We show that, although conjunctive queries over OWL 2 QL ontologies are reducible to database queries, no algorithm can construct such a reduction in polynomial time without changi...
Stanislav Kikot, Roman Kontchakov, Michael Zakhary...
We prove co-N2ExpTime-hardness for conjunctive query entailment in the description logic ALCOIF , thus improving the previously known 2ExpTime lower bound. The result transfers to ...
We present an optimized query rewriting algorithm for OWL 2 QL that computes the rewriting set of a user query by avoiding unnecessary inferences and extended clause subsumption ch...