Utilizing volatile external information during planning

There are many practical planning situations in which planners may need information from external sources during the planning process. We describe the following: . Wrappers that may be placed around conventional (isolated) planners. The wrapper replaces some of the planner's memory accesses with queries to external information sources. When appropriate, the wrapper will automatically backtrack the planner to a previous point in its operation. . Query-management strategies for wrappers. These dictate when to issue queries, and when/how to backtrack the planner. . Mathematical analysis and experimental tests. Our results show conditions under which different query management strategies are preferable, and demonstrate that certain kinds of planning paradigms are more suited than others for planning with volatile information.