RDFa in XHTML: Syntax and Processing

http://www.w3.org/TR/rdfa-syntax Archived on 2026-04-24 10:04 UTC

RDFa in XHTML: Syntax and Processing
RDFa in XHTML: Syntax and Processing
A collection of attributes and processing rules for extending XHTML to support RDF
W3C Recommendation 14 October 2008
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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
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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
).
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:
cc:
dbp:
dbr:
dc:
ex:
foaf:
rdf:
rdfs:
taxo:
xhv:
xsd:
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
CURIE
s, used for expressing relationships between two resources ('predicates' in RDF terminology);
@rev
a whitespace separated list of
CURIE
s, 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
URI
for expressing the partner resource of a relationship (a 'resource object', in
RDF terminology);
@src
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
URIorSafeCURIE
, used for stating what the data is about (a 'subject' in RDF terminology);
@property
a whitespace separated list of
CURIE
s, used for expressing relationships between a subject and some literal text (also a 'predicate');
@resource
URIorSafeCURIE
for expressing the partner resource of a relationship that is not intended to be 'clickable' (also an
'object');
@datatype
CURIE
representing a datatype, to express the datatype of a literal;
@typeof
a whitespace separated list of
CURIE
s 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:

Page 7

...

RDFa makes use of this concept, enhancing it with the ability to make use of other vocabularies by using compact URIs:
xmlns="http://www.w3.org/1999/xhtml"
xmlns:foaf="http://xmlns.com/foaf/0.1/"
xmlns:dc="http://purl.org/dc/elements/1.1/"

My home-page

...

Although not widely used, XHTML already supports the use of
@rel
and
@rev
on the
element. This becomes more useful in RDFa with
the addition of support for different vocabularies:
This document is licensed under a
xmlns:cc="http://creativecommons.org/ns#"
rel="cc:license"
href="http://creativecommons.org/licenses/by-nc-nd/3.0/">
Creative Commons License
.
Not only can URLs in the document be re-used to provide metadata, but so can inline text:
xmlns="http://www.w3.org/1999/xhtml"
xmlns:cal="http://www.w3.org/2002/12/cal/ical#"
Jo's Friends and Family Blog

I'm holding
property="cal:summary"
one last summer Barbecue
,
on September 16th at 4pm.

If some displayed text is different to the actual 'value' it represents, more precise values can be added, which can optionally include datatypes:
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"
Jo's Friends and Family Blog

I'm holding

one last summer Barbecue
,
on
property="cal:dtstart"
content="2007-09-16T16:00:00-05:00"
datatype="xsd:dateTime"
September 16th at 4pm
.

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:
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"
Jo's Friends and Family Blog

typeof="cal:Vevent"
I'm holding

one last summer Barbecue
,
on
datatype="xsd:dateTime">
September 16th at 4pm
.

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:
xmlns="http://www.w3.org/1999/xhtml"
xmlns:biblio="http://example.org/"
xmlns:dc="http://purl.org/dc/elements/1.1/"

Books by Marco Pierre White

I think White's book
'about="urn:ISBN:0091808189"
typeof="biblio:book"
property="dc:title"
Canteen Cuisine
'
is well worth getting since although it's quite advanced stuff, he
makes it pretty easy to follow. You might also like
about="urn:ISBN:1596913614"
typeof="biblio:book"
property="dc:description"
White's autobiography
.

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
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 [
] URI for Albert Einstein, instead of the ambiguous string 'Albert':

has the name
Albert Einstein.

was born on
March 14, 1879.

was born in
Germany.

has a picture at
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:

has the name
Albert Einstein

was born on
March 14, 1879

was born in

has a picture at
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:

"Albert Einstein".

"March 14, 1879".

.

.
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:

"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

"1879-03-14"
^^
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: .
@prefix foaf: .

foaf:name
"Albert Einstein" .

dbp:birthPlace
.
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: .
@prefix dbr: .
@prefix foaf: .
@prefix xsd: .
dbr:Albert_Einstein
dbp:dateOfBirth "1879-03-14"^^
xsd:date
dbr:Albert_Einstein
foaf:depiction .
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
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
Sample root element

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

html
xmlns="http://www.w3.org/1999/xhtml"
version="XHTML+RDFa 1.0"
xml:lang="en">

Virtual Library

Moved to example.org.

