A Logic Programming Approach to Querying and Integrating P2P Deductive Databases

The paper proposes a logic framework for modeling the interaction among deductive databases and computing consistent answers to logic queries in a P2P environment. As usual, data are exchanged among peers by using logical rules, called mapping rules. The novelty of our approach is that only data not violating integrity constraints are exchanged. The (declarative) semantics of a P2P system is defined in terms of weak models. Under this semantics only facts not making the local databases inconsistent are imported, and the preferred weak models are those in which peers import maximal sets of facts not violating integrity constraints. An equivalent and alternative characterization of preferred weak model semantics, in terms of prioritized logic programs, is also introduced and the computational complexity of P2P logic queries is investigated.