View source for RDFa

{{Short description|Format for expressing RDF statements in HTML documents}}
{{Infobox technology standard
| title             = RDF in Attributes
| status            = Published
| year_started      = 2004
| editors           = Ben Adida, Mark Birbeck
| base_standards    = [[Resource Description Framework|RDF]]
| related_standards = [[RDF Schema]], [[Web Ontology Language|OWL]]
| abbreviation      = RDFa
| domain            = [[Semantic Web]]
| website           = {{URL|http://www.w3.org/TR/rdfa-primer/}}
}}
'''RDFa''' or '''Resource Description Framework in Attributes'''<ref name="rdfa-primer"/> is a [[W3C]] Recommendation that adds a set of [[HTML attribute|attribute-level]] extensions to [[HTML5|HTML]], [[XHTML]] and various XML-based document types for embedding rich [[metadata]] within Web documents. The [[Resource Description Framework]] (RDF) data-model mapping enables its use for embedding RDF [[Resource Description Framework#Overview|subject-predicate-object expressions]] within XHTML documents. It also enables the extraction of RDF model triples by compliant [[user agent]]s.
The RDFa community runs a [[wiki]] website to host tools, examples, and tutorials.<ref name="rdfa wiki">{{cite web|url=http://rdfa.info/|title=RDFa / Tools}}</ref>
== History ==
RDFa was first proposed by [[Mark Birbeck]] in the form of a [[W3C]] note entitled ''XHTML and RDF'',<ref name="xhtml_and_rdf_note1" >{{cite web
|url=http://www.w3.org/MarkUp/2004/02/xhtml-rdf.html
|title=XHTML and RDF W3C Note 14 February 2004
|publisher=[[World Wide Web Consortium]]
|date=2004-02-14 |access-date=2007-12-27
}}</ref> which was then presented to the Semantic Web Interest Group<ref>{{cite web|url=http://www.w3.org/2001/sw/interest/|title=W3C Semantic Web Interest Group (SWIG)}}</ref> at the W3C's 2004 Technical Plenary.<ref name="xhtml_and_rdf_note2" >{{cite web
|url=http://www.xml.com/pub/a/2004/03/03/deviant.html
|title=Semantic Web Interest Group
|website=www.xml.com
|date=2004-03-03
|access-date=2007-12-27
}}</ref> Later that year the work became part of the sixth public Working Draft of XHTML 2.0.<ref name="xhtml_2_wd_6" >{{cite web
|url=http://www.w3.org/TR/2004/WD-xhtml2-20040722/mod-metaAttributes.html#s_metaAttributesmodule
|title=XHTML 2.0 W3C Working Draft 22 July 2004, 19. XHTML Metainformation Attributes Module
|publisher=[[World Wide Web Consortium]]
|date=2004-07-22
|access-date=2007-10-06
}}</ref><ref name="timelinehistory">{{cite web |url=http://www.dblab.ntua.gr/~bikakis/XML%20and%20Semantic%20Web%20W3C%20Standards%20Timeline-History.pdf |title=XML and Semantic Web W3C Standards Timeline |access-date=2013-06-28 |archive-date=2013-04-24 |archive-url=https://web.archive.org/web/20130424125723/http://www.dblab.ntua.gr/~bikakis/XML%20and%20Semantic%20Web%20W3C%20Standards%20Timeline-History.pdf |url-status=dead }}</ref>
Although it is generally assumed that RDFa was originally intended only for XHTML 2, in fact the purpose of RDFa was always to provide a way to add a metadata to ''any'' XML-based language. Indeed, one of the earliest documents bearing the ''RDF/A Syntax'' name has the sub-title ''A collection of attributes for layering RDF on XML languages''.<ref name="rdfa_1" >{{cite web
|url=http://www.w3.org/MarkUp/2004/rdf-a.html
|title=RDF/A Syntax: A collection of attributes for layering RDF on XML languages
|date=2004-10-11|access-date=2009-05-14
}}</ref> The document was written by Mark Birbeck and [[Steven Pemberton]], and was made available for discussion on October 11, 2004.