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:

Albert Einstein
1879-03-14

resource="http://dbpedia.org/resource/Germany"
Federal Republic of Germany

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:

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:

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:

dbp:citizenship .

dbp:citizenship .
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:

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

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:
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:
xmlns:db="http://dbpedia.org/"
...

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

...

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:
xmlns:dbr="http://dbpedia.org/resource/"

...

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:
xmlns:dbr="http://dbpedia.org/resource/"

...

xmlns:dbr="http://someotherdb.org/resource/"

...

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:
about="http://dbpedia.org/resource/Albert_Einstein"
...

whilst to express a CURIE they would do this:
about="[dbr:Albert_Einstein]"
...

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.
about="[Albert_Einstein]"
...

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

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:

would generate this triple:
<> .
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:

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:
href="mailto:john@example.org" />
href="mailto:sue@example.org" />
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 .
_:sue foaf:mbox .
_: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
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:

Jo's Friends and Family Blog

...

This would generate the following triples:
<> foaf:primaryTopic <#bbq> .
<> dc:creator "Jo" .
It is possible for the data to appear elsewhere in the document:

Jo's Blog

Jo
's blog

Welcome to my blog.

which would still generate the triple:
<> dc:creator "Jo" .
The value of
base
may change the initial value of [
current subject
]:

Jo's Friends and Family Blog

...

A parser should now generate the following triples, regardless of the URL from which the XHTML document is served:
foaf:primaryTopic <#bbq> .
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:

Jo's Friends and Family Blog

about="#bbq"
typeof="cal:Vevent"
I'm holding
property="cal:summary"
one last summer barbecue
,
on
property="cal:dtstart"
content="2007-09-16T16:00:00-05:00"
datatype="xsd:dateTime">
September 16th at 4pm
.

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

Sue knows
about="mailto:sue@example.org"
rel="foaf:knows" href="mailto:jim@example.org">Jim.
This should generate the following triples:
foaf:knows .
foaf:knows .
Similarly, authors may make statements about images:
about="photo1.jpg"
this photo was taken by
Mark Birbeck

which should generate the following triples:
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:
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:
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:

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

The complete mark-up yields three triples:
foaf:img .
xhv:license .
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:
typeof="foaf:Person"
Albert Einstein
Albert

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:

Albert Einstein
1879-03-14

property="dbp:conventionalLongName">Federal Republic of Germany

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

Albert Einstein
1879-03-14

property="dbp:conventionalLongName">Federal Republic of Germany

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

Albert Einstein
1879-03-14

resource="http://dbpedia.org/resource/Germany"
Federal Republic of Germany

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:

Albert Einstein
1879-03-14

Federal Republic of Germany

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:
foaf:name "Albert Einstein" .
dbp:dateOfBirth "1879-03-14"^^xsd:date .
dbp:birthPlace .
whilst the second group refer to the
@resource
that contains them:

dbp:conventionalLongName "Federal Republic of Germany" .

dbp:capital .
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:

Albert Einstein
1879-03-14

A parser should generate the following triples:

dbp:influenced .
foaf:name "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

Albert Einstein
1879-03-14

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:
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:

Albert Einstein
1879-03-14

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

rel="dbp:influenced"
Albert Einstein
1879-03-14

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:

Albert Einstein
1879-03-14

and then a further statement that the 'long name' for Germany is the
Federal Republic of Germany
property="dbp:conventionalLongName">Federal Republic of Germany
RDFa allows authors to insert this statement as a self-contained unit into other contexts:

Albert Einstein
1879-03-14

property="dbp:conventionalLongName">Federal Republic of Germany

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

Albert Einstein
1879-03-14

property="dbp:conventionalLongName">Federal Republic of Germany

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:
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':
dbp:birthPlace

and second it is used to generate its own triple:
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:

In this example there is one incomplete triple:
dbp:citizenship
When the processor meets each of the
@about
values, this triple is completed, giving:

dbp:citizenship

dbp:citizenship

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:

typeof="foaf:Person"
Albert Einstein
1879-03-14

typeof="foaf:Person"
Arthur Schopenhauer
1788-02-22

First the following incomplete triple is stored:
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:
dbp:influenced
_:a
_:a
rdf:type foaf:Person .
_:a
foaf:name "Albert Einstein" .
_:a
dbp:dateOfBirth "1879-03-14"^^xsd:date .
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:

