Eric Jain defines RDF using Wikipedia's RDF definition: "Those close [...] become passionately committed to possibly insane projects, without regard to the practicality of the implementation or competitive forces in the marketplace."
Also, the Wikipedia definition of Resource Description Framework:
"A collection of RDF statements represents a labeled oriented pseudograph. As such, an RDF-based data model is more naturally suited to certain kinds of knowledge representation than the relational model and other ontological models traditionally used in computing today, although RDF data is often stored in relational databases, and as OWL demonstrates, ontologies can be built upon RDF."
And a pseudograph has: "...both multiple edges and loops. When stated without any qualification, a graph is almost always assumed to be simple."