">Mark Birbeck</span>



 Both of these examples give the following triple:



<http://internet-apps.blogspot.com/> dc:creator "Mark Birbeck" .



The value of @content is given precedence over any element content, so
the following would give exactly the same triple:



<span about="http://internet-apps.blogspot.com/"
      property="dc:creator" content="Mark Birbeck">John
Doe</span>



6.3.1.1.1. Language Tags

RDF allows [plain literal]s to have a language tag, as illustrated by
the following example from 
[RDFTESTS-RDFMS-XMLLANG-TEST006]:



<http://example.org/node> 
  <http://example.org/property> "chat"@fr .



In RDFa the XML language attribute @xml:lang is used to add this
information, whether the plain literal is designated by @content, or
by the
inline text of the element:



<meta about="http://example.org/node"
  property="ex:property" xml:lang="fr" content="chat" />



Note that the language value can be inherited as defined in
[XML-LANG], so the following syntax will give the same triple as
above:



<html xmlns="http://www.w3.org/1999/xhtml" 
      xmlns:ex="http://www.example.com/ns/" xml:lang="fr">
  <head>
    <title xml:lang="en">Example</title>
    <meta about="http://example.org/node"
      property="ex:property" content="chat" />
  </head>
  ...
</html>



6.3.1.2. Typed literals

Literals can be given a data type using @datatype.

This can be represented in RDFa as follows:



<span property="cal:dtstart" content="2007-09-16T16:00:00-05:00" 
      datatype="xsd:dateTime">
  September 16th at 4pm
</span>.



The triples that this mark-up generates include the datatype after the
literal:



<> cal:dtstart "2007-09-16T16:00:00-05:00"^^xsd:dateTime .



6.3.1.3. XML Literals

XML documents cannot contain XML mark-up in their attributes, which
means it is not possible to represent XML within @content (the
following would cause an XML parser to
generate an error):



<head>
  <meta property="dc:title"
    content="E = mc<sup>2</sup>: The Most Urgent Problem
of Our Time" />
</head>



It does not help to escape the content, since the output would simply
be a string of text containing numerous ampersands:



<> dc:title "E = mc&lt;sup&gt;2&amp;lt;/sup&gt;:
The Most Urgent Problem of Our Time" .



RDFa therefore supports the use of normal mark-up to express XML
literals, by using @datatype:



<h2 property="dc:title" datatype="rdf:XMLLiteral">
  E = mc<sup>2</sup>: The Most Urgent Problem of Our Time
</h2>



This would generate the following triple, with the XML preserved in
the literal:



<> dc:title "E = mc<sup>2</sup>: The Most Urgent
Problem of Our Time"^^rdf:XMLLiteral .



 Note that this requires that a URI mapping for the prefix rdf has
been defined. To make authoring easier, if there are child elements
and no @datatype
attribute, then the effect is the same as if @datatype have been
explicitly set to rdf:XMLLiteral:



<h2 property="dc:title">
  E = mc<sup>2</sup>: The Most Urgent Problem of Our Time
</h2>



 In the examples given here the sup element is actually part of the
meaning of the literal, but there will be situations where the extra
mark-up means nothing, and can therefore be
ignored. In this situation an empty @datatype value can be used to
override the XML literal behaviour:



<p>You searched for
<strong>Einstein</strong>:</p>
<p about="http://dbpedia.org/resource/Albert_Einstein">
  <span property="foaf:name" datatype="">Albert
<strong>Einstein</strong></span>
  (b. March 14, 1879, d. April 18, 1955) was a German-born theoretical
physicist.
</p>



Although the rendering of this page has highlighted the term the user
searched for, setting @datatype to nothing ensures that the data is
interpreted as a plain literal,
giving the following triples:



<http://dbpedia.org/resource/Albert_Einstein> foaf:name "Albert
Einstein" .



Note that the value of this [XML Literal] is the exclusive
canonicalization of the RDFa element's value.

 Although the RDFa processing model requires visiting each element in
the tree, if the processor meets an [XML literal] then it
MUST NOT process any further down the tree. This is to prevent triples
being generated from mark-up that is not actually in the hierarchy.
For example, we might want to set the title of
something to some XHTML that itself includes RDFa:



<h2 property="dc:title">
  Example 3: <span about="#bbq"
typeof="cal:Vevent">...</span>
</h2>



 In this example the nested RDFa should not be parsed. This
effectively means that the presence of @property without @content will
inhibit any
further processing, so authors should watch out for stray attributes,
especially if they find that they are getting fewer triples than they
had expected.

6.3.2. URI object resolution

 Most of the rules governing the processing of objects that are
resources are to be found in the processing descriptions given above,
since they are important for establishing the subject. This
section aims to highlight general concepts, and anything that might
have been missed.

 One or more [URI object]s are needed when @rel or @rev is present.
Each attribute will cause
triples to be generated when used with @href, @resource or @src, or
with the subject value of any nested statement if
none of these attributes are present.

 @rel and @rev are essentially the inverse of each other; whilst @rel
establishes a relationship between the [current subject] as subject,
and the [current object resource] as the object, 
@rev does the exact opposite, and uses the [current object resource]
as the subject, and the [current subject] as the object.

6.3.2.1. Using @resource to set the object

RDFa provides the @resource attribute as a way to set the object of
statements. This is particularly useful when referring to resources
that are not themselves navigable
links:



<html>
  <head>
    <title>On Crime and Punishment</title>
    <base href="http://www.example.com/candp.xhtml" />
  </head>
  <body>
    <blockquote about="#q1" rel="dc:source"
resource="urn:ISBN:0140449132" >
      <p id="q1">
        Rodion Romanovitch! My dear friend! If you go on in this way
        you will go mad, I am positive! Drink, pray, if only a few
drops!
      </p>
    </blockquote>
  </body>
</html>



The blockquote element generates the following triple:



<http://www.example.com/candp.xhtml#q1>
  <http://purl.org/dc/elements/1.1/source>
<urn:ISBN:0140449132> .



6.3.2.2. Using @href

 If no @resource is present, then @href is next in priority order, for
setting the object.

When a predicate has been expressed using @rel, the @href on the [RDFa
statement]'s element is used to identify the object with a [URI
reference]. Its type is a URI:



<link about="mailto:john@example.org"
      rel="foaf:knows" href="mailto:sue@example.org" />



It's also possible to use both @rel and @rev at the same time on an
element. This is particularly useful when two things stand in two
different
relationships with each other, for example when a picture is taken by
Mark, but that picture also depicts him:



<img src="photo1.jpg" rel="dc:creator" rev="foaf:img"
   href="http://www.blogger.com/profile/1109404" />



which then yields two triples:



<photo1.jpg> 
  dc:creator <http://www.blogger.com/profile/1109404> .
<http://www.blogger.com/profile/1109404> 
  foaf:img <photo1.jpg> .



6.3.2.3. Incomplete triples

When a triple predicate has been expressed using @rel or @rev, but no
@href, @src, or @resource exists on the same element, there is a
'hanging rel'. This causes the current subject and all possible
predicates (with an indicator of whether they are 'forwards, i.e.,
@rel values, or not, i.e., @rev values), to be stored as 'incomplete
triples' pending discovery of a subject that could be used to
'complete' those
triples.

This process is described in more detail in Completing 'Incomplete
Triples'.


7. CURIE Syntax Definition

This section is normative.

The key component of RDF is the URI, but these are usually long and
unwieldy. RDFa therefore supports a mechanism by which URIs can be
abbreviated, called 'compact URIs' or simply, CURIEs.

