Exploiting Preferences over Information Sources to Efficiently Resolve Inconsistencies in Peer-to-peer Query Answering

Decentralized reasoning is receiving increasing attention due to the distributed nature of knowledge on the Web. We address the problem of answering queries to distributed propositional reasoners which may be mutually inconsistent. This paper provides a formal characterization of a prioritized peerto-peer query answering framework that exploits a preference ordering over the peers as well as a distributed entailment relation. We develop decentralized algorithms for computing answers to a restricted class of queries according to distributed entailment and prove their soundness and completeness. A heuristic exploiting the peers’ preference ordering for a more efficient computation of query answers from prioritized, inconsistent systems is also provided and its effectiveness empirically verified. We furthermore investigate global closed-world reasoning in our framework and show how our techniques can be used to achieve global generalized closedworld query answering from local closed-world reasoners in a restricted class of distributed peer-to-peer query answering systems.