We describe an extension of an OWL knowledge base using PostgreSQL, Jena, and Pellet with active rules in form of triggers. The triggers react on atomic events on the OWL level. In contrast to ``simple'' RDF triggers that can directly be mapped on updates on RDF triples, the extension to RDFS and OWL requires to combine reactivity with OWL reasoning. For this, ``direct'', pre-reasoning triggers that react on update operations (often also providing support for the intended operation), and ``indirect'', post-reasoning triggers that react on actual changes have to be distinguished. The approach has been implemented in a prototype based on the Jena framework.

[Slides (pdf)]

This research is supported by the EU FP6 Network of Excellence