Reactive planning using a `situation space´

The problem of how to plan in tactical situations (such as anti-submarine warfare) where planning must be responsible to events, or other agent´s actions, which lie outside the predictive capability of the planner is addressed. The basic difficulty presented by this type of planning problem is how to engage in actions that are coherently related to the achievement of the overall goal despite the fact that often the planner cannot develop a complete plan for achieving that overall goal. To overcome this difficulty, the authors have developed a planning model within which the planner is controlled by knowledge organized into what is termed a situation space. The situation space guides the selection of goals and the construction of complete subplans which are appropriate to situations that arise and are coherently related to the overall goal. The situation space supports the principled generation of plan failure and replanning in a reactive environment