Preference-based planning
In artificial intelligence, preference-based planning is a form of automated planning and scheduling which focuses on producing plans that achieve outcomes in a way that also satisfies user-specified preferences insofar as possible. In many problem domains, a task can be accomplished by various sequences of actions (also known as plans). These plans can however vary in quality: there can be many ways to solve a problem but one generally prefers a way that is, e.g., cost-effective, quick and safe.
Preference-based planners take these preferences into account when producing a plan for a given problem. The Planning Domain Definition Language supports the specification of preferences through preference statements: for example, the statement (preference (always (clean room1))) indicates that the user prefers that room1 should be clean at each state of the plan. In other words, the planner should not schedule an action that causes room1 to become dirty.
Examples of preference-based planning software include PPLAN[1] and HTNPlan-P[2] (preference-based HTN planning).