Prioritized Active Integrity Constraints for Database Maintenance

The paper presents a logic framework wherein constraints and preferences are used for database maintenance and querying. Our proposal is based on the use of a special type of integrity constraints (called Prioritized Active Integrity Constraints (PAICs)), whose body defines a constraint on data, whereas the head contains a set of partially ordered actions, which should be performed, if the body constraint is not satisfied, to make consistent the database. Therefore, a preference relation among repairs is introduced on the base of the (partially ordered) actions specified in the head of PAICs. On the base of the preference relation a set of preferred repairs is identified and preferred answers are derived from the database instances which have been made consistent by means of preferred repairs. The paper shows that databases with universal prioritized constraints admit (preferred) repairs and consistent answers if the set of constraints is satisfiable. The paper also shows how PAICs can be rewritten into disjunctive Datalog programs so that repairs can be obtained from the computation of stable models.