Nonmonotonic Inheritance in Object-Oriented Deductive Database Languages

Wolfgang May , Paul-Th. Kandzia

Abstract:

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 a solution as implemented in the F-Logic system Florid which is based on a combination of classical deductive fixpoints and an inheritance-trigger mechanism.

From the F-Logic point of view, the main contribution of the report is to provide a connection between inheritance-canonic models as defined in [Kifer-Lausen-Wu-JACM-95] and classical AI frameworks.

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The full paper, Technical Report 114, Institut für Informatik, Universität Freiburg, Jan. 1999.

A revised version is published in Journal of Logic and Computation, 2000 (in Print)