Pertinence Logic for Reasoning about Actions and Change

We discuss a new approach to dealing with causality in reasoning about actions and change. First, we introduce the logic of pertinence L 2 to describe knowledge over a static domain --especially the causal influences. Second, action execution and its direct and ramified effects are captured by the straightforward extension of L 2 to ACL 2 . We argue that reasoning with pertinence, as embodied in these languages, captures at once several aspects of reasoning about change hitherto treated separately. Moreover, pertinence makes deducing the effect of actions efficient, as shown by the implemented shell Medtool. 1 Introduction The aim of this paper is to introduce a new logic for commonsense reasoning about actions and change. This logic relies on an extended ontology that uses two simultaneous truthvalues for the formulas. Apart from the usual truth-values true and false, ft; fg, a formula will also have a pertinence "truth-value" being pertinent or non-pertinent, denoted fp; ng..