Conjunctive Query Inseparability of OWL 2 QL TBoxes


  • Boris Konev University of Liverpool
  • Roman Kontchakov Birkbeck College London
  • Michel Ludwig University of Liverpool
  • Thomas Schneider University of Bremen
  • Frank Wolter University of Liverpool
  • Michael Zakharyaschev Birkbeck College London


The OWL 2 profile OWL 2 QL, based on the DL-Lite family of description logics, is emerging as a major language for developing new ontologies and approximating the existing ones. Its main application is ontology-based data access, where ontologies are used to provide background knowledge for answering queries over data. We investigate the corresponding notion of query inseparability (or equivalence) for OWL 2 QL ontologies and show that deciding query inseparability is PSPACE-hard and in EXPTIME. We give polynomial time (incomplete) algorithms and demonstrate by experiments that they can be used for practical module extraction.




How to Cite

Konev, B., Kontchakov, R., Ludwig, M., Schneider, T., Wolter, F., & Zakharyaschev, M. (2011). Conjunctive Query Inseparability of OWL 2 QL TBoxes. Proceedings of the AAAI Conference on Artificial Intelligence, 25(1), 221-226. Retrieved from



AAAI Technical Track: Knowledge Representation and Reasoning