On (in)tractability of OBDA with OWL 2 QL
Stanislav Kikot, Roman Kontchakov, Michael Zakharyaschev · BIROn (Birkbeck, University of London) · 2011
Abstract. 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 changing the data. On the other hand, we give a polynomial reduction for OWL 2 QL ontologies without role inclusions. 1