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 the semantics defined in [KLW95] 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.
Preliminary versions have been presented in