Buying Time for Resource-Bounded Planning

To react appropriately in hard real-time environments, a system must either employ fast dynamic planning or recall a pre-built reactive response. For complex problems, real-time, accurate dynamic planning may be impossible, and the complete set of possible reactions may be too large to build and store in advance. In this paper, we propose combining offiine and online planning such that a set of offline plans are built and stored to maximize the amount of time available for any subsequent online planning. We explore this concept in CIRCA, the Cooperative Intelligent Real-time Control Architecture, which has concentrated on guaranteeing failure avoidance via a combination of planning, scheduling, and real-time plan execution. We are in the process of implementing a plan cache which will increase CIRCA’s overall likelihood of success in timeconstrained situations, and we illustrate potential gains from these modifications using a simple example from the fully-automated aircraft domain.