Browsing by Author "Arenas, M"

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    Answer sets for consistent query answering in inconsistent databases
    (2003) Arenas, M; Bertossi, L; Chomicki, J
    A relational database is inconsistent if it does not satisfy a given set of integrity constraints. Nevertheless, it is likely that most of the data in it is consistent with the constraints. In this paper we apply logic programming based on answer sets to the problem of retrieving consistent information from a possibly inconsistent database. Since consistent information persists from the original database to every of its minimal repairs, the approach is based on a specification of database repairs using disjunctive logic programs with exceptions, whose answer set semantics can be represented and computed by systems that implement stable model semantics. These programs allow us to declare persistence by default of data from the original instance to the repairs; and changes to restore consistency, by exceptions. We concentrate mainly on logic programs for binary integrity constraints, among which we find most of the integrity constraints found in practice.
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    SCDBR: An automated reasoner for specifications of database updates
    (1998) Bertossi, L; Arenas, M; Ferretti, C
    In this paper we describe SCDBR, a system that is able to reason automatically from specifications of database updates written in the situation calculus, a first-order language originally proposed by John McCarthy for reasoning about actions and change. The specifications handled by the system are written in the formalism proposed by Ray Reiter for solving the frame problem that appears when one expresses the effects on the database predicates of the execution of atomic transactions. SCDBR is written in PROLOG, and can solve several reasoning tasks, among others, it is able to derive the final specification from effect axioms, to answer queries to virtually updated databases, to check legality of transactions, to prove integrity constraints from the specification, to modify the specification in order to embed a desired integrity constraint, and to answer historical queries. For some of these tasks SCDBR can call other systems, like relational database systems, automated theorem provers, and constraint solvers.