Harry Chen's Context Broker Architecture (CoBrA) provides situational awareness for a group of sensors, devices, and other information systems. The list of ontologies used by CoBrA gives you an idea of what can be reasoned by the system: device, location, context, and many more. Chen's quicktime demo shows the CoBrA rejecting facts which do not fit into its contextual state, as well as a visual representation of the RDF data involved (by way of Danny Ayers).