The extended closed world assumption and its relationship to parallel circumscription
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
Logic and Databases: A Deductive Approach
ACM Computing Surveys (CSUR)
On Indefinite Databases and the Closed World Assumption
Proceedings of the 6th Conference on Automated Deduction
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We describe a decidable algorithm to answer queries in circumscriptive theories, that allows the use of variable predicates. This significantly extends the results obtained in our earlier paper [P], where a similar algorithm was constructed for circumscriptive theories without variable predicates.Since prioritized circumscription is equivalent to a conjunction of parallel circumscriptions with variables, the algorithm can be used to answer queries in theories circumscribed by prioritized circumscription. The Closed-World Assumption (CWA) and its generalization, the Extended Closed-World Assumption (ECWA), can be considered as a special form of circumscription. Consequently, our method also applies to answering queries in theories using the Closed-World Assumption or its generalizations.For the sake of clarity, we restrict our attention to theories consisting of ground clauses. Our algorithm, however, has a natural extension to theories consisting of arbitrary clauses.