[bsb]

There's also Stardog (stardog.com), from the makers of the Pellet OWL reasoner, which just entered this space. AllegoGraph is pretty cool, one of the best examples of commercial LISP success, and they have a pretty rich ecosystem around AllegroGraph (Jena, Sesame, etc support).

[mark_l_watson]

I have tried out two beta versions of StarDog, which is also very nice. If you ask, I think that they will provide you with the beta system.

[bsb]

already on the beta list ;)