Inconsistency-tolerant database repairs and simplified repair checking by measure-based integrity checking

Abstract

Database states may be inconsistent, i.e., their integrity may be violated. Database repairs are updates such that all integrity constraints become satisfied, while keeping the necessary changes to a minimum. Updates intending to repair inconsistency may go wrong. Repair checking is to find out if a given update is a repair, i.e., if the updated state is free of integrity violations and if the changes are minimal. However, integrity violations may be numerous, complex or opaque, so that attaining a complete absence of inconsistency is not realistic. We discuss inconsistency-tolerant concepts of repair and repair checking. Repairs are no longer asked to be total, i.e., only some but not all inconsistency is supposed to disappear by a repair. For checking if an update reduces the amount of inconsistency, integrity violations need to be comparable. For that, we use measure-based integrity checking. Both the inconsistency reduction and the minimality of inconsistency-tolerant repair candidates can be verified or falsified by measure-based integrity checkers that simplify the evaluation of constraints. As opposed to total repair checking, which evaluates integrity constraints brute-force, simplified repair checking exploits the incrementality of updates.