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Journal of Logic and Computation, Volume 11, Issue 4, pp. 499-525: Abstract.

Nonmonotonic Inheritance in Object-Oriented Deductive Database Languages

Wolfgang May, and Paul-Thomas Kandzia

Institut für Informatik, Universität Freiburg, Germany. E-mail: {may,kandzia}@informatik.uni-freiburg.de

Deductive object-oriented frameworks integrate logic rules and inheritance. There, specific problems arise: due to the combination of deduction and inheritance, (a) deduction can take place depending on inherited facts, thus raising indirect conflicts, and (b) also the class hierarchy and -membership is subject to deduction. From this point of view, we investigate the application of the extension semantics of Default Logic to deductive object-oriented database languages. By restricting the problem to Horn programs and a special type of defaults tailored to the semantics of inheritance, a forward-chaining construction of a Herbrand-style representation of extensions is possible. This construction is compared with the semantics for F-Logic (and implemented in the FLORID system) which is based on a combination of classical deductive fixpoints and an inheritance-trigger mechanism. We show that the F-Logic semantics coincides with the standard semantics of Default Logic and Inheritance Networks.

Keywords: Nonmonotonic reasoning, inheritance, logic programming, default logic, F-, logic, object-, oriented deductive databases

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