Representation of Partial Knowledge and Query Answering in Locally Complete Databases
The Local Closed-World Assumption (LCWA) is a generalization of Reiter’s Closed-World Assumption (CWA) for relational databases that may be incomplete. Two basic questions that are related to this assumption are: (1) how to represent the fact that only part of the information is known to be complete, and (2) how to properly reason with this information, that is: how to determine whether an answer to a database query is complete even though the database information is incomplete. In this paper we concentrate on the second issue based on a treatment of the first issue developed in earlier work of the authors. For this we consider a fixpoint semantics for declarative theories that represent locally complete databases. This semantics is based on 3-valued interpretations that allow to distinguish between the certain and possible consequences of the database’s theory.
KeywordsRelational Database Predicate Symbol Partial Knowledge Ground Atom Deductive Database
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- 1.Abiteboul, S., Duschka, O.M.: Complexity of answering queries using materialized views. In: Proc. 17th PODS, pp. 254–263 (1998)Google Scholar
- 2.Cortés-Calabuig, A., Denecker, M., Arieli, O., Bruynooghe, M.: Representation of partial knowledge and query answering in locally complete databases. Technical Report 457, Department of Computer Science, K.U. Leuven, August 2006 (2006)Google Scholar
- 5.Doherty, P., Łukaszewicz, W., Szalas, A.: Efficient reasoning using the local closed-world assumption. In: Computational Logic: Logic Programming and Beyond. LNCS, vol. 2407, pp. 49–58. Springer, Heidelberg (2000)Google Scholar
- 7.Gelfond, M., Lifschitz, V.: Logic programs with classical negation. In: Proc. 7th ICLP, pp. 579–597 (1990)Google Scholar
- 9.Grahne, G.: Information integration and incomplete information. IEEE Data Engineering Bulletin 25(3), 46–52 (2002)Google Scholar
- 10.Lenzerini, M.: Data integration: A theoretical perspective. In: Proc. 21st PODS, pp. 233–246 (2002)Google Scholar
- 11.Levy, A.Y.: Obtaining complete answers from incomplete databases. In: Proc. 22nd VLDB, pp. 402–412 (1996)Google Scholar
- 13.Reiter, R.: Towards a logical reconstruction of relational database theory. In: Conceptual Modelling, pp. 191–233 (1982)Google Scholar