Reasoning about Typicality with Low Complexity Description Logics: The Logic εL+⊥T

We present an extension of the low complexity Description Logic epsilon L+perpendicular to for reasoning about prototypical properties and inheritance with exceptions. We add to epsilon L+perpendicular to a typicality operator T, which is intended to select the "most normal" instances of a concept. In the resulting logic, called epsilon L+perpendicular to T. the knowledge base may contain subsumption relations of the form "T(C) is subsumed by P", expressing that typical C-members have the property P. We show that the problem of entailment in epsilon L+perpendicular to T is in co-NP by proving a small model result.