Incremental Integrity Checking: Limitations and Possibilities

Abstract

Abstract. Integrity checking is an essential means for the preservation of the intended semantics of a deductive database. Incrementality is the only feasible approach to checking and can be obtained with respect to given update patterns by exploiting query optimization techniques. By reducing the problem to query containment, we show that no procedure exists that always returns the best incremental test (aka simplification of integrity constraints), and this according to any reasonable criterion measuring the checking effort. In spite of this theoretical limitation, we develop an effective procedure allowing general parametric updates that, for given database classes, returns ideal simplifications and also applies to recursive databases. Finally, we point out the improvements with respect to previous methods based on an experimental evaluation.

On the difference between checking integrity constraints before or after updates

“…As opposed to that, to pre-test the feasibility of an update with respect to an integrity theory allows for avoiding both the execution of the update and, particularly, the restoration of the database state before the update, which may be very costly. Pre-test-based methods are, e.g., [48,50,78,54,55,25,37,66,24,64,65,59,60,22,61,58,23,26], including a few industrial attempts, e.g., [16,3]. Other methods provide simplifications that may require the availability of both the old and the new state, assuming that the database keeps track of the old state before committing an update, [82,83].…”