Planningand Replanning of Large - Scale Activities ( Preliminary Report )

EEciency dictates that plans for large-scale distributed activities be revised incrementally, with parts of plans being revised only if the expected utility of identifying and revising the subplans improve on the expected utility of using the original plan. The problems of identifying and reconsidering the subplans aaected by changed circumstances or goals are closely related to the problems of revising beliefs as new or changed information is gained. But the current techniques of reason maintenance| the standard method for belief revision|choose revisions arbitrarily and enforce global notions of consistency and groundedness which may mean reconsidering all beliefs or plan elements at each step. We outline revision methods that revise only those beliefs and plans worth revising, and that tolerate incoherence and ungroundedness when these are judged less detrimental than a costly revision eeort.