replanning

Replanning is the process of updating or creating an alternative plan when the current plan becomes suboptimal or infeasible due to changes in objectives, constraints, or environment. It is used across domains including project management, operations research, artificial intelligence planning, robotics, logistics, and emergency response. Replanning can be proactive (planned review) or reactive (in response to events). Distinguish from contingency planning.

In practice, replanning involves monitoring progress, detecting deviations, diagnosing causes, generating candidate plans, and selecting and implementing a revised plan. Methods include rescheduling tasks, reallocating resources, changing sequencing, or altering objectives; in AI planning, plan repair or plan-space replanning; in robotics, online or dynamic replanning to accommodate moved obstacles.

Types and approaches: online replanning occurs in real time; tactical vs strategic replanning; automated planning tools may use optimization, constraint programming, heuristics, or simulated planning to compare alternatives. Uncertainty and incomplete information complicate replanning and may require robust or flexible plans.

Challenges and outcomes: key challenges include computational complexity, maintaining continuity, and avoiding thrashing from frequent changes. Benefits include maintaining alignment with goals, reducing risk and cost, and improving success probability. Examples: a software project revises its schedule after incoming requirements; an autonomous drone reroutes around a no-fly zone; a disaster-relief operation shifts from food distribution to water delivery as conditions change.