Albert Einstein
1879-03-14

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:
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:
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

_:a dbp:citizenship

The entire set of triples that a parser should generate are as follows:
dbp:influenced
_:a
_:a
foaf:name "Alber Einstein" .
_:a
dbp:dateOfBirth "1879-03-14"^^xsd:date .
_:a
dbp:citizenship .
_:a
dbp:citizenship .
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:
property="dc:creator"
content="Mark Birbeck"
/>
The [
plain literal
] can also be specified by using the content of the element:
property="dc:creator">
Mark Birbeck

Both of these examples give the following triple:
dc:creator "Mark Birbeck" .
The value of
@content
is given precedence over any element content, so the following would give exactly the same triple:
property="dc:creator"
content="Mark Birbeck"
>John Doe
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]

"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:
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:
xmlns:ex="http://www.example.com/ns/"
xml:lang="fr"

Example
property="ex:property" content="chat" />

...

6.3.1.2. Typed literals
Literals can be given a data type using
@datatype
This can be represented in RDFa as follows:
datatype="xsd:dateTime"
September 16th at 4pm
.
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):

content="E = mc²: The Most Urgent Problem of Our Time"
/>

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
<sup>2</sup>
: The Most Urgent Problem of Our Time" .
RDFa therefore supports the use of normal mark-up to express XML literals, by using
@datatype

E = mc²: The Most Urgent Problem of Our Time

This would generate the following triple, with the XML preserved in the literal:
<> dc:title "E = mc²: 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

E = mc²: The Most Urgent Problem of Our Time

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:

You searched for Einstein:

datatype=""
>Albert Einstein
(b. March 14, 1879, d. April 18, 1955) was a German-born theoretical physicist.

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:
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:
property="dc:title"
Example 3: ...

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:

On Crime and Punishment

resource="urn:ISBN:0140449132"

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!

The
blockquote
element generates the following triple:

.
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:
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:

rel="dc:creator" rev="foaf:img"
href="http://www.blogger.com/profile/1109404" />
which then yields two triples:

dc:creator .

foaf:img .
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
. 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,
);
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
, 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
CURIE
s.
URIorSafeCURIE
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.
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
rel="cite"
resource="http://www.example.com/books/the_two_towers">
The Two Towers
,
"The hospitality of
your hall is somewhat lessened of late, Theoden King."
which would generate the following triples:
<> xhv:cite .
cite
is also useful for referencing specifications:
cite to reference another specification
More information can be found in
rel="cite"
resource="http://www.w3.org/TR/REC-xml">[XML].
which would generate the following triples:
<> xhv:cite .
chapter
Refers to a resource serving as a chapter in a collection.
contents
Refers to a resource serving as a table of contents.
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
. The latest version
is available at

% XHTML.global.attrs.prefixed
"IGNORE" >

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

% about.attrib
"about %URIorSafeCURIE.datatype; #IMPLIED"

% XHTML.global.about.attrib
"%XHTML.prefix;:about %URIorSafeCURIE.datatype; #IMPLIED"
]]>

% typeof.attrib
"typeof %CURIEs.datatype; #IMPLIED"

% XHTML.global.typeof.attrib
"%XHTML.prefix;:typeof %CURIEs.datatype; #IMPLIED"
]]>

% property.attrib
"property %CURIEs.datatype; #IMPLIED"

% XHTML.global.property.attrib
"%XHTML.prefix;:property %CURIEs.datatype; #IMPLIED"
]]>

% resource.attrib
"resource %URIorSafeCURIE.datatype; #IMPLIED"

% XHTML.global.resource.attrib
"%XHTML.prefix;:resource %URIorSafeCURIE.datatype; #IMPLIED"
]]>

% content.attrib
"content CDATA #IMPLIED"

% XHTML.global.content.attrib
"%XHTML.prefix;:content CDATA #IMPLIED"
]]>

% datatype.attrib
"datatype %CURIE.datatype; #IMPLIED"