In April 2007 the XHTML 2 Working Group produced a module to support RDF annotation within the XHTML 1 family.<ref name="rdfa_modules_ed" >{{cite web
|url=http://www.w3.org/MarkUp/2007/ED-xhtml-rdfa-20070402
|title=XHTML RDFa Modules, Modules to support RDF annotation of elements, W3C Editor's Draft 2 April 2007
|publisher=[[World Wide Web Consortium]]
|date=2007-04-02
|access-date=2007-10-06
}}</ref>  As an example, it included an extended version of XHTML 1.1 dubbed [[XHTML+RDFa|XHTML+RDFa 1.0]]. Although described as not representing an intended direction in terms of a formal markup language from the W3C, limited use of the XHTML+RDFa 1.0 [[Document Type Definition|DTD]] did subsequently appear on the public Web.<ref name="xhtml_rdfa_1_examples">For examples of this, see: {{cite web |url=http://www.joost.com/09400ax |title=CBS: NCIS - Joost Link |access-date=2007-10-06 |url-status=dead |archive-url=https://web.archive.org/web/20071011062935/http://joost.com/09400ax |archive-date=2007-10-11 }} {{cite web |url=http://weborganics.co.uk/files/hAudio-RDFa.xhtml |title=WebOrganics :: HAudio RDFa |access-date=2007-10-06 |url-status=dead |archive-url=https://web.archive.org/web/20071214081908/http://weborganics.co.uk/files/hAudio-RDFa.xhtml |archive-date=2007-12-14 }}</ref>
October 2007 saw the first public Working Draft of a document entitled ''RDFa in XHTML: Syntax and Processing''.<ref name="rdfa_syntax_wd1" >{{cite web
|url=http://www.w3.org/TR/2007/WD-rdfa-syntax-20071018
|title= RDFa in XHTML: Syntax and Processing, A collection of attributes and processing rules for extending XHTML to support RDF, W3C Working Draft 18 October 2007|publisher=[[World Wide Web Consortium]]
|date=2007-10-18|access-date=2007-10-20
}}</ref>  This superseded and expanded upon the April draft; it contained rules for creating an RDFa parser, as well as guidelines for organizations wishing to make practical use of the technology.
In October 2008 RDFa 1.0 reached recommendation status.<ref name="rdfa_syntax_cr1" >{{cite web
|url=http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
|title= RDFa in XHTML: Syntax and Processing, A collection of attributes and processing rules for extending XHTML to support RDF, W3C Recommendation 14 October 2008
|publisher=[[World Wide Web Consortium]]
|date=2008-10-14 |access-date=2008-10-15
}}</ref>
RDFa 1.1 reached recommendation status in June 2012.<ref name="rdfa1_1_core_rec" >{{cite web
|url=http://www.w3.org/TR/2012/REC-rdfa-core-20120607
|title= RDFa Core 1.1 - Syntax and processing rules for embedding RDF through attributes
|publisher=[[World Wide Web Consortium]]
|date=2012-06-07 |access-date=2012-08-25
}}</ref> It differs from RDFa 1.0 in that it no longer relies on the XML-specific namespace mechanism. Therefore, it is possible to use RDFa 1.1 with non-XML document types such as HTML 4 or HTML 5. Details can be found in an appendix to HTML 5.<ref name="html_plus_rdfa1_1" >{{cite web
|url=http://www.w3.org/TR/2012/WD-rdfa-in-html-20120329
|title=HTML+RDFa 1.1 - Support for RDFa in HTML4 and HTML5
|publisher=[[World Wide Web Consortium]]
|date=2012-03-29 |access-date=2012-08-25
}}</ref>
An additional ''RDFa 1.1 Primer'' document was last updated 17 March 2015.<ref name="rdfa-primer"/> (The first public Working Draft dates back to 10 March 2006.<ref name="xhtml-rdfa-primer0">{{cite web
|url=https://www.w3.org/TR/2006/WD-xhtml-rdfa-primer-20060310/
|title=RDF/A Primer 1.0
|publisher=[[World Wide Web Consortium|W3C]]
|date=10 March 2006
|access-date=2016-09-02
}}</ref>)
==Versions and variants ==
There are some main well-defined variants of the basic concepts, that are used as reference and as abbreviation to the W3C standards.
=== HTML+RDFa ===
RDFa was defined in 2008 with the "RDFa in XHTML: Syntax and Processing" Recommendation.<ref name="RDFa2008">"RDFa in XHTML: Syntax and Processing - A collection of attributes and processing rules for extending XHTML to support RDF", W3C Recommendation 14 October 2008. http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/</ref> Its first application was to be a [[XHTML Modularization|module of XHTML]].