A CURIE is comprised of two components, a prefix and a reference. The
prefix is separated from the reference by a colon (:). In general use
it is possible to omit
the prefix, and so create a CURIE that makes use of the 'default
prefix' mapping; in RDFa the 'default prefix' mapping is
http://www.w3.org/1999/xhtml/vocab#. It's also usually possible
to omit both the prefix and the colon, and so create a CURIE that
contains just a reference which makes use of the 'no prefix' mapping.
However, RDFa does not define a 'no prefix' mapping,
meaning that this form of CURIE is not supported.

 The general syntax of a CURIE can be summarised as follows:


curie       :=   [ [ prefix ] ':' ] reference

prefix      :=   NCName

reference   :=   irelative-ref (as defined in [IRI])


 In some situations an attribute will allow either a CURIE, or a
normal URI. Since it is difficult to distinguish between CURIEs and
URIs, the CURIE syntax adds the notion of a [safe CURIE]. The syntax
is simply to surround the CURIE with square brackets:


safe_curie  :=   '[' curie ']'


 In normal evaluation of CURIEs the following context information
would need to be provided:


a set of mappings from prefixes to URIs;

a mapping to use with the default prefix (for example, :p);

a mapping to use when there is no prefix (for example, p);

a mapping to use with the '_' prefix, which is used to generate unique
identifiers (for example, _:p).


 In RDFa these values are defined as follows:


the set of mappings from prefixes to URIs is provided by the current
in-scope prefix declarations of the [current element] during
parsing;

the mapping to use with the default prefix is the current default
prefix mapping;

the mapping to use when there is no prefix is not defined, which
effectively prohibits the use of CURIEs that do not contain a colon;

the mapping to use with the '_' prefix, is not explicitly stated, but
since it is used to generate [bnode]s, its implementation needs to be
compatible with the RDF definition.


A CURIE is a representation of a full URI. This URI is obtained by
taking the currently in-scope mapping that is associated with prefix,
and concatenating it with
the reference. The resulting URI MUST be a syntactically valid IRI
[IRI]. For a more detailed explanation see 
CURIE and URI Processing. Note that while the lexical space of a CURIE
is as defined in curie above, the value space is the set of IRIs.


8. XHTML+RDFa Definition

This section is normative.

The XHTML+RDFa document type is a fully functional document type with
rich semantics. It is a superset of [XHTML11].

The XHTML+RDFa 1.0 document type is made up of the following XHTML
modules. The elements, attributes, and content models associated with
these modules are defined in "XHTML Modularization" [XHTMLMOD]. The
elements are listed here for information purposes, but the definitions
in "XHTML Modularization" should be considered authoritative. In the
on-line version of this document, the module names in the list below
link into the definitions of the modules within the current versions
of "XHTML Modularization".


Structure Module

body, head, html, title

Text Module

abbr, acronym, address, blockquote, br, cite, code, dfn, div, em, h1,
h2, h3, h4, h5, h6, kbd, p, pre, q, samp, span, strong, var

Hypertext Module

a, and @href is available on all elements.

List Module

dl, dt, dd, ol, ul, li

Object Module

object, param

Presentation Module

b, big, hr, i, small, sub, sup, tt

Edit Module

del, ins

Bidirectional Text Module

bdo

Forms Module

button, fieldset, form, input, label, legend, select, optgroup,
option, textarea

Table Module

caption, col, colgroup, table, tbody, td, tfoot, th, thead, tr

Image Module

img

Client-side Image Map Module

area, map

Server-side Image Map Module

Attribute ismap on img

Intrinsic Events Module

Events attributes

Metainformation Module

meta

Scripting Module

noscript, script

Stylesheet Module

style element

Style Attribute Module Deprecated

@style

Target Module

@target

Link Module

link

Base Module

base

Metainformation Attributes Module

@about, @content, @datatype, @typeof, @property, @rel, @resource, @rev


XHTML+RDFa also uses the Ruby Annotation module as defined in [RUBY]:


Ruby Annotation Module

ruby, rbc, rtc, rb, rt, rp


There are no additional definitions required by this document type. An
implementation of this document type as an  XML DTD is defined in
Appendix A.


9. Metainformation Attributes Module

This section is normative.

The Metainformation Attributes Module defines the Metainformation
attribute collection. This collection allows elements to be annotated
with metadata throughout an XHTML-family
document. When this module is included in a markup language, this
collection is added to the Common attribute collection as defined in
[XHTMLMOD].

9.1. Datatypes

Some of the attributes in this section use the following datatypes:



Data type
Description



CURIE
A Compact URI or curie.



CURIEs
A whitespace separated list of CURIEs.



URIorSafeCURIE
A URI or safe_curie.



Note that a specification of these data types in XML DTD and XML
Schema is available in Appendix B.

9.2. Metainformation Attributes Collection

The following attributes are included in the attribute collection, and
take values in the associated datatype:




Attributes
Notes





about (URIorSafeCURIE)
 



content (CDATA)
 



datatype (CURIE)
If not specified, then the default value is string as defined in
[XMLSCHEMA].



typeof (CURIEs)
 



property (CURIEs)
 



rel (reserved word | CURIE)+
See the reserved values list in @rel/@rev Attribute Values



resource (URIorSafeCURIE)
 



rev (reserved word | CURIE)+
See the reserved values list in @rel/@rev attribute values




An implementation of this module can be found in Appendix A.

9.3. @rel/@rev attribute values

The list of reserved values for @rel and @rev are:


alternate

Designates alternate versions for a resource.

appendix

Refers to a resource serving as an appendix in a collection.

bookmark

Refers to a bookmark. A bookmark is a link to a key entry point within
an extended document. The @title attribute may be used, for example,
to label the bookmark. Note
that several bookmarks may be defined for a document.

cite


Refers to a resource that defines a citation. In the following
example, the cite is used to reference the book from which the
quotation is taken:


cite as book reference


As Gandalf the White said in 
<span rel="cite"
resource="http://www.example.com/books/the_two_towers">
    The Two Towers
</span>,
<quote xml:lang="en">"The hospitality of 
your hall is somewhat lessened of late, Theoden King."</quote>



which would generate the following triples:



<> xhv:cite <http://www.example.com/books/the_two_towers>
.



cite is also useful for referencing specifications: 


cite to reference another specification


More information can be found in 
<span rel="cite"
resource="http://www.w3.org/TR/REC-xml">[XML]</cite>.



which would generate the following triples:



<> xhv:cite <http://www.w3.org/TR/REC-xml> .




chapter

Refers to a resource serving as a chapter in a collection.

contents

Refers to a resource serving as a table of contents.

copyright

Refers to a copyright statement for the resource.

first

Refers to the first item in a collection (see also start and top).

glossary

Refers to a resource providing a glossary of terms.

help

Refers to a resource offering help (more information, links to other
sources of information, etc.)

icon

Refers to a resource that represents an icon.

index

Refers to a resource providing an index.

last

Refers to the last resource in a collection of resources.

license

Refers to a resource that defines the license associated with a
resource.

meta

Refers to a resource that provides metadata, for instance in RDF.

next

Refers to the next resource (after the current one) in an ordered
collection.

p3pv1

Refers to a P3P Policy Reference File. See [P3P].

prev

Refers to the previous resource (before the current one) in an ordered
collection.

role

Indicates the purpose of the resource. For some possible values, see
[XHTMLVOCAB].

section

Refers to a resource serving as a section in a collection.

stylesheet

Refers to a resource acting as a stylesheet for a resource.

subsection

Refers to a resource serving as a subsection in a collection.

start

Refers to the first resource in a collection of resources. A typical
use case might be a collection of chapters in a book.

top

Synonym for start.

up

Refers to the resource "above" in a hierarchically structured set.



