Querying Disjunctive Database Through Nonmonotonic Logics

Piero A. Bonatti, Thomas Eiter

Abstract: In this paper we study the expressive power of major nonmonotonic formalisms — among them circumscription, default logic, and autoepistemic logic — used as query languages over disjunctive databases. For this aim, we define the semantics of query expressions formulated in different nonmonotonic logics. The expressive power of the languages that we consider has been explored in the context of relational databases. Here, we extend this study to disjunctive databases; as a result, we obtain a finer-grained characterization of the expressive capabilities of those languages and interesting fragments thereof.