Plan Impact Analysis involves detection of a replanning opportunity. Because an agent has limited resources and response time, computation has an associated cost. Of course, computation also has an intrinsic value, since presumably the more thought given to a problem, the better the solution. This module weighs the tradeoff and decides whether to invoke replanning or not. If it decides positively, it invokes Plan Modification Focusing. This module decides which search areas to reconsider, since replanning over the entire space is prohibitively expensive. Instead, plan subtrees within the dynamic influence diagrams of each execution architecture are examined, again weighing the benefit of replanning against the computational cost. Once a promising subregion is selected, Plan Modification begins. Modification of plans is identical to creation of plans, except that only subregions of the influence diagrams are used. Replanning continues until the Plan Impact Analysis module decides there's no longer any net benefit, in which case execution of the revised plan begins.