A. XHTML+RDFa DTD

This appendix is normative.

This appendix includes an implementation of the XHTML+RDFa 1.0
language as an XML DTD. It is implemented by combining the XHTML 1.1
DTD with the XHTML Metainformation Attribute Module. This is
done by using a content model module, and then a driver module. There
are direct links to the various files, and the files are also
contained in the "Gzip'd TAR" and "Zip" archives linked to at the
top of this document. Please note that the files targeted by the
"latest version" links may change slowly over time. See the W3C XHTML2
Working Group home page for more information.

A.1. XHTML Metainformation Attributes Module

You can download this version of this file from
http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/DTD/xhtml-metaAttributes-1.mod.
The latest version
is available at
http://www.w3.org/MarkUp/DTD/xhtml-metaAttributes-1.mod.


<!--
......................................................................
-->
<!-- XHTML MetaAttributes Module 
......................................... -->
<!-- file: xhtml-metaAttributes-1.mod

     This is XHTML-RDFa, modules to annotate XHTML family documents.
     Copyright 2007-2008 W3C (MIT, ERCIM, Keio), All Rights Reserved.
     Revision: $Id: Overview.html,v 1.1 2008/10/13 15:17:31 swick Exp
$

     This DTD module is identified by the PUBLIC and SYSTEM
identifiers:

       PUBLIC "-//W3C//ENTITIES XHTML MetaAttributes 1.0//EN"
       SYSTEM
"http://www.w3.org/MarkUp/DTD/xhtml-metaAttributes-1.mod"

     Revisions:
     (none)
    
.......................................................................
-->

<!ENTITY % XHTML.global.attrs.prefixed "IGNORE" >

<!-- Placeholder Compact URI-related types -->
<!ENTITY % CURIE.datatype "CDATA" >
<!ENTITY % CURIEs.datatype "CDATA" >
<!ENTITY % SafeCURIE.datatype "CDATA" >
<!ENTITY % SafeCURIEs.datatype "CDATA" >
<!ENTITY % URIorSafeCURIE.datatype "CDATA" >
<!ENTITY % URIorSafeCURIEs.datatype "CDATA" >

<!-- Common Attributes

     This module declares a collection of meta-information related 
     attributes.

     %NS.decl.attrib; is declared in the XHTML Qname module.

     This file also includes declarations of "global" versions of the 
     attributes.  The global versions of the attributes are for use on

     elements in other namespaces.  
-->

<!ENTITY % about.attrib
     "about        %URIorSafeCURIE.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.about.attrib
     "%XHTML.prefix;:about           %URIorSafeCURIE.datatype;       
#IMPLIED"
>
]]>

<!ENTITY % typeof.attrib
     "typeof        %CURIEs.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.typeof.attrib
     "%XHTML.prefix;:typeof           %CURIEs.datatype;       
#IMPLIED"
>
]]>

<!ENTITY % property.attrib
     "property        %CURIEs.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.property.attrib
     "%XHTML.prefix;:property           %CURIEs.datatype;       
#IMPLIED"
>
]]>

<!ENTITY % resource.attrib
     "resource        %URIorSafeCURIE.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.resource.attrib
     "%XHTML.prefix;:resource           %URIorSafeCURIE.datatype;     
  #IMPLIED"
>
]]>

<!ENTITY % content.attrib
     "content        CDATA             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.content.attrib
     "%XHTML.prefix;:content           CDATA        #IMPLIED"
>
]]>

<!ENTITY % datatype.attrib
     "datatype        %CURIE.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.datatype.attrib
     "%XHTML.prefix;:datatype           %CURIE.datatype;       
#IMPLIED"
>
]]>

<!ENTITY % rel.attrib
     "rel        %CURIEs.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.rel.attrib
     "%XHTML.prefix;:rel           %CURIEs.datatype;        #IMPLIED"
>
]]>

<!ENTITY % rev.attrib
     "rev        %CURIEs.datatype;             #IMPLIED"
>

<![%XHTML.global.attrs.prefixed;[
<!ENTITY % XHTML.global.rev.attrib
     "%XHTML.prefix;:rev           %CURIEs.datatype;        #IMPLIED"
>
]]>

<!ENTITY % Metainformation.extra.attrib "" >

<!ENTITY % Metainformation.attrib
     "%about.attrib;
      %content.attrib;
      %datatype.attrib;
      %typeof.attrib;
      %property.attrib;
      %rel.attrib;
      %resource.attrib;
      %rev.attrib;
      %Metainformation.extra.attrib;"
>

<!ENTITY % XHTML.global.metainformation.extra.attrib "" >

<![%XHTML.global.attrs.prefixed;[

<!ENTITY % XHTML.global.metainformation.attrib
     "%XHTML.global.about.attrib;
      %XHTML.global.content.attrib;
      %XHTML.global.datatype.attrib;
      %XHTML.global.typeof.attrib;
      %XHTML.global.property.attrib;
      %XHTML.global.rel.attrib;
      %XHTML.global.resource.attrib;
      %XHTML.global.rev.attrib;
      %XHTML.global.metainformation.extra.attrib;"
>
]]>

<!ENTITY % XHTML.global.metainformation.attrib "" >


<!-- end of xhtml-metaAttributes-1.mod -->



A.2. XHTML+RDFa Content Model Module

You can download this version of this file from
http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/DTD/xhtml-rdfa-model-1.mod.
The latest version is
available at http://www.w3.org/MarkUp/DTD/xhtml-rdfa-model-1.mod.


<!--
.......................................................................
-->
<!-- XHTML+RDFa Document Model Module 
..................................... -->
<!-- file: xhtml-rdfa-model-1.mod

     This is XHTML+RDFa.
     Copyright 1998-2008 W3C (MIT, ERCIM, Keio), All Rights Reserved.
     Revision: $Id: Overview.html,v 1.1 2008/10/13 15:17:31 swick Exp
$ SMI

     This DTD module is identified by the PUBLIC and SYSTEM
identifiers:

       PUBLIC "-//W3C//ENTITIES XHTML+RDFa Document Model 1.0//EN"
       SYSTEM "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-model-1.mod"

     Revisions:
     (none)
    
.......................................................................
-->

<!-- XHTML+RDFa Document Model

     This module describes the groupings of elements that make up
     common content models for XHTML elements.

     XHTML has three basic content models:

         %Inline.mix;  character-level elements
         %Block.mix;   block-like elements, eg., paragraphs and lists
         %Flow.mix;    any block or inline elements

     Any parameter entities declared in this module may be used
     to create element content models, but the above three are
     considered 'global' (insofar as that term applies here).

     The reserved word '#PCDATA' (indicating a text string) is now
     included explicitly with each element declaration that is
     declared as mixed content, as XML requires that this token
     occur first in a content model specification.
-->
<!-- Extending the Model

     While in some cases this module may need to be rewritten to
     accommodate changes to the document model, minor extensions
     may be accomplished by redeclaring any of the three *.extra;
     parameter entities to contain extension element types as follows:

         %Misc.extra;    whose parent may be any block or
                         inline element.

         %Inline.extra;  whose parent may be any inline element.

         %Block.extra;   whose parent may be any block element.

