RDF (Resource Description Framework) is a standard data model. It basically builds on anything being expressed as triples, i.e. statements of the form subject - predicate - object. An example is
<http://example.org/id/John> <http://example.org/id/Has_wife> <http://example.org/id/Mary>
saying that John has Mary as a wife (or, more exactly, that the property holds between the subject and the object).
- Help page on SPARQL
- Help page on using SPARQL and RDF stores
- RDF site at W3C (including specification)
- Wikipedia article on RDF