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.