Homer: Replanning

Description

• Certain conditions in the world are unrelated to the execution of a plan and some goals of a plan are only inconsequential side effects. For instance, if Homer's goal is to get the log, the location of the dock is not relavent to the plan and the final location of Homer is not an important goal. But it is the case that certain preconditions are protected because they are necessary to achieve a goal and certain goals are protected as necessary results of an activity.
• When a protected goal or precondition is violated, Homer initiates replanning to account for the change.
• In particular, whenever a fact is terminated Homer will check if any plans were involved in a protection relation with that fact. If so, any plan nodes that were involved with the fact will be "demoted" back to goals and replanning will occur.