• Link- Mozilla RDF

Updated: Sept 24 2007

It is a browser plugin, which introduces browser dependencies, but the project is Open Source and seems to be active and well-supported.

From the site:

Mozilla RDF was originally used to support the Aurora/Sidebar user interface and SmartBrowsing metadata services. It's main use in Mozilla now is as a common data model and API for use in XUL-based applications.

Im addition there is a sub-project for a Mozilla RDF Inference Engine. It is written in C/C++, so it should be able to run an inference engine about as well as it can, though possibly with a fairly restricted vocabulary/ontology ( to be determined ).