Preference-based inconsistency-tolerant query answering under existential rules

Ontology-mediated query answering (OMQA) emerged as a paradigm to enhance querying of data sources with an ontology that encodes background knowledge. In applications involving large amounts from multiple sources, it might well be the case inconsistency arises, making standard useless, since everything is entailed by inconsistent knowledge base. Being able provide meaningful answers in presence thus critical issue make OMQA systems successful practice. The problem has attracted great deal interest over years. Different inconsistency-tolerant semantics have been proposed, is, approaches answer queries way despite at hand being inconsistent. Most literature are based on notion repair, “maximal” consistent subset database. general, there can several repairs, so often natural and desirable express preferences among them. this paper, we propose framework for bases under user existential rule languages. Specifically, introduce preference rules, declarative formalism which enable users (i) both database derived via ontology, (ii) preconditions hold. We then define two notions preferred repairs take rules into account. This naturally leads us introducing preference-aware counterparts popular semantics, where only considered answering. thorough analysis combined complexity different relevant problems wide range