Abstract
Deductive question-answering systems generally evaluate queries under one of two possible assumptions which we in this paper refer to as the open and closed world assumptions. The open world assumption corresponds to the usual first order approach to query evaluation: Given a data base DB and a query Q, the only answers to Q are those which obtain from proofs of Q given DB as hypotheses. Under the closed world assumption, certain answers are admitted as a result of failure to find a proof. More specifically, if no proof of a positive ground literal exists, then the negation of that literal is assumed true.
In this paper, we show that closed world evaluation of an arbitrary query may be reduced to open world evaluation of so-called atomic queries. We then show that the closed world assumption can lead to inconsistencies, but for Horn data bases no such inconsistencies can arise. Finally, we show how for Horn data bases under the closed world assumption purely negative clauses are irrelevant for deductive retrieval and function instead as integrity constraints.
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References
Clark, K.L. [1978] Negation as Failure, In Logic and Data Bases (H. Gallaire and J. Minker, Eds.), Plenum Press, New York, N.Y., 1978, 293–322.
Codd, E.F. [1972] Relational Completeness of Data Base Sublanguages, In Data Base Systems (R. Rustin, Ed.), Prentice-Hall, Englewood Cliffs, N.J., 1972, 65–98.
Henschen, L. and Wos, L. [1974] Unit Refutations and Horn Sets, JACM 21, 4 (October 1974), 590–605.
Hewitt, C. [1972] Description and Theoretical Analysis (Using Schemata) of PLANNER: A Language for Proving Theorems and Manipulating Models in a Robot, AI Memo No. 251, MIT Project MAC., Cambridge, Mass., April 1972.
Nicolas, J.M. and Gallaire, H. [1978] Data Bases: Theory vs. Interpretation, In Logic and Data Bases (H. Gallaire and J. Minker, Eds.), Plenum Press, New York, 1978, 33–54.
Nicolas, J. M. and Syre, J.C. [1974] Natural Question Answering and Automatic Deduction in the System Syntex, Proceedings IFIP Congress 1974, Stockholm, Sweden, August, 1974.
Reiter, R. [1977] An Approach to Deductive Question-Answering, BBN Report No. 3649, Bolt, Beranek and Newman, Inc., Cambridge, Mass., Sept. 1977.
Reiter, R. [1978] Deductive Question-Answering on Relational Data Bases, In Logic and Data Bases (H. Gallaire and J. Minker, Eds.), Plenum Press, New York, N.Y., 1978, 149–177.
Robinson, J. A. [1965] A Machine Oriented Logic Based on the Resolution Principle, JACM 12, (January 1965), 25–41.
Roussel, P. [1975] PROLOG: Manuel de Reference et d’Utilisation, Groupe dfIntelligence Artificielle, U.E.R. de Luminy, Universite d’Aix-Marseille, Sept. 1975.
van Emden, M. H. [1977] Computation and Deductive Information Retrieval, Dept. of Computer Science, University of Waterloo, Ont., Research Report CS-77–16, May 1977.
van Emden, H.H. and Kowalski, R.A. [1976] The Semantics of Predicate Logic as a Programming Language, JACM 23, (Oct. 1976), 733–742.
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Reiter, R. (1978). On Closed World Data Bases. In: Gallaire, H., Minker, J. (eds) Logic and Data Bases. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-3384-5_3
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DOI: https://doi.org/10.1007/978-1-4684-3384-5_3
Publisher Name: Springer, Boston, MA
Print ISBN: 978-1-4684-3386-9
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