     If used, these parameter entities must be an OR-separated
     list beginning with an OR separator ("|"), eg., "| a | b | c"

     All block and inline *.class parameter entities not part
     of the *struct.class classes begin with "| " to allow for
     exclusion from mixes.
-->

<!-- ..............  Optional Elements in head  ..................
-->

<!ENTITY % HeadOpts.mix
     "( %script.qname; | %style.qname; | %meta.qname;
      | %link.qname; | %object.qname; )*"
>

<!-- .................  Miscellaneous Elements  ..................
-->

<!-- ins and del are used to denote editing changes
-->
<!ENTITY % Edit.class "| %ins.qname; | %del.qname;" >

<!-- script and noscript are used to contain scripts
     and alternative content
-->
<!ENTITY % Script.class "| %script.qname; | %noscript.qname;" >

<!ENTITY % Misc.extra "" >

<!-- These elements are neither block nor inline, and can
     essentially be used anywhere in the document body.
-->
<!ENTITY % Misc.class
     "%Edit.class;
      %Script.class;
      %Misc.extra;"
>

<!-- ....................  Inline Elements  ......................
-->

<!ENTITY % InlStruct.class "%br.qname; | %span.qname;" >

<!ENTITY % InlPhras.class
     "| %em.qname; | %strong.qname; | %dfn.qname; | %code.qname;
      | %samp.qname; | %kbd.qname; | %var.qname; | %cite.qname;
      | %abbr.qname; | %acronym.qname; | %q.qname;" >

<!ENTITY % InlPres.class
     "| %tt.qname; | %i.qname; | %b.qname; | %big.qname;
      | %small.qname; | %sub.qname; | %sup.qname;" >

<!ENTITY % I18n.class "| %bdo.qname;" >

<!ENTITY % Anchor.class "| %a.qname;" >

<!ENTITY % InlSpecial.class
     "| %img.qname; | %map.qname;
      | %object.qname;" >

<!ENTITY % InlForm.class
     "| %input.qname; | %select.qname; | %textarea.qname;
      | %label.qname; | %button.qname;" >

<!ENTITY % Inline.extra "" >

<!ENTITY % Ruby.class "| %ruby.qname;" >

<!-- %Inline.class; includes all inline elements,
     used as a component in mixes
-->
<!ENTITY % Inline.class
     "%InlStruct.class;
      %InlPhras.class;
      %InlPres.class;
      %I18n.class;
      %Anchor.class;
      %InlSpecial.class;
      %InlForm.class;
      %Ruby.class;
      %Inline.extra;"
>

<!-- %InlNoRuby.class; includes all inline elements
     except ruby, used as a component in mixes
-->
<!ENTITY % InlNoRuby.class
     "%InlStruct.class;
      %InlPhras.class;
      %InlPres.class;
      %I18n.class;
      %Anchor.class;
      %InlSpecial.class;
      %InlForm.class;
      %Inline.extra;"
>

<!-- %NoRuby.content; includes all inlines except ruby
-->
<!ENTITY % NoRuby.content
     "( #PCDATA
      | %InlNoRuby.class;
      %Misc.class; )*"
>

<!-- %InlNoAnchor.class; includes all non-anchor inlines,
     used as a component in mixes
-->
<!ENTITY % InlNoAnchor.class
     "%InlStruct.class;
      %InlPhras.class;
      %InlPres.class;
      %I18n.class;
      %InlSpecial.class;
      %InlForm.class;
      %Ruby.class;
      %Inline.extra;"
>

<!-- %InlNoAnchor.mix; includes all non-anchor inlines
-->
<!ENTITY % InlNoAnchor.mix
     "%InlNoAnchor.class;
      %Misc.class;"
>

<!-- %Inline.mix; includes all inline elements, including
%Misc.class;
-->
<!ENTITY % Inline.mix
     "%Inline.class;
      %Misc.class;"
>

<!-- .....................  Block Elements  ......................
-->

<!-- In the HTML 4.0 DTD, heading and list elements were included
     in the %block; parameter entity. The %Heading.class; and
     %List.class; parameter entities must now be included explicitly
     on element declarations where desired.
-->

<!ENTITY % Heading.class
     "%h1.qname; | %h2.qname; | %h3.qname;
      | %h4.qname; | %h5.qname; | %h6.qname;" >

<!ENTITY % List.class "%ul.qname; | %ol.qname; | %dl.qname;" >

<!ENTITY % Table.class "| %table.qname;" >

<!ENTITY % Form.class  "| %form.qname;" >

<!ENTITY % Fieldset.class  "| %fieldset.qname;" >

<!ENTITY % BlkStruct.class "%p.qname; | %div.qname;" >

<!ENTITY % BlkPhras.class
     "| %pre.qname; | %blockquote.qname; | %address.qname;" >

<!ENTITY % BlkPres.class "| %hr.qname; " >

<!ENTITY % BlkSpecial.class
     "%Table.class;
      %Form.class;
      %Fieldset.class;"
>

<!ENTITY % Block.extra "" >

<!-- %Block.class; includes all block elements,
     used as an component in mixes
-->
<!ENTITY % Block.class
     "%BlkStruct.class;
      %BlkPhras.class;
      %BlkPres.class;
      %BlkSpecial.class;
      %Block.extra;"
>

<!-- %Block.mix; includes all block elements plus %Misc.class;
-->
<!ENTITY % Block.mix
     "%Heading.class;
      | %List.class;
      | %Block.class;
      %Misc.class;"
>

<!-- ................  All Content Elements  ..................
-->

<!-- %Flow.mix; includes all text content, block and inline
-->
<!ENTITY % Flow.mix
     "%Heading.class;
      | %List.class;
      | %Block.class;
      | %Inline.class;
      %Misc.class;"
>

<!-- end of xhtml-rdfa-model-1.mod -->



A.3. XHTML+RDFa Driver Module

You can download this version of this file from
http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/DTD/xhtml-rdfa-1.dtd.
The latest version is available at
http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd.


<!--
.......................................................................
-->
<!-- XHTML 1.1 + RDFa DTD 
................................................. -->
<!-- file: xhtml-rdfa-1.dtd
-->

<!-- XHTML 1.1 + RDFa DTD

     This is an example markup language combining XHTML 1.1 and the
RDFa
     modules.

     XHTML+RDFa
     Copyright 1998-2008 World Wide Web Consortium
        (Massachusetts Institute of Technology, European Research
Consortium
         for Informatics and Mathematics, Keio University).
         All Rights Reserved.

     Permission to use, copy, modify and distribute the XHTML DTD and
its 
     accompanying documentation for any purpose and without fee is
hereby 
     granted in perpetuity, provided that the above copyright notice
and 
     this paragraph appear in all copies.  The copyright holders make
no 
     representation about the suitability of the DTD for any purpose.

     It is provided "as is" without expressed or implied warranty.

-->
<!-- This is the driver file for version 1 of the XHTML + RDFa DTD.

     Please use this public identifier to identify it:

         "-//W3C//DTD XHTML+RDFa 1.0//EN"
-->
<!ENTITY % XHTML.version  "XHTML+RDFa 1.0" >

<!-- Use this URI to identify the default namespace:

         "http://www.w3.org/1999/xhtml"

     See the Qualified Names module for information
     on the use of namespace prefixes in the DTD.

     Note that XHTML namespace elements are not prefixed by default,
     but the XHTML namespace prefix is defined as "xhtml" so that
     other markup languages can extend this one and use the XHTML
     prefixed global attributes if required.