The HTML applications remained, ''"a collection of attributes and processing rules for extending XHTML to support RDF"'' expanded to HTML5, are now expressed in a specialized standard, the "HTML+RDFa" (the last is ''"HTML+RDFa 1.1 - Support for RDFa in HTML4 and HTML5"''<ref name="html-rdfa">"HTML+RDFa 1.1 - Support for RDFa in HTML4 and HTML5", W3C Recommendation 22 August 2013. http://www.w3.org/TR/html-rdfa/</ref>).
=== RDFa 1.0 ===
The ''"HTML+RDFa"'' syntax of 2008 was also termed ''"RDFa 1.0"'', so, there is no "RDFa Core 1.0" standard.
In general this 2008's ''RDFa 1.0'' is used with the old [[XHTML]] standards (as long as ''RDFa 1.1'' is used with XHTML5 and HTML5).
=== RDFa 1.1 ===
Is the first generic (for HTML and XML) RDFa standard; the "RDFa Core 1.1" is in the Third Edition, since 2015.<ref name="rdfa-core">"RDFa Core 1.1 - Third Edition - Syntax and processing rules for embedding RDF through attribute", W3C Recommendation 17 March 2015. https://www.w3.org/TR/2015/REC-rdfa-core-20150317/</ref>
===RDFa Lite ===
RDFa Lite is a W3C Recommendation (1.0 and 1.1) since 2009,<ref name=RDFaLite1.0>[http://www.w3.org/TR/2011/WD-rdfa-lite-20111208/ first draft 1.1].</ref> where it is described as follows:<ref name="RDFaLite1.1">"RDFa Lite 1.1, W3C Recommendation 07 June 2012. http://www.w3.org/TR/rdfa-lite/ ([http://www.w3.org/TR/2015/REC-rdfa-lite-20150210/ second edition at 2015])</ref>
<blockquote>
RDFa Lite is minimal subset of RDFa ... consisting of a few attributes that may be used to express [[machine-readable data]] in Web documents like HTML, SVG, and XML. While it is not a complete solution for advanced data markup tasks, it does work for most day-to-day needs and can be learned by most Web authors in a day.
</blockquote>
RDFa Lite consists of five attributes: vocab, typeof, property, resource, and prefix.<ref name=RDFaLite1.1/> RDFa 1.1 Lite is upwards compatible with RDFa 1.1.<ref name=RDFaLite1.1/>
In 2009 the W3C was positioned<ref>[http://www.w3.org/html/wg/tracker/issues/76 Final W3C position] (ISSUE-76), establishing that Microdata syntax simply duplicates what RDFa Lite already does.</ref> to retain ''RDFa Lite'' as unique and definitive standard alternative to [[Microdata (HTML)|Microdata]].<ref>{{cite web|url=http://manu.sporny.org/2012/mythical-differences|title=Mythical Differences: RDFa Lite vs. Microdata - The Beautiful, Tormented Machine}}</ref> The position was confirmed with the publication of the HTML5 Recommendation in 2014.
==Essence==
The essence of RDFa is to provide a set of attributes that can be used to carry metadata in an XML language (hence the 'a' in RDFa).
These attributes are:
; {{mono|about}} : a [[URI]] or [[CURIE]] specifying the resource the metadata is about
; {{mono|rel}} and {{mono|rev}} : specifying a relationship and reverse-relationship with another resource, respectively
; {{mono|src}}, {{mono|[[href]]}} and {{mono|resource}} : specifying the partner resource
; {{mono|property}} : specifying a property for the content of an element or the partner resource
; {{mono|content}} : optional attribute that overrides the content of the element when using the property attribute
; {{mono|datatype}} : optional attribute that specifies the [[datatype]] of text specified for use with the property attribute
; {{mono|typeof}} : optional attribute that specifies the RDF type(s) of the subject or the partner resource (the resource that the metadata is about).
==Benefits==
There are five "principles of interoperable metadata" met by RDFa.<ref>[http://assets.adida.net/presentations/w3c-2006-04-06/w3c-2006-04-06.pdf Building Interoperable Web Metadata]</ref>
* Publisher Independence – each site can use its own standards
* Data Reuse – data are not duplicated. Separate XML and HTML sections are not required for the same content.