% XHTML.global.datatype.attrib
"%XHTML.prefix;:datatype %CURIE.datatype; #IMPLIED"
]]>

% rel.attrib
"rel %CURIEs.datatype; #IMPLIED"

% XHTML.global.rel.attrib
"%XHTML.prefix;:rel %CURIEs.datatype; #IMPLIED"
]]>

% rev.attrib
"rev %CURIEs.datatype; #IMPLIED"

% XHTML.global.rev.attrib
"%XHTML.prefix;:rev %CURIEs.datatype; #IMPLIED"
]]>

% Metainformation.extra.attrib
"" >

% Metainformation.attrib
"%about.attrib;
%content.attrib;
%datatype.attrib;
%typeof.attrib;
%property.attrib;
%rel.attrib;
%resource.attrib;
%rev.attrib;
%Metainformation.extra.attrib;"

% XHTML.global.metainformation.extra.attrib
"" >

% 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;"
]]>

% XHTML.global.metainformation.attrib
"" >

A.2. XHTML+RDFa Content Model Module
You can download this version of this file from
. The latest version is
available at

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

% Edit.class
"| %ins.qname; | %del.qname;" >

% Script.class
"| %script.qname; | %noscript.qname;" >

% Misc.extra
"" >

% Misc.class
"%Edit.class;
%Script.class;
%Misc.extra;"

% InlStruct.class
"%br.qname; | %span.qname;" >

% I18n.class
"| %bdo.qname;" >

% Anchor.class
"| %a.qname;" >

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

% Inline.extra
"" >

% Ruby.class
"| %ruby.qname;" >

% Inline.class
"%InlStruct.class;
%InlPhras.class;
%InlPres.class;
%I18n.class;
%Anchor.class;
%InlSpecial.class;
%InlForm.class;
%Ruby.class;
%Inline.extra;"

% InlNoRuby.class
"%InlStruct.class;
%InlPhras.class;
%InlPres.class;
%I18n.class;
%Anchor.class;
%InlSpecial.class;
%InlForm.class;
%Inline.extra;"

% NoRuby.content
"( #PCDATA
| %InlNoRuby.class;
%Misc.class; )*"

% InlNoAnchor.class
"%InlStruct.class;
%InlPhras.class;
%InlPres.class;
%I18n.class;
%InlSpecial.class;
%InlForm.class;
%Ruby.class;
%Inline.extra;"

% InlNoAnchor.mix
"%InlNoAnchor.class;
%Misc.class;"

% Inline.mix
"%Inline.class;
%Misc.class;"

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

% Table.class
"| %table.qname;" >

% Form.class
"| %form.qname;" >

% Fieldset.class
"| %fieldset.qname;" >

% BlkStruct.class
"%p.qname; | %div.qname;" >

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

% BlkPres.class
"| %hr.qname; " >

% BlkSpecial.class
"%Table.class;
%Form.class;
%Fieldset.class;"

% Block.extra
"" >

% Block.class
"%BlkStruct.class;
%BlkPhras.class;
%BlkPres.class;
%BlkSpecial.class;
%Block.extra;"

% Block.mix
"%Heading.class;
| %List.class;
| %Block.class;
%Misc.class;"

% Flow.mix
"%Heading.class;
| %List.class;
| %Block.class;
| %Inline.class;
%Misc.class;"

A.3. XHTML+RDFa Driver Module
You can download this version of this file from
. The latest version is available at

% XHTML.version
"XHTML+RDFa 1.0" >

% NS.prefixed
"IGNORE" >
% XHTML.prefix
"xhtml" >

% XHTML.global.attrs.prefixed
"INCLUDE" >

% XLINK.xmlns
"" >
% XLINK.xmlns.attrib
"" >

% XHTML.profile
"" >

% xhtml-notations.module
"IGNORE" >

% XHTML.bidi
"INCLUDE" >

% xhtml-prefw-redecl.module
"IGNORE" >
% xhtml-prefw-redecl.mod
"" >
%xhtml-prefw-redecl.mod;
]]>

% xhtml-datatypes.module
"INCLUDE" >
% xhtml-datatypes.mod
PUBLIC "-//W3C//ENTITIES XHTML Datatypes 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-datatypes-1.mod" >
%xhtml-datatypes.mod;]]>

