RDF

From EduTech Wiki
Jump to: navigation, search

This article or section is a stub. A stub is an entry that did not yet receive substantial attention from editors, and as such does not yet contain enough information to be considered a real article. In other words, it is a short or insufficient piece of information and requires additions.

Draft

1 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.

2 Major RDF vocabularies

Metadata
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)

3 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:

A simple ressource-author relationship

4 RDF and the semantic web

4.1 The RDF Software stack

The RDF software stack

4.2 The RDF bus

Software clients of the RDF bus

5 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" (Turtle - Terse RDF Triple Language, retrieved 15:31, 10 March 2008 (MET)).

Example:

<?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>

becomes in turtle syntax:

@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/>
  ] .

6 Links

6.1 Standards

RDF Namespaces
RDF and XHTML
OWL
Other RDF Applications

6.2 Overviews

6.3 On-line validation

6.4 RDF-related web sites

6.5 Various to sort out

7 References

  • Eric Miller An Introductionto the Resource Description Framework (1998), D-Lib Magazine May 1998, ISSN 1082-9873, HTML
  • Manola Frank and Eric Miller (2004). RDF Primer, W3C Recommendation 10 February 2004, W3C.