Querying Inconsistent Databases

In this paper we consider the problem of answering queries consistently in the presence of inconsistent data, i.e. data violating integrity constraints. We propose a technique based on the rewriting of integrity constraints into disjunctive rules with two different forms of negation (negation as failure and classical negation). The disjunctive program can be used i) to generate ‘repairs’ for the database and ii) to produce consistent answers, i.e. maximal set of atoms which do not violate the constraints. We show that our technique is sound, complete and more general than techniques previously proposed.