-->
<!ENTITY % NS.prefixed "IGNORE" >
<!ENTITY % XHTML.prefix "xhtml" >

<!-- Be sure to include prefixed global attributes - we don't need
     them, but languages that extend XHTML 1.1 might.
-->
<!ENTITY % XHTML.global.attrs.prefixed "INCLUDE" >

<!-- Reserved for use with the XLink namespace:
-->
<!ENTITY % XLINK.xmlns "" >
<!ENTITY % XLINK.xmlns.attrib "" >

<!-- For example, if you are using XHTML 1.1 directly, use the
public
     identifier in the DOCTYPE declaration, with the namespace
declaration
     on the document element to identify the default namespace:

       <?xml version="1.0"?>
       <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
                            
"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
       <html xmlns="http://www.w3.org/1999/xhtml"
             xml:lang="en">
       ...
       </html>

     Revisions:
     (none)
-->

<!-- reserved for future use with document profiles -->
<!ENTITY % XHTML.profile  "" >

<!-- ensure XHTML Notations are disabled -->
<!ENTITY % xhtml-notations.module "IGNORE" >

<!-- Bidirectional Text features
     This feature-test entity is used to declare elements
     and attributes used for bidirectional text support.
-->
<!ENTITY % XHTML.bidi  "INCLUDE" >

<!--
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
-->

<!-- Pre-Framework Redeclaration placeholder  ....................
-->
<!-- this serves as a location to insert markup declarations
     into the DTD prior to the framework declarations.
-->
<!ENTITY % xhtml-prefw-redecl.module "IGNORE" >
<!ENTITY % xhtml-prefw-redecl.mod "" >
<![%xhtml-prefw-redecl.module;[
%xhtml-prefw-redecl.mod;
<!-- end of xhtml-prefw-redecl.module -->]]>

<!-- we need the datatypes now -->
<!ENTITY % xhtml-datatypes.module "INCLUDE" >
<![%xhtml-datatypes.module;[
<!ENTITY % xhtml-datatypes.mod
     PUBLIC "-//W3C//ENTITIES XHTML Datatypes 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-datatypes-1.mod" >
%xhtml-datatypes.mod;]]>

<!-- bring in the RDFa attributes cause we need them in Common
-->
<!ENTITY % xhtml-metaAttributes.module "INCLUDE" >
<![%xhtml-metaAttributes.module;[
<!ENTITY % xhtml-metaAttributes.mod
     PUBLIC "-//W3C//ENTITIES XHTML MetaAttributes 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-metaAttributes-1.mod"
>
%xhtml-metaAttributes.mod;]]>

<!ENTITY % xhtml-events.module "INCLUDE" >

<!ENTITY % Common.extra.attrib
   "href         %URI.datatype;           #IMPLIED
    %Metainformation.attrib;"
>

<!-- Inline Style Module  ........................................
-->
<!ENTITY % xhtml-inlstyle.module "INCLUDE" >
<![%xhtml-inlstyle.module;[
<!ENTITY % xhtml-inlstyle.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Inline Style 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-inlstyle-1.mod" >
%xhtml-inlstyle.mod;]]>

<!-- declare Document Model module instantiated in framework
-->
<!ENTITY % xhtml-model.mod
     PUBLIC "-//W3C//ENTITIES XHTML+RDFa Document Model 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-model-1.mod" >

<!-- Modular Framework Module (required) .........................
-->
<!ENTITY % xhtml-framework.module "INCLUDE" >
<![%xhtml-framework.module;[
<!ENTITY % xhtml-framework.mod
     PUBLIC "-//W3C//ENTITIES XHTML Modular Framework 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-framework-1.mod" >
%xhtml-framework.mod;]]>

<!-- Post-Framework Redeclaration placeholder  ...................
-->
<!-- this serves as a location to insert markup declarations
     into the DTD following the framework declarations.
-->
<!ENTITY % xhtml-postfw-redecl.module "IGNORE" >
<!ENTITY % xhtml-postfw-redecl.mod "">
<![%xhtml-postfw-redecl.module;[
%xhtml-postfw-redecl.mod;
<!-- end of xhtml-postfw-redecl.module -->]]>



<!-- Text Module (Required)  .....................................
-->
<!ENTITY % xhtml-text.module "INCLUDE" >
<![%xhtml-text.module;[
<!ENTITY % xhtml-text.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Text 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-text-1.mod" >
%xhtml-text.mod;]]>

<!-- Hypertext Module (required) .................................
-->
<!ENTITY % a.attlist  "IGNORE" >
<!ENTITY % xhtml-hypertext.module "INCLUDE" >
<![%xhtml-hypertext.module;[
<!ENTITY % xhtml-hypertext.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Hypertext 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-hypertext-1.mod" >
%xhtml-hypertext.mod;]]>
<!ATTLIST %a.qname;
      %Common.attrib;
      charset      %Charset.datatype;       #IMPLIED
      type         %ContentType.datatype;   #IMPLIED
      hreflang     %LanguageCode.datatype;  #IMPLIED
      accesskey    %Character.datatype;     #IMPLIED
      tabindex     %Number.datatype;        #IMPLIED
>

<!-- Lists Module (required)  ....................................
-->
<!ENTITY % xhtml-list.module "INCLUDE" >
<![%xhtml-list.module;[
<!ENTITY % xhtml-list.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Lists 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-list-1.mod" >
%xhtml-list.mod;]]>

<!--
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
-->

<!-- Edit Module  ................................................
-->
<!ENTITY % xhtml-edit.module "INCLUDE" >
<![%xhtml-edit.module;[
<!ENTITY % xhtml-edit.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Editing Elements 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-edit-1.mod" >
%xhtml-edit.mod;]]>

<!-- BIDI Override Module  .......................................
-->
<!ENTITY % xhtml-bdo.module "%XHTML.bidi;" >
<![%xhtml-bdo.module;[
<!ENTITY % xhtml-bdo.mod
     PUBLIC "-//W3C//ELEMENTS XHTML BIDI Override Element 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-bdo-1.mod" >
%xhtml-bdo.mod;]]>

<!-- Ruby Module  ................................................
-->
<!ENTITY % Ruby.common.attlists "INCLUDE" >
<!ENTITY % Ruby.common.attrib "%Common.attrib;" >
<!ENTITY % xhtml-ruby.module "INCLUDE" >
<![%xhtml-ruby.module;[
<!ENTITY % xhtml-ruby.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Ruby 1.0//EN"
            "http://www.w3.org/TR/ruby/xhtml-ruby-1.mod" >
%xhtml-ruby.mod;]]>

<!-- Presentation Module  ........................................
-->
<!ENTITY % xhtml-pres.module "INCLUDE" >
<![%xhtml-pres.module;[
<!ENTITY % xhtml-pres.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Presentation 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-pres-1.mod" >
%xhtml-pres.mod;]]>

<!ENTITY % link.attlist  "IGNORE" >
<!-- Link Element Module  ........................................
-->
<!ENTITY % xhtml-link.module "INCLUDE" >
<![%xhtml-link.module;[
<!ENTITY % xhtml-link.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Link Element 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-link-1.mod" >
%xhtml-link.mod;]]>

<!ATTLIST %link.qname;
      %Common.attrib;
      charset      %Charset.datatype;       #IMPLIED
      hreflang     %LanguageCode.datatype;  #IMPLIED
      type         %ContentType.datatype;   #IMPLIED
      media        %MediaDesc.datatype;     #IMPLIED
>

