A conditional logic for planning and plan recognition

In much work in reasoning about action, an action is modelled as a function over world states. In this paper, we consider planning and plan recognition from the point of view of an approach to modelling actions as primitive semantic objects occurring in the situations of situation semantics. We argue that constraints as captured in a hierarchy of types of situations can form the basis of an agent's reasoning about action, and that the necessary constraints can be represented using a standard hierarchy of planning schemas. We present a conditional logic of constraints and show how both planning and plan recognition can be characterized as inference in the logic. We claim that our approach to formalizing action models the practice of existing planning systems more closely than traditional approaches.<<ETX>>