Datalog extensions for tractable query answering over ontologies

Abstract

We survey a recently introduced family of expressive extensions of Datalog, called Datalog±, which is a new framework for representing ontologies in the form of integrity constraints, and for query answering under such constraints. Datalog± is derived from Datalog by allowing existentially quantified variables in rule heads, and by enforcing suitable properties in rule bodies, to ensure decidable and efficient query answering. We first present different languages in the Datalog± family, providing tight complexity bounds for nearly all cases. We then show that such languages are general enough to capture the most common tractable ontology languages. In particular, Datalog± can express the DL-Lite family of description logics and F-Logic Lite. Datalog± is a natural and very general framework that can be employed in different contexts such as data integration and exchange. © 2010 Springer-Verlag Berlin Heidelberg.