Consistent query answering under inclusion dependencies

For several reasons a database may not satisfy certain integrity constraints (ICs), for example, when it is the result of integrating several independent data sources. However, most likely most of the information in it is still consistent with the ICs; and could be retrieved when queries are answered. Consistent answers with respect to a set of ICs have been characterized as answers that can be obtained from every possible minimal repair of the database. In this paper we show and analyze how specify those repairs using disjunctive logic program with a stable model semantics in the presence of referential ICs. In this case, repairs are obtained by introduction of null values that do not propagate through other constraints, which makes the problem of consistent query answering decidable. We also present results about cases where the implementation of consistent query answering can be made more efficient due to the fact that the program can be simplified into a non-disjunctive program. Finally, we discuss several research issues around the implementation of system for retrieving consistent answers to queries from a DBMS.

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