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Daniel K. Schneider: /* RDF basics */

2013-03-15T16:03:41Z

RDF basics

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== Definition ==

* The Resource Description Framework (RDF) is a language for representing information about resources in the World Wide Web.

* Originally RDF was primarily intended to represent metadata about Web resources, such as the title, author, and modification date of a Web page, copyright and licensing information about a Web document, or the availability schedule for some shared resource. However, by generalizing the concept of a "Web resource", RDF can also be used to '''represent information about things that can be identified on the Web''', i.e. the [[semantic web]].

== Major RDF vocabularies ==

; Metadata

* [[Learning Object Metadata Standard]]
* [[Dublin Core]]

; Content syndication and social software

* [[RSS]] 1.0 which is not very popular, most RSS formats are ''not'' RDF since bloggers don't understand issues related to the semantic web :)
* [[FOAF]] Friends-of-a-friend vocabulary for person networks

; Semantic Web
* [[OWL]]
* [[SKOS]] (Simple Knowledge Organisation System)
* [[SPARQL]] (Query language)

== RDF basics ==

At its core, RDF has a simple relational data model: Subject - Verb - Object ''or expressed differently'' Predicate (Subject, Object)
* Subject = The resource
* Object = Value
* Verb = Predicate = propriety = relation of the subjet with the object

Here is a typical RDF fragment

<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:mon_schema="http://tecfa.unige.ch/lib/mon_schema" >
<rdf:Description rdf:about="http://tecfa.unige.ch/perso/staf/lattion/">
<mon_schema:Creator>Stéphane Lattion</mon_schema:Creator>
</rdf:Description>
</rdf:RDF>

It expresses a relation like this:
[[image:rdf-simple-relation.png|frame|none|A simple ressource-author relationship]]

== RDF and the semantic web ==

=== The RDF Software stack ===

[[image:rdf-software-stack.png|frame|none|The RDF software stack]]

=== The RDF bus ===

[[image:rdf-bus-clients.png|frame|none|Software clients of the RDF bus]]

== Turtle syntax ==

Since XML/RDF code is some verbose, writing it manually is fairly time consuming. The W3C team proposes a "textual syntax for RDF called Turtle that allows RDF graphs to be completely written in a compact and natural text form, with abbreviations for common usage patterns and datatypes" ([http://www.w3.org/TeamSubmission/turtle/ Turtle - Terse RDF Triple Language], retrieved 15:31, 10 March 2008 (MET)).

Example:
<pre>
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:ex="http://example.org/stuff/1.0/">
<rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar"
dc:title="RDF/XML Syntax Specification (Revised)">
<ex:editor>
<rdf:Description ex:fullName="Dave Beckett">
<ex:homePage rdf:resource="http://purl.org/net/dajobe/" />
</rdf:Description>
</ex:editor>
</rdf:Description>
</rdf:RDF>
</pre>
becomes in turtle syntax:
<pre>
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix ex: <http://example.org/stuff/1.0/> .

<http://www.w3.org/TR/rdf-syntax-grammar>
dc:title "RDF/XML Syntax Specification (Revised)" ;
ex:editor [
ex:fullname "Dave Beckett";
ex:homePage <http://purl.org/net/dajobe/>
] .
</pre>

== Links ==

=== Standards ===

* [http://www.w3.org/RDF/Overview.html Resource Description Framework (RDF) Overview]
* [http://www.w3.org/TR/rdf-concepts/ Resource Description Framework (RDF): Concepts and Abstract Syntax], W3C Recommendation 10 February 2004
* [http://www.w3.org/TR/WD-rdf-syntax/ Resource Description Framework (RDF) Model and Syntax].
* [http://www.w3.org/TR/rdf-mt/ RDF Semantics], W3C Recommendation 10 February 2004 (rather difficult reading).
* [http://www.w3.org/TR/rdf-syntax-grammar/ RDF/XML Syntax Specification], W3C Recommendation 10 February 2004.
* [http://www.w3.org/TR/rdf-schema/ RDF Vocabulary Description Language 1.0: RDF Schema], W3C Recommendation 10 February 2004
* [http://www.w3.org/TeamSubmission/turtle/ Turtle - Terse RDF Triple Language]

; RDF Namespaces
* [http://ebiquity.umbc.edu/blogger/100-most-common-rdf-namespaces/ 100 most common RDF namespaces]

;RDF and XHTML
* See the [[RDFa]] article
* [http://www.w3.org/TR/xhtml-rdfa-primer/ RDFa Primer 1.0 Embedding RDF in XHTML] (Working Draft in March 2007)

; OWL
* [http://www.w3.org/TR/owl-features/ OWL Web Ontology Language Overview], W3C Recommendation 10 February 2004.
* [http://www.w3.org/TR/owl-guide/ OWL Web Ontology Language Guide], W3C Recommendation 10 February 2004
* [http://www.w3.org/TR/owl-absyn/ OWL Web Ontology Language Semantics and Abstract Syntax], W3C Recommendation 10 February 2004
* Dean M., Schreiber G (Editors); van Harmelen F., Hendler J., Horrocks I., McGuinness D.L., Patel-Schneider P.F., Stein L.A. (Authors), ''OWL Web Ontology Language Reference'', W3C Recommendation, 10 February 2004. [http://www.w3.org/TR/owl-ref/ HTML]

; Other RDF Applications
* [http://www.w3.org/TR/rdf-sparql-query/ SPARQL Query Language for RDF] (W3C Recommendation, 15 January 2008)
* [http://www.w3.org/PICS/ PICS] (Platform for Internet Content Selection)
* [http://www.w3.org/TR/skos-reference/ SKOS Simple Knowledge Organization System] (W3C WD Jan 2008)

=== Overviews ===

* [http://www.mozilla.org/rdf/doc/index.html Mozilla's RDF pointers]
* [http://www.oasis-open.org/cover/rdf.html Oasis Resource Description Framework (RDF)]
* [http://www.w3.org/TR/NOTE-rdfarch W3C Data Formats] A older (1997) note on the planned XML-centered framework
* Chris Waterson, [http://developer.mozilla.org/en/docs/RDF_in_Fifty_Words_or_Less RDF in Fifty Words or Less], Mozilla Magazine.

=== On-line validation ===

* [http://www.w3.org/RDF/Validator/ W3C RDF validation service]

=== RDF-related web sites ===

* http://www.semanticplanet.com/
* W3C [http://www.w3.org/2001/sw/ Semantic Web] page.
* [http://ontoworld.org/ ontoworld.org]

=== Various to sort out ===

* [http://www-4.ibm.com/software/developer/library/ws-rdf/index.html?dwzone=ws Supercharging WSDL with RDF Managing structured Web service metadata] article by Uche Obbuji
* [http://www.ilrt.bris.ac.uk/discovery/rdf-dev/rudolf/rdfviz/ Rudolf: RDFViz] Exploring tools for RDF Graph Visualisation by Dan Brickely, project page.

== References ==

* Eric Miller An Introductionto the Resource Description Framework (1998), ''[http://www.dlib.org/dlib/may98/05contents.html D-Lib Magazine]'' May 1998, ISSN 1082-9873, [http://www.dlib.org/dlib/may98/miller/05miller.html HTML]

* Manola Frank and Eric Miller (2004). [http://www.w3.org/TR/rdf-primer/ RDF Primer], W3C Recommendation 10 February 2004, ''W3C''.

[[Category: Standards]]
[[Category: XML]][[Category:web standards]]
[[Category: Knowledge representation]]

RDF - Revision history

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