The SPARQL endpoint is http://wdqs-beta.wmflabs.org/bigdata/namespace/wdq/sparql and it has a Web form to fire queries. However http://www.wikidata.org/prop/direct/P31 (« instance of ») tells you what the entity is.

The repository doesn’t have named graphs, or at least the SPARQL endpoint rejects graph queries. The classes of entities (rdf:type) are not described in the repository.