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Towards More Expressive Ontology Languages: The Query Answering Problem

  • Speaker: Dr Andreas Pieris
  • Date: Wednesday, 18 January 2012 from 16:45 to 17:45
  • Location: Room 745, Malet Street

Ontology-based data access is a powerful form of extending database technology, where a classical extensional database is enhanced by an ontology that generates new intensional knowledge which may contribute to answer a query. The ontological integrity constraints for generating this intensional knowledge can be specified in description logics such as DL-Lite. It was shown that these formalisms allow for very efficient query answering w.r.t. the data complexity. They are, however, too weak to express simple and useful integrity constraints that involve joins. To overcome this limitation, a recently introduced family of Datalog-based languages, called Datalog+/-, which is a new framework for tractable ontology querying, uses tuple-generating dependencies as rules. In fact, Datalog+/- extends plain Datalog by features such as existentially quantified rule heads and, at the same time, restricts the rule syntax so as to achieve decidability of query answering. In this talk we present recent results on Datalog+/. In particular, a novel paradigm, called stickiness, ensuring tractability of query answering is discussed.

This is a joint work with Andrea Cali and Georg Gottlob.