Pushing the EL Envelope

Abstract

Recently, it has been shown that the small DL EL, which allows for conjunction and existential restrictions, has better algorithmic properties than its counterpart FL₀, which allows for conjunction and value restrictions. Whereas the subsumption problem in FL₀ becomes already intractable in the presence of aclyc TBoxes, it remains tractable in EL even w.r.t. general concept inclusion axioms (GCIs). On the one hand, we will extend the positive result for EL by identifying a set of expressive means that can be added to EL without sacrificing tractability. On the other hand, we will show that basically all other additions of typical DL constructors to EL with GCIs make subsumption intractable, and in most cases even EXPTIME-complete. In addition, we will show that subsumption in FL₀ with GCIs is EXPTIME-complete.