A comparison of failure-handling approaches for planning systems—Replanning vs. recovery

摘要

A planning process formulates action assignments for various agents to accomplish a goal statement. In a real situation, unexpected environmental changes (called failures) may invalidate the preformulated plan. When a failure occurs, effective and efficient handling procedures must be taken to prevent irreversible damages. A failure-handling mechanism is a key component in a fault-tolerant system, which makes autonomous operation possible. There are two basic approaches to failure handling—replanning and recovery. In the replanning approach, the currently failure-encountered state is treated as a new initial state, and a brand-new plan is derived from scratch. On the other hand, the recovery approach preserves the applicable components of the original plan and makes necessary adjustments to the preserved plan components to fit the new state. This article presents a method of achieving recovery and compares its performance with replanning. In general, the recovery approach provides a better response time, and the replanning approach sometimes provides a better plan quality.