RDF benchmarks

Does anyone know of any benchmarks for RDF query systems and/or
repositories?  I'd like to have some standard measure of (at least): (a)
triple insertion/deletion time, and (b) query performance against a sizeable
kb (with and without inference).  I'd guess that the systems out there today
vary enough in their capabilities that a single benchmark might be difficult
to come up with, so I imagine some categorization of benchmarks and results
would be necessary.

Thanks for any info or comments.

-Geoff Chappell