Description Logic

"Orthogonal expressivity" of Pellet and Prolog?

Found a very interesting quote:

"Both OWL-DL and function-free Horn rules are decidable fragments of first-order logic with interesting, yet orthogonal expressive power"´╗┐Motik B, Sattler U, Studer R. Query Answering for OWL-DL with rules. Web Semantics: Science, Services and Agents on the World Wide Web. 2005;3(1):41-60. Available at:

"Horn rules", is what prolog builds upon (a prolog statement are horn rules, AFAIS), so maybe Prolog fits into the category of "function-free horn rules"? (Gotta try to figure that out), and OWL-DL is the W3C standard for expressive semantics, that reasoners like pellet (which is available in bioclipse build upon.

Reading tip: Quick overview of Prolog and it's role in Semantic Web

I Just read this paper on using thea for OWL (Web Ontology Language) reasoning from within Prolog.

Description Logic vs Prolog

Pellet, the reasoning system already integrated in Bioclipse, is based on so called "Description Logics".