% xhtml-metaAttributes.module
"INCLUDE" >
% xhtml-metaAttributes.mod
PUBLIC "-//W3C//ENTITIES XHTML MetaAttributes 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-metaAttributes-1.mod" >
%xhtml-metaAttributes.mod;]]>

% xhtml-events.module
"INCLUDE" >

% Common.extra.attrib
"href %URI.datatype; #IMPLIED
%Metainformation.attrib;"

% xhtml-inlstyle.module
"INCLUDE" >
% 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;]]>

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

% xhtml-framework.module
"INCLUDE" >
% 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;]]>

% xhtml-postfw-redecl.module
"IGNORE" >
% xhtml-postfw-redecl.mod
"">
%xhtml-postfw-redecl.mod;
]]>

% xhtml-text.module
"INCLUDE" >
% xhtml-text.mod
PUBLIC "-//W3C//ELEMENTS XHTML Text 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-text-1.mod" >
%xhtml-text.mod;]]>

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

% xhtml-list.module
"INCLUDE" >
% xhtml-list.mod
PUBLIC "-//W3C//ELEMENTS XHTML Lists 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-list-1.mod" >
%xhtml-list.mod;]]>

% xhtml-edit.module
"INCLUDE" >
% 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;]]>

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

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

% link.attlist
"IGNORE" >

% xhtml-link.module
"INCLUDE" >
% 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;]]>

%Common.attrib;
charset %Charset.datatype; #IMPLIED
hreflang %LanguageCode.datatype; #IMPLIED
type %ContentType.datatype; #IMPLIED
media %MediaDesc.datatype; #IMPLIED

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

% xhtml-base.module
"INCLUDE" >
% 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;]]>

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

%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.attlist
"IGNORE" >
% xhtml-style.module
"INCLUDE" >
% 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;]]>
%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

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

% area.attlist
"IGNORE" >

% xhtml-csismap.module
"INCLUDE" >
% 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;]]>

%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

% xhtml-ssismap.module
"INCLUDE" >
% 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.attlist
"IGNORE" >
% xhtml-param.module
"INCLUDE" >
% 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;]]>

%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

% xhtml-object.module
"INCLUDE" >
% 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;]]>

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

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

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

% xhtml-legacy.module
"IGNORE" >
% 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;]]>

% html.attlist
"IGNORE" >
% head.attlist
"IGNORE" >
% title.attlist
"IGNORE" >
% xhtml-struct.module
"INCLUDE" >
% 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;]]>
% profile.attrib
"profile %URI.datatype; '%XHTML.profile;'"
% XHTML.version.attrib
"version %FPI.datatype; #FIXED '%XHTML.version;'"
%Common.attrib;
%XSI.schemaLocation.attrib;
%XHTML.version.attrib;
%Common.attrib;
%profile.attrib;
%Common.attrib;

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
. The latest version is available at
-- .......................................................................... --
-- File catalog ............................................................ --

-- XHTML+RDFa Catalog Data File

Revision: $Revision: 1.3 $

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:

-- .......................................................................... --
-- 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
). 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:

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"

B.2. XML DTD Definition
The following
informative
XML DTD definition for these datatypes is included as an example:

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:
"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
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:
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
.)
DC
Dublin Core Metadata Initiative (DCMI) (See
.)
FOAF-PROJECT
The FOAF Project (See
.)
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
.)
RDFa Primer
RDFa Primer 1.0 - Embedding Structured Data in Web Pages (see
.)
RDF-CONCEPTS
Resource Description Framework (RDF): Concepts and Abstract Syntax (See
.)
RDF-PRIMER
RDF Primer (See
.)
RDF-SYNTAX
RDF/XML Syntax and Grammar (See
.)
RDFTESTS-DATATYPES-TEST001
datatypes/test001.nt (See
.)
RDFTESTS-RDFMS-XMLLANG-TEST006
rdfms-xmllang/test006.nt (See
.)
RELAXNG
RELAX NG Home Page (See
.)
SWD-WG
Semantic Web Deployment Working Group (See
.)
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:
XHTML2-WG
XHTML 2 Working Group (See
.)
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.

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