Reformulating Temporal Plans for Efficient Execution

The Simple Temporal Network formalism permits signiicant exibility in specifying the occurrence time of events in temporal plans. However, to retain this exibility during execution , there is a need to propagate the actual execution times of past events so that the occurrence windows of future events are adjusted appropriately. Unfortunately, this may run afoul of tight real-time control requirements that dictate extreme eeciency. The performance may be improved by restricting the propagation. However, a fast, locally propagating, execution controller may incorrectly execute a consistent plan. To resolve this dilemma, we identify a class of dis-patchable networks that are guaranteed to execute correctly under local propagation. We show that every consistent temporal plan can be reformulated as an equivalent dispatch-able network, and we present an algorithm that constructs such a network. Moreover, the constructed network is shown to have a minimum number of edges among all such networks. This algorithm will be own on an autonomous spacecraft as part of the Deep Space 1 Remote Agent experiment.

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