Re: RDF Graphs

>     Formally, an RDF graph is a *set* of RDF triples, and an RDF
>     triple is a 3-element *sequence* comprising a subject which is an
>     IRI or a blank node, a property which is a IRI and an object which
>     is an IRI, a blank node or a literal; for definitions of 'blank
>     node' and 'literal', see
>     http://www.w3.org/TR/rdf11-concepts/#section-rdf-graph
>
>     So, long story short: an RDF graph is a set.
>

The first version of SPARQL implied bag semantics, but all theoretical
treatments of RDF use set semantics.
However, most RDF stores implement a variation of this model where RDF
graphs are bags of RDF triples.

Cheers,
Kostis