Skeptical Query-Answering in Constrained Default Logic

An approach to skeptical query-answering in Constrained Default Logic based on the Connection Method is presented. We adapt a recently proposed general method to skeptical reasoning in Default Logics—a method which does neither strictly require the inspection of all extensions nor the computation of entire extensions to decide whether a formula is skeptically entailed. We combine this method with a credulous reasoner which uses the Connection Method as the underlying calculus for classical logic. Furthermore, we develop the notion of a skeptical default proof and show how such a proof can be extracted whenever our calculus proves skeptical entailment of a particular query.