A New HTN Planning Framework for Agents in Dynamic Environments

In a dynamic environment, even if an agent makes a plan to obtain a goal, the environment might change while the agent is executing the plan. In that case, the plan, which was initially valid when it was made, might later become invalid. Furthermore, in the process of replanning, it is necessary to take into account the side effects of actions already executed . To solve this problem, we have previously presented an agent life cycle that interleaves HTN planning, action execution, knowledge updates, and plan modification. In that agent life cycle, the plans are always kept valid according to the most recent knowledge and situation. However, it deals with only total-order plans. This paper extends the agent life cycle so that the agent can handle partial-order plans.