XHTML+RDFa

{{Short description|Extended version of the XHTML for supporting RDF}}

{{Infobox file format

| name = XHTML+RDFa

| icon =

| logo =

| caption =

| extension = .xhtml, .xht,
.xml, .html, .htm

| mime = application/xhtml+xml

| type code =

| uniform type =

| magic =

| owner = World Wide Web Consortium

| released = {{Start date|2008|10|14|df=yes}}

| latest release version = 1.1

| latest release date = {{Start date and age|2010|08|03|df=yes}}

| creatorcode =

| genre = Host language

| screenshot =

| container for =

| contained by =

| extended from = XML, HTML

| extended to =

| standard = [https://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/ 1.0 (Recommendation)],

[https://www.w3.org/TR/2015/REC-xhtml-rdfa-20150317/ 1.1 (Recommendation)]

| free =

| url =

}}

XHTML+RDFa (Extensible Hypertext Markup Language + Resource Description Framework in attributes) is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. XHTML+RDFa is one of the techniques used to develop Semantic Web content by embedding rich semantic markup.

Version 1.1 of the language is a superset of XHTML 1.1, integrating the attributes according to RDFa Core 1.1. In other words, it is an RDFa support through XHTML Modularization.

RDFa in XHTML version 1.0 became a World Wide Web Consortium (W3C) Recommendation on 14 October 2008.{{cite web |url=https://www.w3.org/TR/2008/REC-rdfa-syntax-20081014/ |title=RDFa in XHTML: Syntax and Processing. W3C Recommendation 14 October 2008.}}{{cite journal|url=https://www.academia.edu/2986178 |title=XML and Semantic Web W3C Standards Timeline|journal=Semantic Hyper/Multi-Media Adaptation: Schemes and Applications, Springer 2013 |last1=Bikakis |first1=Nikos }}

The current recommendation is RDFa+XHTML version 1.1, which became a W3C Recommendation on 7 June 2012{{cite web |url=https://www.w3.org/TR/2012/REC-xhtml-rdfa-20120607/ |title=XHTML+RDFa 1.1. Support for RDFa via XHTML Modularization. W3C Recommendation 07 June 2012.}} and was updated with a ”Second Edition” on 22 August 2013{{cite web |url=https://www.w3.org/TR/2013/REC-xhtml-rdfa-20130822/ |title=XHTML+RDFa 1.1 - Second Edition. Support for RDFa via XHTML Modularization. W3C Recommendation 22 August 2013.}} and a ”Third Edition” on 17 March 2015.{{cite web |url=https://www.w3.org/TR/2015/REC-xhtml-rdfa-20150317/ |title=XHTML+RDFa 1.1 - Third Edition. Support for RDFa via XHTML Modularization. W3C Recommendation 17 March 2015.}}

Version 1.1 is based on [http://www.w3.org/TR/2013/REC-xhtml-rdfa-20130822/#xhtml-rdfa-1.1-definition XHTML™ 1.1 - Module-based XHTML - Second Edition]. Version 1.0 was based on the first edition.

Overview

Conventional Web documents contain large amounts of structured data that can be rendered in web browsers. This approach works fine for publishing purposes, however, a large amount of data stored in Web documents cannot be processed this way. XHTML+RDFa can provide machine-readable metadata within the markup code which makes additional user functionalities available. Most important of all, actions can be performed automatically that enables up-to-date publishing, structured search and sharing.{{cite book | title = Semantic Web for Dummies | author = Jeffrey T. Pollock | publisher = Wisley Publishing, Inc. | year = 2009 | isbn = 978-0-470-39679-7 | page = [https://archive.org/details/isbn_9780470396797/page/172 172] | url = https://archive.org/details/isbn_9780470396797/page/172 }}

RDFa can serve as a bridge between the "human and data webs".{{cite book | title = Designing with Web standards | url = https://archive.org/details/designingwithweb00zeld_395 | url-access = limited |author1=Jeffrey Zeldman |author2=Ethan Marcotte | publisher = New Riders | edition = third | year = 2009 | isbn = 978-0-321-61695-1 | page = [https://archive.org/details/designingwithweb00zeld_395/page/n96 76] }}

The potential in web documents enriched with RDFa is increasing since major search engines begin to process them while indexing. Yahoo indexes RDFa and microformats since 2008 and Google since 2009.{{cite web | url = http://www.alistapart.com/articles/introduction-to-rdfa |title = Introduction to RDFa | author = Mark Birbeck | year = 2009 | access-date=2010-09-07 }}

The RDFa attribute specifications make it possible to describe structured data in any markup language. The RDFa markup in XHTML+RDFa reuses the markup code, thus eliminating the need for unnecessary duplications.

XHTML+RDFa is not widely distributed yet, probably due to the lack of support in authoring tools and content management systems.{{cite book | title = Scripting Intelligence: Web 3.0 Information, Gathering and Processing | author = Mark Watson | publisher = Apress, Inc. | year = 2009 | isbn = 978-1-4302-2351-1 | page = [https://archive.org/details/scriptingintelli00wats/page/347 347] | url = https://archive.org/details/scriptingintelli00wats/page/347 }} However, there is good tendency. Drupal 7, for example, supports RDFa.{{cite web | url = http://www.w3.org/2010/Talks/RDFa-Drupal-Tutorial/ | title = Combine the Web of Data and the Web of Documents (RDFa and Drupal 7) |author1=Ivan Herman |author2=Stéphane Corlosquet |author3=Lin Clark | year = 2010 | access-date=2010-09-07 }}

Since the “a” in RDFa stands for attributes, it is straightforward to use CSS selectors to style the code.{{cite book | title = AdvancED CSS |author1=Joseph R. Lewis |author2=Meitar Moscovitz | publisher = Friendsof | year = 2009 | isbn = 978-1-4302-1932-3 | page = 224 }}

Document Type Definition

The combination of XHTML 1.1 and RDFa modules is claimed to be an example markup language. The Document Type Definition (DTD) is published at the W3C website.{{cite web | url = http://www.w3.org/TR/2013/REC-xhtml-rdfa-20130822/#deployment-advice | title = XHTML 1.1 + RDFa DTD | publisher = World Wide Web Consortium }}

According to the document type declaration, the identifiers of an XHTML+RDFa document should look like the following:

"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-2.dtd">

An example XHTML+RDFa document:

"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-2.dtd">

XHTML+RDFa document example

...

Authoring

The RDFa metadata is embedded as an XHTML attribute of the document element, generally the XHTML tag. The annotation syntax provided by RDFa can be used to express RDF statements in XHTML documents.{{cite book | title = Proceedings of ICWE 2010, Web Engineering: 10th International Conference | url = https://archive.org/details/webengineeringth00bena | url-access = limited |editor1=Boualem Benatallah |editor2=Fabio Casati |editor3=Gerti Kappel | publisher = Springer | year = 2010 | isbn = 978-3-642-13910-9 | page = [https://archive.org/details/webengineeringth00bena/page/n267 255] }}

Validation

XHTML+RDFa documents can be validated individually online at the W3C Markup Validation Service or together with CSS and RSS at W3C Unicorn. The validity of XHTML+RDFa documents can be indicated by the XHTML+RDFa conformance icons of W3C .