* Self Containment – the HTML and the RDF are separated
* Schema Modularity – the attributes are reusable
Additionally RDFa may benefit [[web accessibility]] as more information is available to [[Assistive Technology Service Provider Interface|assistive technology]].<ref>{{cite web|url=http://www.standards-schmandards.com/2007/rdfa-and-accessibility/|title=RDFa – Implications for Accessibility – Standards Schmandards}}</ref>
==Usage ==
There is a growing number of tools for better usage of RDFa vocabularies and RDFa annotation.
=== HTML+RDFa statistics ===
[[File:RDFa-UsageStatistics-charts.png|thumb|280px|2013 survey pizza charts of percentage usage,<ref name="webstats2013"/> showing that 79% of URLs and 43% of domains use ''HTML+RDFa''. The average 61% (the other 39% was Microformats) is the ''usage indicator''.]]
Simplified approaches to semantically annotate information items in [[webpages]] were greatly encouraged by the [[#HTML+RDFa|HTML+RDFa]]  (released in 2008) and [[microformats]] (since ~2005) standards.
{{As of | 2013}} these standards were encoding events, contact information, products, and so on. Despite the [[vCard]] semantics (only basic items of [[person]] and [[organization]] annotations) dominance,<ref name="webstats2013">{{cite web |url=http://webdatacommons.org/structureddata/index.html#toc2
|date=2013 |work= section 3.1, "Extraction Results from the November 2013 Common Crawl Corpus" |access-date=2015-02-21 |title=Web Data Commons – RDFa, Microdata, and Microformat Data Sets}}</ref> and some [[boilerplate (text)|cloning]] of annotations along the same [[Domain name|domain]], the counting of webpages (URLs) and domains with annotations is an important statistical indicator for ''usage of semantically annotated information'' in the Web.
The statistics of 2017 show that usage<ref name="webstats2017">{{cite web|url=http://webdatacommons.org/structureddata/index.html#toc2
|date=2017 |work= section 3.1, "Extraction Results from the November 2017 Common Crawl Corpus" |access-date=2019-01-09 |title=Web Data Commons – RDFa, Microdata, and Microformat Data Sets}}</ref> of HTML+RDFa is now less than that of Microformats.
=== RDFa editors ===
;Web-based RDFa editors: There are already a few RDFa editors available online. [[RDFaCE]] (RDFa Content Editor) is a [[WYSIWYM]] editor based on [[TinyMCE]] to support RDFa content authoring. It supports manual and semi-automatic generation of RDFa with the support of annotation services such as [[DBpedia Spotlight]], [[OpenCalais]], [[Alchemy API]], among others.<ref>{{cite web|url=http://aksw.org/Projects/RDFaCE|title=RDFaCE — Agile Knowledge Engineering and Semantic Web (AKSW)}}</ref> RDFaCE-Lite is a version of RDFaCE also supporting [[Microdata (HTML)|Microdata]] and available as a WordPress plugin.<ref>{{cite web|url=http://aksw.org/Projects/RDFaCE|title=RDFaCE — Agile Knowledge Engineering and Semantic Web (AKSW)}}</ref>
;Desktop RDFa editors:  [[AutôMeta]] is an environment for semi-automatic (or automatic) annotation of documents for publishing on the Web using RDFa. It also includes a RDFa extraction tool to provide the user with a view of the annotated triples. It is available in both [[Command-line interface|CLI]] and [[GUI]] interfaces.<ref>{{cite web|url=http://code.google.com/p/autometa/|title=Google Code Archive - Long-term storage for Google Code Project Hosting.}}</ref>
===Examples===
The following is an example of adding [[Dublin Core]] metadata to an XML element in an XHTML file.  Dublin Core data elements are data typically added to a book or article (title, author, subject etc.)
<syntaxhighlight lang="xml">
<div xmlns:dc="http://purl.org/dc/elements/1.1/"
about="http://www.example.com/books/wikinomics">
<span property="dc:title">Wikinomics</span>
<span property="dc:creator">Don Tapscott</span>
<span property="dc:date">2006-10-01</span>
</div>
</syntaxhighlight>
Moreover, RDFa allows the passages and words within a text to be associated with semantic markup:
<syntaxhighlight lang="xml">
<div xmlns:dc="http://purl.org/dc/elements/1.1/"
about="http://www.example.com/books/wikinomics">
In his latest book
<span property="dc:title">Wikinomics</span>,
<span property="dc:creator">Don Tapscott</span>
explains deep changes in technology,
demographics and business.
The book is due to be published in
<span property="dc:date" content="2006-10-01">October 2006</span>.
