An Argumentation-theoretic Approach to Reasoning with Specificity

We present a new argumentation-theoretic approach to default reasoning with speci-city. The new approach diiers from other approaches in the way priority between defaults is handled. Here, it is context sensitive rather than context independent as in other approaches. We start by showing that any context independent handling of priorities between defaults as advocated in the literature until now is not suucient to capture general defeasible inheritance reasoning. This motivates the introduction of an argu-mentation framework for default reasoning with speciicity where the context sensitive priorities between defaults are captured by the attacks-relation between the arguments. We present several new and novel results. First we show that our framework subsumes the semantics of defeasible inheritance networks. We then show that the new semantics satisses core properties of default reasoning such as the conditioning, deduction, reduction, and cumulative propositions 1. To give a proof procedure to our approach, we present a modular transformation from default theories into logic programs where the preferred semantics of the former coincides with the answer set semantics of the later.