Resource Description Framework (RDF)

The "Resource Description Framework" (RDF)  is a conceptual framework supported by some accessory technologies that together help build what is called the "semantic web".

The conceptual framework is based on a very simple assumption: "triples" constituted by a subject. a predicate and an object can represent and describe everything. In the RDF model, subject and object are entities, or instances of "classes", while predicates are "properties".

Example:

<resource A> – <has title> – “War and Peace”
<resource A> - <has author> - <person A>
<person A> - <has name> - “Lev Tolstoj”

Reducing metadata to this essential structure eliminates a certain degree of incoherence and arbitrariness that is often found in the definition of metadata structures, adding more rigor to the model that has to be followed in describing things. Besides, the basic concept that subject and object should be represented as often as possible by URIs (Uniform Resource Identifiers) gives the possibility to identify entities univocally in different records, thus allowing to interlink records across sources and expand searches navigating through URIs.

For predicates/properties, any metadata set identifiable through a namespace URI can be used. For subjects and objects, beside literals, URIs identifying entities should be used, preferably from widely used KOS and authority data sources that are exposed as RDF.

RDF can be serialized in different ways: graphs (human-readable), RDF, N3, Json…

Fig. 2.1. (from http://www.w3.org/Submission/rdfsource/):
An RDF "graph" stating that a resource has a title ("RDF Source") and a creator and that this creator is of type Person and has a name ("Fabien Gandon") and a mailbox ("mailto:fgandon@inria.fr")

 

The corresponding triples would be:

Subject
Predicate
Object
<http://www-sop.inria.fr/edelweiss/fabien/docs/w3c/rdfsource/rdfsource.html>
dc:title
"RDF Source"
<http://www-sop.inria.fr/edelweiss/fabien/docs/w3c/rdfsource/rdfsource.html>
dc:creator
<http://ns.inria.fr/fabien.gandon
/foaf#me>
<http://ns.inria.fr/fabien.gandon/foaf#me>     
rdf:type   
foaf:Person
<http://ns.inria.fr/fabien.gandon/foaf#me>    
foaf:name  
"Fabien Gandon"

 


A possible representation of this graph in RDF/XML:

More information on Wikipedia: http://en.wikipedia.org/wiki/Resource_Description_Framework