</div>
</syntaxhighlight>
====XHTML + RDFa 1.0====
The following is an example of a complete XHTML+RDFa 1.0 document.  It uses [[Dublin Core]] and [[FOAF (software)|FOAF]], an ontology for describing people and their relationships with other people and things:
<syntaxhighlight lang="xml">
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:foaf="http://xmlns.com/foaf/0.1/"
xmlns:dc="http://purl.org/dc/elements/1.1/"
version="XHTML+RDFa 1.0" xml:lang="en">
<head>
<title>John's Home Page</title>
<base href="http://example.org/john-d/" />
<meta property="dc:creator" content="Jonathan Doe" />
<link rel="foaf:primaryTopic" href="http://example.org/john-d/#me" />
</head>
<body about="http://example.org/john-d/#me">
<h1>John's Home Page</h1>
<p>My name is <span property="foaf:nick">John D</span> and I like
<a href="http://www.neubauten.org/" rel="foaf:interest"
xml:lang="de">Einstürzende Neubauten</a>.
</p>
<p>
My <span rel="foaf:interest" resource="urn:ISBN:0752820907">favorite
book is the inspiring <span about="urn:ISBN:0752820907"><cite
property="dc:title">Weaving the Web</cite> by
<span property="dc:creator">Tim Berners-Lee</span></span></span>.
</p>
</body>
</html>
</syntaxhighlight>
In the example above, the document URI can be seen as representing an HTML document, but the document URI plus the "#me" string <code><nowiki>http://example.org/john-d/#me</nowiki></code> represents the actual person, as distinct from a document about them. The ''foaf:primaryTopic'' in the header tells us a URI of the person the document is about. The ''foaf:nick''  property (in the first <code>span</code> element) contains a nickname for this person, and the ''dc:creator'' property (in the <code>meta</code> element) tells us who created the document.  The hyperlink to the Einstürzende Neubauten website contains <code>rel="foaf:interest"</code>, suggesting that John Doe is interested in this band.  The URI of their website is a resource.
The ''foaf:interest'' inside the second <code>p</code> element is referring to a book by ISBN.  The <code>resource</code> attribute defines a resource in a similar way to the <code>href</code> attribute, but without defining a hyperlink.  Further into the paragraph, a <code>span</code> element containing an <code>about</code> attribute defines the book as another resource to specify metadata about.  The book title and author are defined within the contents of this tag using the ''dc:title'' and ''dc:creator'' properties.
Here are the same triples when the above document is automatically converted to [[RDF/XML]]:
<syntaxhighlight lang="xml">
<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<rdf:Description rdf:about="http://example.org/john-d/">
<dc:creator xml:lang="en">Jonathan Doe</dc:creator>
<foaf:primaryTopic>
<rdf:Description rdf:about="http://example.org/john-d/#me">
<foaf:nick xml:lang="en">John D</foaf:nick>
<foaf:interest rdf:resource="http://www.neubauten.org/"/>
<foaf:interest>
<rdf:Description rdf:about="urn:ISBN:0752820907">
<dc:creator xml:lang="en">Tim Berners-Lee</dc:creator>
<dc:title xml:lang="en">Weaving the Web</dc:title>
</rdf:Description>
</foaf:interest>
</rdf:Description>
</foaf:primaryTopic>
</rdf:Description>
</rdf:RDF>
</syntaxhighlight>
====HTML5 + RDFa 1.1 ====
The above example can be expressed without [[XML namespaces]] in [[HTML5]]:
<syntaxhighlight lang="html">
<html prefix="dc: http://purl.org/dc/elements/1.1/" lang="en">
<head>
<title>John's Home Page</title>
<link rel="profile" href="http://www.w3.org/1999/xhtml/vocab" />
<base href="http://example.org/john-d/" />
<meta property="dc:creator" content="Jonathan Doe" />
<link rel="foaf:primaryTopic" href="http://example.org/john-d/#me" />
</head>
<body about="http://example.org/john-d/#me">
<h1>John's Home Page</h1>
<p>My name is <span property="foaf:nick">John D</span> and I like
<a href="http://www.neubauten.org/" rel="foaf:interest"
lang="de">Einstürzende Neubauten</a>.
</p>
<p>
My <span rel="foaf:interest" resource="urn:ISBN:0752820907">favorite
book is the inspiring <span about="urn:ISBN:0752820907"><cite
property="dc:title">Weaving the Web</cite> by
<span property="dc:creator">Tim Berners-Lee</span></span></span>.
