Data correspondence, exchange and repair

• Authors: Gösta Grahne;Adrian Onet
• Venue: Proceedings of the 13th International Conference on Database Theory
• Year: 2010

Checking the correspondence between two or more database instances and enforcing it is a procedure widely used in practice without however having been explored from a theoretical perspective. In this paper we formally introduce the data correspondence setting and its associated computational problems: checking the existence of solutions, and verifying whether a candidate is a solution, for three distinct types of solutions. Data correspondence is a generalization of data exchange and peer data exchange, and a special case of repairing inconsistent databases. We introduce a new class of dependencies, called semi-LAV, that properly includes both LAV and full dependencies, while retaining tractability for peer data exchange, data correspondence, and database repairs. We also introduce the concept of Σ-satisfying homomorphisms. This new type of homomorphism, together with recent advances, is essential in achieving tractability, while at the same time allowing a large class of dependencies, namely the aforementioned semi-LAV ones. We also show the intractability for a series of problems in the case of weakly acyclic tuple generating dependencies. This implies that many tractability results for weakly acyclic dependencies do not carry over to data correspondence; in these new settings we need to restrict the dependencies a bit further, yielding our semi-LAV dependencies.