Under what conditions can query answering in OWL EL be done in PTIME?
Conjunctive query answering in OWL EL can be done in EXPTIME, and is PTIME-complete if the property hierarchy can be translated into a polynomially-sized nondeterministic finite automaton (https://www.w3.org/TR/owl2-profiles/#Computational_Properties). So, under what conditions can the property hierarchy be translated into a polynomially-sized nondeterministic finite automaton?