Alert Generation in Execution Monitoring Using Resource Envelopes

A simple temporal network (STN) can often be used to represent the flexibility in the execution of a plan. Nodes represent the execution times of actions and directed edges represent constraints between them. An STN with resources (STNR) is an STN in which each node is associated with production or consumption levels of resources. The upper (lower) resource envelope of an STNR is the maximum (minimum) accumulated resource levels at every time instant over all possible executions. In this paper, we discuss the usefulness of resource envelopes in the context of execution monitoring. We show that they can be used in a tractable framework for forward projection of world states during plan execution. This allows an execution monitor to recognize depletion of resources early and to generate alerts with large look-aheads. It also supports retasking by enabling “what-if reasoning” during plan execution.