<!-- Document Metainformation Module  ............................
-->
<!ENTITY % meta.attlist  "IGNORE" >
<!ENTITY % xhtml-meta.module "INCLUDE" >
<![%xhtml-meta.module;[
<!ENTITY % xhtml-meta.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Metainformation 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-meta-1.mod" >
%xhtml-meta.mod;]]>
<!ATTLIST %meta.qname;
      %Common.attrib;
      http-equiv   NMTOKEN                  #IMPLIED
      name         NMTOKEN                  #IMPLIED
      scheme       CDATA                    #IMPLIED
>

<!-- Base Element Module  ........................................
-->
<!ENTITY % xhtml-base.module "INCLUDE" >
<![%xhtml-base.module;[
<!ENTITY % xhtml-base.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Base Element 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-base-1.mod" >
%xhtml-base.mod;]]>

<!-- Scripting Module  ...........................................
-->
<!ENTITY % script.attlist  "IGNORE" >
<!ENTITY % xhtml-script.module "INCLUDE" >
<![%xhtml-script.module;[
<!ENTITY % xhtml-script.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Scripting 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-script-1.mod" >
%xhtml-script.mod;]]>

<!ATTLIST %script.qname;
      %XHTML.xmlns.attrib;
      %id.attrib;
      %Metainformation.attrib;
      href         %URI.datatype;           #IMPLIED
      xml:space    ( preserve )             #FIXED 'preserve'
      charset      %Charset.datatype;       #IMPLIED
      type         %ContentType.datatype;   #REQUIRED
      src          %URI.datatype;           #IMPLIED
      defer        ( defer )                #IMPLIED
>

<!-- Style Sheets Module  .........................................
-->
<!ENTITY % style.attlist  "IGNORE" >
<!ENTITY % xhtml-style.module "INCLUDE" >
<![%xhtml-style.module;[
<!ENTITY % xhtml-style.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Style Sheets 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-style-1.mod" >
%xhtml-style.mod;]]>
<!ATTLIST %style.qname;
      %XHTML.xmlns.attrib;
      %id.attrib;
      %title.attrib;
      %I18n.attrib;
      %Metainformation.attrib;
      href         %URI.datatype;           #IMPLIED
      xml:space    ( preserve )             #FIXED 'preserve'
      type         %ContentType.datatype;   #REQUIRED
      media        %MediaDesc.datatype;     #IMPLIED
>

<!-- Image Module  ...............................................
-->
<!ENTITY % xhtml-image.module "INCLUDE" >
<![%xhtml-image.module;[
<!ENTITY % xhtml-image.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Images 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-image-1.mod" >
%xhtml-image.mod;]]>

<!-- Client-side Image Map Module  ...............................
-->
<!ENTITY % area.attlist  "IGNORE" >

<!ENTITY % xhtml-csismap.module "INCLUDE" >
<![%xhtml-csismap.module;[
<!ENTITY % xhtml-csismap.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Client-side Image Maps 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-csismap-1.mod" >
%xhtml-csismap.mod;]]>

<!ATTLIST %area.qname;
      %Common.attrib;
      shape        %Shape.datatype;         'rect'
      coords       %Coords.datatype;        #IMPLIED
      nohref       ( nohref )               #IMPLIED
      alt          %Text.datatype;          #REQUIRED
      tabindex     %Number.datatype;        #IMPLIED
      accesskey    %Character.datatype;     #IMPLIED
>

<!-- Server-side Image Map Module  ...............................
-->
<!ENTITY % xhtml-ssismap.module "INCLUDE" >
<![%xhtml-ssismap.module;[
<!ENTITY % xhtml-ssismap.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Server-side Image Maps 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-ssismap-1.mod" >
%xhtml-ssismap.mod;]]>

<!-- Param Element Module  .......................................
-->
<!ENTITY % param.attlist  "IGNORE" >
<!ENTITY % xhtml-param.module "INCLUDE" >
<![%xhtml-param.module;[
<!ENTITY % xhtml-param.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Param Element 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-param-1.mod" >
%xhtml-param.mod;]]>

<!ATTLIST %param.qname;
      %XHTML.xmlns.attrib;
      %id.attrib;
      %Metainformation.attrib;
      href         %URI.datatype;           #IMPLIED
      name         CDATA                    #REQUIRED
      value        CDATA                    #IMPLIED
      valuetype    ( data | ref | object )  'data'
      type         %ContentType.datatype;   #IMPLIED
>
<!-- Embedded Object Module  .....................................
-->
<!ENTITY % xhtml-object.module "INCLUDE" >
<![%xhtml-object.module;[
<!ENTITY % xhtml-object.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Embedded Object 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-object-1.mod" >
%xhtml-object.mod;]]>

<!-- Tables Module ...............................................
-->
<!ENTITY % xhtml-table.module "INCLUDE" >
<![%xhtml-table.module;[
<!ENTITY % xhtml-table.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Tables 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-table-1.mod" >
%xhtml-table.mod;]]>

<!-- Forms Module  ...............................................
-->
<!ENTITY % xhtml-form.module "INCLUDE" >
<![%xhtml-form.module;[
<!ENTITY % xhtml-form.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Forms 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-form-1.mod" >
%xhtml-form.mod;]]>

<!-- Target Attribute Module  ....................................
-->
<!ENTITY % xhtml-target.module "INCLUDE" >
<![%xhtml-target.module;[
<!ENTITY % xhtml-target.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Target 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-target-1.mod" >
%xhtml-target.mod;]]>

<!-- Legacy Markup ...............................................
-->
<!ENTITY % xhtml-legacy.module "IGNORE" >
<![%xhtml-legacy.module;[
<!ENTITY % xhtml-legacy.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Legacy Markup 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-legacy-1.mod" >
%xhtml-legacy.mod;]]>

<!-- Document Structure Module (required)  .......................
-->
<!ENTITY % html.attlist  "IGNORE" >
<!ENTITY % head.attlist  "IGNORE" >
<!ENTITY % title.attlist  "IGNORE" >
<!ENTITY % xhtml-struct.module "INCLUDE" >
<![%xhtml-struct.module;[
<!ENTITY % xhtml-struct.mod
     PUBLIC "-//W3C//ELEMENTS XHTML Document Structure 1.0//EN"
            "http://www.w3.org/MarkUp/DTD/xhtml-struct-1.mod" >
%xhtml-struct.mod;]]>
<!ENTITY % profile.attrib
     "profile      %URI.datatype;           '%XHTML.profile;'"
>
<!ENTITY % XHTML.version.attrib
     "version      %FPI.datatype;           #FIXED '%XHTML.version;'"
>
<!ATTLIST %html.qname;
      %Common.attrib;
      %XSI.schemaLocation.attrib;
      %XHTML.version.attrib;
>
<!ATTLIST %head.qname;
      %Common.attrib;
      %profile.attrib;
>
<!ATTLIST %title.qname;
      %Common.attrib;
>

<!-- end of XHTML-RDFa DTD 
................................................ -->
<!--
.......................................................................
-->



A.4. SGML Open Catalog Entry for XHTML+RDFa

This section contains the SGML Open Catalog-format definition
[CATALOG] of the public identifiers for XHTML+RDFa 1.0.

You can download this version of this file from
http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/DTD/xhtml-rdfa.cat.
The latest version is available at
http://www.w3.org/MarkUp/DTD/xhtml-rdfa.cat.


