A general Datalog-based framework for tractable query answering over ontologies

  • Authors:

  • Andrea Calí;Georg Gottlob;Thomas Lukasiewicz

  • Affiliations:

  • Department of Computer Science and Information Systems, Birkbeck, University of London, UK and Oxford-Man Institute of Quantitative Finance, University of Oxford, UK;Department of Computer Science, University of Oxford, UK and Oxford-Man Institute of Quantitative Finance, University of Oxford, UK;Department of Computer Science, University of Oxford, UK

  • Venue:
  • Web Semantics: Science, Services and Agents on the World Wide Web
  • Year:
  • 2012

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Abstract

Ontologies and rules play a central role in the development of the Semantic Web. Recent research in this context focuses especially on highly scalable formalisms for the Web of Data, which may highly benefit from exploiting database technologies. In this paper, as a first step towards closing the gap between the Semantic Web and databases, we introduce a family of expressive extensions of Datalog, called Datalog^+/-, as a new paradigm for query answering over ontologies. The Datalog^+/- family admits existentially quantified variables in rule heads, and has suitable restrictions to ensure highly efficient ontology querying. We show in particular that Datalog^+/- encompasses and generalizes the tractable description logic EL and the DL-Lite family of tractable description logics, which are the most common tractable ontology languages in the context of the Semantic Web and databases. We also show how stratified negation can be added to Datalog^+/- while keeping ontology querying tractable. Furthermore, the Datalog^+/- family is of interest in its own right, and can, moreover, be used in various contexts such as data integration and data exchange. It paves the way for applying results from databases to the context of the Semantic Web.