Conservative extensions in the lightweight description logic ε£

Abstract

We bring together two recent trends in description logic (DL): lightweight DLs in which the subsumption problem is tractable and conservative extensions as a central tool for formalizing notions of ontology design such as refinement and modularity. Our aim is to investigate conservative extensions as an automated reasoning problem for the basic tractable DL ε £. The main result is that deciding (deductive) conservative extensions is EXPTIME-complete, thus more difficult than subsumption in ε £, but not more difficult than subsumption in expressive DLs. We also show that if conservative extensions are defined model-theoretically, the associated decision problem for ε £ is undecidable. © Springer-Verlag Berlin Heidelberg 2007.