--
..........................................................................
--
-- File catalog 
............................................................ --

--  XHTML+RDFa Catalog Data File

    Revision:  $Revision: 1.1 $

    See "Entity Management", SGML Open Technical Resolution 9401 for
detailed
    information on supplying and using catalog data. This document is
available
    from OASIS at URL:

        <http://www.oasis-open.org/html/tr9401.html>
--

--
..........................................................................
--
-- SGML declaration associated with XHTML 
.................................. --

OVERRIDE YES

SGMLDECL "xml1.dcl"

--
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
--

-- XHTML+RDFa modules         
.............................................. --


PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"       "xhtml-rdfa-1.dtd"


PUBLIC "-//W3C//ENTITIES XHTML+RDFa Document Model 1.0//EN"     
"xhtml-rdfa-model-1.mod"

PUBLIC "-//W3C//ENTITIES XHTML MetaAttributes 1.0//EN"          
"xhtml-metaAttributes-1.mod"

-- End of catalog data 
..................................................... --
--
..........................................................................
--




B. CURIE Datatypes

This section is informative.

In order to facilitate the use of CURIEs in markup languages, this
specification defines some additional datatypes in the XHTML datatype
space
(http://www.w3.org/1999/xhtml/datatypes/). Markup languages that use
XHTML Modularization can find these normative definitions in the
Modularization support file "datatypes" for their
schema grammar:


DTD xhtml-datatypes.mod

XML Schema xhtml-datatypes.xsd


Specifically, the following datatypes are introduced:


CURIE

A single curie

CURIEs

A whitespace separated list of CURIEs

SafeCURIE

A single safe_curie

SafeCURIEs

A whitespace separated list of SafeCURIEs

URIorSafeCURIE

A URI or a SafeCURIE (since you need a SafeCURIE to disambiguate
between a common URI and a CURIE)

URIorSafeCURIEs

A whitespace separated list of URIorSafeCURIEs


B.1. XML Schema Definition

The following informative XML Schema definition for these datatypes is
included as an example:



<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
 xmlns:xs="http://www.w3.org/2001/XMLSchema"
 xmlns="http://www.w3.org/1999/xhtml/datatypes/"
 xmlns:xh11d="http://www.w3.org/1999/xhtml/datatypes/"
 targetNamespace="http://www.w3.org/1999/xhtml/datatypes/"
 elementFormDefault="qualified"
>
    <xs:simpleType name="CURIE">
        <xs:restriction base="xs:string">
            <xs:pattern value="(([\i-[:]][\c-[:]]*)?:)?.+" />
            <xs:minLength value="1"/>
        </xs:restriction>
    </xs:simpleType> 

    <xs:simpleType name="CURIEs">
        <xs:list itemType="xh11d:CURIE"/>
    </xs:simpleType>

    <xs:simpleType name="SafeCURIE">
        <xs:restriction base="xs:string">
            <xs:pattern value="\[(([\i-[:]][\c-[:]]*)?:)?.+\]"
/>
            <xs:minLength value="3"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="SafeCURIEs">
        <xs:list itemType="xh11d:SafeCURIE"/>
    </xs:simpleType>

    <xs:simpleType name="URIorSafeCURIE">
        <xs:union memberTypes="xs:anyURI xh11d:SafeCURIE" />
    </xs:simpleType>

    <xs:simpleType name="URIorSafeCURIEs">
        <xs:list itemType="xh11d:URIorSafeCURIE"/>
    </xs:simpleType>
</xs:schema>



B.2. XML DTD Definition

The following informative XML DTD definition for these datatypes is
included as an example:



<!ENTITY % CURIE.datatype "CDATA" >
<!ENTITY % CURIEs.datatype "CDATA" >
<!ENTITY % SafeCURIE.datatype "CDATA" >
<!ENTITY % SafeCURIEs.datatype "CDATA" >
<!ENTITY % URIorSafeCURIE.datatype "CDATA" >
<!ENTITY % URIorSafeCURIEs.datatype "CDATA" >




C. Deployment Advice

This section is informative.

Documents written using the markup language defined in this
specification can be validated using the DTD defined in Appendix A. If
a document author wants to
faciliate such validation, they may include the following declaration
at the top of their document:


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
    "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">


The XML Namespace document associated with the XHTML Family of markup
languages uses the mechanism for transforming XHTML+RDFa documents
into RDF as defined by [GRDDL]. Authors who want to be certain their
documents are transformable by all [GRDDL] processors may also include
a profile
attribute on the head element that includes a reference to the XHTML
vocabulary URI http://www.w3.org/1999/xhtml/vocab.


D. References

D.1. Related Specifications

This section is normative.


[IRI]

"Internationalized Resource Identifiers (IRI)", RFC 3987, M.Duerst, M.
Suignard January 2005.
Available at: http://www.ietf.org/rfc/rfc3987.txt

[P3P]

"The Platform for Privacy Preferences 1.0 (P3P1.0) Specification", W3C
Recommendation, L. Cranor 
et al., 16 April 2002.
Available at: http://www.w3.org/TR/2002/REC-P3P-20020416/

[RFC2119]

"Key words for use in RFCs to indicate requirement levels", RFC 2119,
S. Bradner, March 1997.
 Available at: http://www.rfc-editor.org/rfc/rfc2119.txt

[RFC3236]

"The 'application/xhtml+xml' Media Type", M. Baker, P. Stark, January
2002.
Available at: http://www.ietf.org/rfc/rfc3236.txt

[RUBY]

Ruby Annotation, W3C Recommendation, Marcin Sawicki, et al., 31 May
2001.
 See: http://www.w3.org/TR/2001/REC-ruby-20010531

[URI]

"Uniform Resource Identifier (URI): Generic Syntax", RFC 3986, T.
Berners-Lee, R. Fielding, L. Masinter, January 2005.
 Available at: http://www.ietf.org/rfc/rfc3986.txt

[XMLBASE]

"XML Base", W3C Recommendation, J. Marsh, ed., 27 June 2001.
Available at: http://www.w3.org/TR/2001/REC-xmlbase-20010627/

[XMLNS]

"Namespaces in XML", W3C Recommendation, T. Bray et al., 
eds., 14 January 1999.
Available at: http://www.w3.org/TR/1999/REC-xml-names-19990114

[XML-LANG]

"Extensible Markup Language (XML) 1.0 (Third Edition)", W3C
Recommendation, T. Bray et al.,
eds., 4 February 2004.
Available at: http://www.w3.org/TR/2004/REC-xml-20040204

[XHTMLMOD]

XHTML Modularization 1.1, W3C Recommendation, Shane McCarron, et al.,
8 October 2008
 See: http://www.w3.org/TR/2008/REC-xhtml-modularization-20081008

[XMLSCHEMA]

"XML Schema Part 1: Structures Second Edition", W3C Recommendation, H.
S. Thompson et
al., eds., 28 October 2004.
Available at: http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/
See also "XML Schema Part 2: Datatypes Second Edition", available at:
http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/


D.2. Other References

This section is informative.


[CATALOG]

Entity Management: OASIS Technical Resolution 9401:1997 (Amendment 2
to TR 9401), Paul Grosso, Chair, Entity Management
Subcommittee, SGML Open, 10 September 1997.
 See: http://www.oasis-open.org/html/a401.htm

[DBPEDIA]

DBPedia (See http://dbpedia.org/.)

[DC]

Dublin Core Metadata Initiative (DCMI) (See http://dublincore.org/.)

[FOAF-PROJECT]

The FOAF Project (See http://www.foaf-project.org.)

[GRDDL]

"Gleaning Resource Descriptions from Dialects of Languages (GRDDL),
W3C Recommendation, D. Connolly, ed., 11 September 2007.
Available at: http://www.w3.org/TR/2007/REC-grddl-20070911

[HTML4]

"HTML 4.01 Specification", W3C Recommendation, D. Raggett et al.,
eds., 24 December 1999.
Available at: http://www.w3.org/TR/1999/REC-html401-19991224

[MICROFORMATS]

See microformats.org.

