Answer sets for consistent query answering in inconsistent databases

TLDR

A relational database is inconsistent when it violates integrity constraints, yet most of its data typically remains consistent with those constraints. The paper applies answer set logic programming to retrieve consistent information from possibly inconsistent databases. The approach specifies database repairs using disjunctive logic programs with exceptions, employing answer set semantics to preserve data persistence by default while allowing exceptions to restore consistency, with a focus on binary integrity constraints common in practice.

Abstract

A relational database is inconsistent if it does not satisfy a given set of integrity constraints. Nevertheless, it is likely that most of the data in it is consistent with the constraints. In this paper we apply logic programming based on answer sets to the problem of retrieving consistent information from a possibly inconsistent database. Since consistent information persists from the original database to every of its minimal repairs, the approach is based on a specification of database repairs using disjunctive logic programs with exceptions, whose answer set semantics can be represented and computed by systems that implement stable model semantics. These programs allow us to declare persistence by default of data from the original instance to the repairs; and changes to restore consistency, by exceptions. We concentrate mainly on logic programs for binary integrity constraints, among which we find most of the integrity constraints found in practice.