• Resource Description Framework
  • Language for representing metadata about resources on the WWW.
  • Intended for solutions in which the information needs to be processed by applications.
  • Represent simple statements about resources in terms of simple propertiesand property values.
  • RDF also provides an XML-based syntax called RDF/XML for recording and exchanging the ‘graphs.’
  • Based on the idea that things being described have properties which have values, and that resources can be described by making statements that specify those properties and values.
  • Concepts:
    • Subject - URL
    • Predicate - Property
    • Object - Value
  • RDF uses URIs as the basis of its mechanism for identifying subjects, predicates and objects
  • Triples notation
http://www.example.org/index.html has a creator whose value is John Smith
  • URIRef useful for objects, better identification. Provides fully-fledged resource. Can add more RDF statements using URIRef Object as Subject.
  • Also useful because it defines the type of use. e.g. define variable name vs human name.
  • Note people can use different URIs to refer to the same thing. Best to use an already-defined vocabulary.
  • RDF applies no intrinsic meaning to any data. It only describes the relationships.
  • Structured information is described by making a new Subject node. URIRef identifies the parent - aggregate concepts.
  • This can apparently also be done with a blank node (undefined object for aggregate parent).
    • Triples notation uses format _:whatever to denote differentiated blank nodes.
    • Blank node identifiers cannot be used as inter-graph identifiers. Cannot be used as predicates.
    • Useful to make statements about resources which don’t have URIs, but are described in terms of relationships with other resources which do have URIs.
  • RDF only describes binary relationships. To describe n-ary relationships, it must be broken up into a group of separate binary relationships.
  • Typed literals denote a datatype e.g. exterms:age “27”^^xsd:integer
  • This can be a URIref
  • RDF itself does not confirm the validity of the datatype

##Sources

  • RDF Primer - http://www.w3.org/TR/rdf-primer/