[RDFHTML]

RDF-in-HTML Task Force (See
http://www.w3.org/2001/sw/BestPractices/HTML/.)

[RDFa Primer]

RDFa Primer 1.0 - Embedding Structured Data in Web Pages (see
http://www.w3.org/TR/xhtml-rdfa-primer/.)

[RDF-CONCEPTS]

Resource Description Framework (RDF): Concepts and Abstract Syntax
(See http://www.w3.org/TR/rdf-concepts/.)

[RDF-PRIMER]

RDF Primer (See http://www.w3.org/TR/rdf-primer/.)

[RDF-SYNTAX]

RDF/XML Syntax and Grammar (See
http://www.w3.org/TR/rdf-syntax-grammar/.)

[RDFTESTS-DATATYPES-TEST001]

datatypes/test001.nt (See
http://www.w3.org/2000/10/rdf-tests/rdfcore/datatypes/test001.nt.)

[RDFTESTS-RDFMS-XMLLANG-TEST006]

rdfms-xmllang/test006.nt (See
http://www.w3.org/2000/10/rdf-tests/rdfcore/rdfms-xmllang/test006.nt.)

[RELAXNG]

RELAX NG Home Page (See http://www.relaxng.org/.)

[SWD-WG]

Semantic Web Deployment Working Group (See
http://www.w3.org/2006/07/SWD/.)

[TURTLE]

Turtle: Terse RDF Triple Language, David Beckett, Tim Berners-Lee,
January 2008.
 See: http://www.w3.org/TeamSubmission/turtle/

[XHTML 1.1]

"XHTML 1.1 - Module-based XHTML", W3C Recommendation, M. Altheim, S.
McCarron, 31 May 2001.
Available at: http://www.w3.org/TR/2001/REC-xhtml11-20010531/.

[XHTML2-WG]

XHTML 2 Working Group (See http://www.w3.org/MarkUp/.)

[XHTMLMIME]

"XHTML Media Types", Masayasu Ishikawa, 1 August 2002.
Latest version available at: http://www.w3.org/TR/xhtml-media-types

[XHTMLVOCAB]

"XHTML Vocabulary", XHTML 2 Working Group.
Available at: http://www.w3.org/1999/xhtml/vocab



E. Change History

This section is informative.

2008-06-03: Added informative section on XHTML Fragments. Also ensured
that we say "namespace" when we mean XML Namespace, and "prefix" when
we mean the front part of a CURIE. [ShaneMcCarron]

2008-05-15: Moved section on bnode references in CURIEs into Chapter 5
(which is normative). Also fixed some term definitions that referred
to "document" to refer to "resource".
[ShaneMcCarron]

2008-05-12: Changed processing rules 4 and 5 to look for the presence
of @rel and @rev, rather than whether they have valid values. That is
checked later. [MarkBirbeck]

2008-05-09: Removed reference to "reserved values" in the context of
@about: about does not take reserved values. [ShaneMcCarron]

2008-05-08: Added informative reference to the XHTML Vocabulary
definition document. [ShaneMcCarron]

2008-05-01: Changed datatype name from URIorCURIE to URIorSafeCURIE.
Added datatype implementation in Appendix B. Added text about
preferring inline content to @content so you do not lose ability
to have rich markup. [ShaneMcCarron]

2008-04-29: Changed processing rules so as to allow the generation of
triples that have objects which are bnodes, even if those bnodes never
appear in a triple as a subject. [MarkBirbeck]

2008-04-28: The processing rules have been updated so that elements
that do not contain any RDFa attributes have no effect. At one point
this step omitted to check for 
@property, meaning that elements that contained only @property were
being ignored. [MarkBirbeck]

2008-04-03: Changed instanceof to @typeof. [ShaneMcCarron]

2008-01-23: Updated to reflect latest task-force thinking re- the
processing of legacy values in @rel and @rev. As part of this work,
made the
whole processing of CURIEs and URIs much clearer. [MarkBirbeck]

2008-01-03: Updated to reflect latest task-force thinking re- the
processing model, in particular regarding 'chaining', and the
behaviour of instanceof. [MarkBirbeck]

2007-10-19: Updated to reflect latest task-force thinking re:
processing model. Integrated XHTML Module definition and hybrid markup
language. Completed development as First Public Working Draft.
[ShaneMcCarron], [MarkBirbeck]

2007-09-04: Migrated to XHTML 2 Working Group Publication System.
Converted to a format that is consistent with REC-Track documents.
Updated to reflect current processing model. Added normative
definition of CURIEs. Started updating prose to be consistent with
current task force agremeents. [ShaneMcCarron], [StevenPemberton],
[MarkBirbeck]

2007-04-06: fixed some of the language to talk about "structure"
rather than metadata. Added note regarding space-separated values in
predicate-denoting attributes. [BenAdida]

2006-01-16: made the use of CURIE type for @rel, @rev, @property
consistent across document (particularly section 2.4
was erroneous). [BenAdida]


F. Acknowledgments

This section is informative.

At the time of publication, the members of the Semantic Web Deployment
Working Group were:


Ben Adida, Creative Commons (RDFa Task Force Convener)

Thomas Baker, Kompetenzzentrum Interoperable Metadaten (KIM)
(Co-Chair)

Sean Bechhofer, University of Manchester

Diego Berrueta, Fundación CTIC

Jeremy Carroll, TopQuadrant

Michael Hausenblas, K-Space

Antoine Isaac, Vrije Universiteit

Elisa Kendall, Sandpiper Software, Inc.

Alistair Miles, Science & Technology Facilities Council

Vit Novacek, DERI Galway at the National University of Ireland

Simone Onofri, International Webmasters Association / HTML Writers
Guild (IWA-HWG)

Jon Phipps, Invited Expert

Clay Redding, Library of Congress

Quentin Reul, University of Aberdeen

Daniel Rubin, Stanford University

Guus Schreiber, Vrije Universiteit (Co-Chair)

Margherita Sini, UN Food and Agriculture Organization (Invited Expert)

Manu Sporny, Digital Bazaar (Invited Expert)

Ed Summers, Library of Congress

Ralph Swick, W3C


At the time of publication, the members in the XHTML 2 Working Group
were:


Roland Merrick, IBM (XHTML 2 Working Group Co-Chair)

Steven Pemberton, CWI (XHTML 2 Working Group
Co-Chair)

Mark Birbeck, webBackplane (Invited Expert)

Susan Borgrink, Progeny Systems

Christina Bottomley, Society for Technical Communication (STC)

Alessio Cartocci, International Webmasters Association / HTML Writers
Guild (IWA-HWG)

Alexander Graf, University of Innsbruck

Tina Holmboe, Greytower Technologies (Invited Expert)

John Kugelman, Progeny Systems

Luca Mascaro, International Webmasters Association / HTML Writers
Guild (IWA-HWG)

Shane McCarron, Applied Testing and Technology, Inc. (Invited Expert)

Michael Rawling, IVIS Group Limited

Gregory Rosmaita, Invited Expert

Sebastian Schnitzenbaumer, Dreamlab Technologies AG

Richard Schwerdtfeger, IBM

Elias Torres, IBM

Masataka Yakura, Mitsue-Links Co., Ltd.

Toshihiko Yamakami, ACCESS Co., Ltd.

The Best Equipment Deals | Best Music Deals
Midi Mime Types SiteMap Contact Subscribe © 2014 JimmyLandStudios