Repairing and Querying: the Fundamental Decision Problems

Abstract

In this chapter, we introduce some fundamental decision problems related to repairing and querying inconsistent data. Specifically, we formalize the repair existence problem, the minimal repair checking problem, and the consistent query answer problem, and analyze their computational complexity in the presence of databases inconsistent w.r.t. a given set of aggregate constraints. In this regard, we provide a thorough characterization, as we investigate the sensitivity of the computational complexity of these problems to several aspects: the domain of numerical attributes (integers or rationals), the form of the aggregate constraints considered (steady or not), and the minimality semantics (card- or set-minimal).