Preferential Semantics for Causal Fixpoints

In this paper we concentrate on the causal theory of action developed by McCain and Turner [2] for computing ramifications. Our aim here is to characterise this theory of action in terms of a preferentialstyle semantics in the spirit of Shoham [4]. Such a result would not only place McCain and Turner's theory in a uniform setting, facilitating comparison with other logics of action, but also give a clearer insight into the nature and behaviour of causality captured by their framework. We first show that this objective is not attainable via a traditional preferential semantics. However, preferential semantics is not abandoned entirely. Rather, it is augmented to arrive at the desired result. We maintain that two components — minimal change and causality — are essential in providing a (concise) solution to the frame and ramification problems.