Queries over multiple graphs

In recent discussions over email and on IRC this morning we hit a
difference of implementation in some RDF storage systems.

In my system if you load multiple graphs with distinct source information
and the same statement appears in 2 graphs there are two distinct
statements. The same goes for statements that may be inferred by multiple
routes.

However in Andy's implementation this is not the case, meaning that
queries such as

SELECT ?s ?p ?o WHERE (?s ?p ?o)

will return different results.

Which of these is alloed depends on wether DAWG RDF systems are required
to RDF merge all the graphs they load.

- Steve