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INFORMATICA, 1998, Vol. 9, No. 1, 65-84
© Institute of Mathematics and Informatics, Vilnius, 1998

ISSN 0868-4952

Handling Termination in a Logical Language for Active Rules

Bertram LUDÄSCHER, Georg LAUSEN

Institut für Informatik Albert-Ludwigs-Universität Freiburg Am Flughafen 17, 79110 Freiburg i.Br., Germany E-mail: lausen@informatik.uni-freiburg.de

Abstract

Statelog is a Datalog extension integrating the declarative semantics of deductive rules with the possiblity to define updates in the style of active and production rules. The language is surprisingly simple, yet captures many essential features of active rules. After reviewing the basics of active rules, production rules, and deductive rules, we elaborate on the problem of handling rule termination in the context of Statelog: It is undecidable whether a Statelog program terminates for all databases, and PSPACE-complete for a given database. The latter can be accomplished within the logical language: for every Statelog program P, there is a terminating program P^\downarrow which decides for any given database \mathcal{D}, whether P\cup\db D terminates.

Keywords:

active databases
deductive databases
production rules
termination

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