Stratification-based Criteria for Checking Chase Termination.

Several database areas such as data exchange and integration share the problem of fixing database instance violations with respect to a set of constraints. The chase algorithm solves such violations by inserting tuples and setting the value of nulls. Unfortunately, the chase algorithm may not terminate and the problem of deciding whether the chase process terminates is undecidable. Recently there has been an increasing interest in the identification of sufficient structural properties of constraints which guarantee that the chase algorithm terminates. In this paper we present more general criteria for chase termination. We first present extensions of the well-known stratification condition and, then, introduce a new criterion, called local stratification (LS), which generalizes both super-weak acyclicity and stratification-based criteria (including the class of constraints which are inductively restricted).