Certain Answers for Views and Queries Expressed as Non-recursive Datalog Programs with Negation

* Final gross prices may vary according to local VAT.

Get Access

Abstract

In this paper, we study the problem to compute certain answers in case when view definitions are expressed as non-recursive datalog programs with negation and queries are expressed as semi-positive non-recursive datalog programs with negation. Two situations are analyzed: the open world assumption (OWA) and the close world assumption (CWA). Associated to a view, and an extension of the view, a tree is constructed, which is useful to specify a method to compute certain answers.