Deductive databases for computing certain and consistent answers from mediated data integration systems

We address the problem of retrieving certain and consistent answers to queries posed to a mediated data integration system under the local-as-view paradigm with open sources and conjunctive and disjunctive view definitions. For obtaining certain answers a query program is run under the cautious stable model semantics on top of a normal deductive database with choice operator that specifies the class of minimal legal instances of the integration system. This methodology works for all monotone Datalog queries. To compute answers to queries that are consistent with respect to given global integrity constraints, the specification of minimal legal instances is combined with another disjunctive deductive database that specifies the repairs of those legal instances. This allows to retrieve the answers to any Datalog¬ query that are consistent with respect to global universal and referential integrity constraints.