WonderWeb "We are on the brink of a new generation of World Wide Web (WWW) which, in his recent book Weaving the Web, Tim Berners-Lee calls the Semantic Web...The development of ontologies will be central to this effort. Ontologies are meta data, providing a controlled vocabulary of terms, each with an explicitly defined and machine processable semantics. By defining shared and common domain theories, ontologies help both people and machines to communicate more effectively."
OWL API with inferencing support. The comments on the RDF Interest scratchpad are not very positive. The best thing I can say is that the build scripts design is novel and difficult to get going (I gave up).