Default reasoning via blocking sets

Abstract

We present a new approach to reasoning with default logic that aims at Reiter's original approach, whenever there is no source for incoherence. We accomplish this by shifting the emphasis from the application of individual default rules to that of the joint application of a default rule together with rules supporting this application. This allows for reasoning in an incremental yet compositional fashion, without giving up the expressiveness needed for knowledge representation. Technically, our approach differs from others in that it guarantees the existence of extensions without requiring semi-monotonicity.