</p>
</body>
</html>
</syntaxhighlight>
Note how the prefix foaf is still used without declaration. RDFa 1.1 automatically includes prefixes for popular vocabularies such as FOAF.<ref name="rdfa_initial_context">{{cite web
|url=http://www.w3.org/2011/rdfa-context/rdfa-1.1
|title=RDFa Core Initial Context - Vocabulary Prefixes
|publisher=[[World Wide Web Consortium]]
|date=2012-05-27
|access-date=2012-08-25
}}</ref>
The minimal <ref>[http://www.w3.org/TR/html-rdfa/#document-conformance "Example of an HTML+RDFa 1.1 document" at www.w3.org]</ref> document is:
<syntaxhighlight lang="html"><html lang="en">
<head>
<title>Example Document</title>
</head>
<body vocab="http://schema.org/">
<p typeof="Blog">
Welcome to my <a property="url" href="http://example.org/">blog</a>.
</p>
</body>
</html></syntaxhighlight>
That is, it is recommended that all of these attributes are used: <code>vocab</code>, <code>typeof</code>, <code>property</code>; not only one of them.
'''RDFa Structured Data Example'''
Person Schema in RDFa.<ref>{{Cite web |last=Murari |first=Krishna |date=19 January 2023 |title=Person Schema in RDFa |url=https://www.theseotoday.com/2023/01/schema-markup-guide.html |url-status=live |archive-url=https://web.archive.org/web/20230119083602/https://www.theseotoday.com/2023/01/structured-data-guide.html |archive-date=19 January 2023 |access-date=19 January 2023 |website=The Seo Today}}</ref><syntaxhighlight lang="html" line="1">
<div vocab="http://schema.org/" typeof="Person">
<a property="image" href="http://manu.sporny.org/images/manu.png">
<span property="name">Manu Sporny</span></a>,
<span property="jobTitle">Founder/CEO</span>
<div>
Phone: <span property="telephone">(540) 961-4469</span>
</div>
<div>
E-mail: <a property="email" href="mailto:(your emailid)">msporny@digitalbazaar(.)com</a>
</div>
<div>
Links: <a property="url" href="http://manu.sporny.org/">Manu's homepage</a>
</div>
</div>
</syntaxhighlight>
==See also==
<!---♦♦♦ Please keep the list in alphabetical order ♦♦♦--->
* [[Embedded RDF|eRDF]], an alternative to RDFa (now obsolete)
* [[GRDDL]], a way to extract (annotated) data out of XHTML and [[XML]] documents and transform it into an RDF graph
* [[Microdata (HTML)|Microdata]] - another approach at embedding semantics in HTML using additional attributes
* [[Microformat]]s, a simplified approach to semantically annotate data in web pages
* [[Open Graph protocol]], a way to use RDFa to integrate web pages into the Facebook social graph
* [[Schema.org]], search-engine supported schemas for structured data markup on web pages that can be expressed as RDFa
==References==
{{reflist|30em|refs=
<ref name="rdfa-primer">{{cite web
|url=https://www.w3.org/TR/2015/NOTE-rdfa-primer-20150317/
|title=RDFa 1.1 Primer
|edition=3rd
|publisher=[[World Wide Web Consortium|W3C]]
|date=17 March 2015
|access-date=2016-09-02
}}</ref>
}}
==External links==
* [http://www.w3.org/TR/rdfa-primer/ RDFa Primer]
* [http://www.w3.org/2006/07/SWD/wiki/hGRDDL_Example hGRDDL]
* [http://www.standards-schmandards.com/2007/rdfa-and-accessibility/ RDFa – Implications for Accessibility]
* [https://www.youtube.com/watch?v=mxE3FeOyS-E Mark Birbeck presenting RDFa at Google in May 2008]. Video archived at [https://ghostarchive.org/varchive/mxE3FeOyS-E ghostarchive.org] on 24 May 2022.
{{Semantic Web}}
{{DEFAULTSORT:Rdfa}}
[[Category:Resource Description Framework]]
[[Category:Metadata publishing]]
[[Category:Semantic Web]]
[[Category:Semantic HTML]]
[[Category:XML-based standards]]
[[Category:World Wide Web Consortium standards]]
[[Category:Domain-specific knowledge representation languages]]
[[Category:WordPress]]