Preference-based planning: Difference between revisions

Revision as of 12:05, 17 June 2010

Revision as of 12:09, 17 June 2010

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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 [[preference]]s insofar as possible. In many [[problem ___domain]]s, 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 specificationExamples of preferences through <code>preference</code>-based statements:planning forsoftware example,include the''PPLAN''<ref statement <codename="pplan">(preference[http://www.cs.toronto.edu/~sheila/PPLAN/ (always (clean room1)))PPLAN]</coderef> indicatesand that''HTNPlan-P''<ref the user prefers that <codename="htnplanp">room1<[http:/code> should be clean at each state of the plan/www.cs.toronto.edu/kr/publications/1242050782_Sohrabi-IJCAI09.pdf InHTN otherPlanning words, the planner should not schedule an action that causeswith <code>room1Preferences]</coderef> to(preference-based become[[Hierarchical dirtytask network|HTN planning]]).

== Overview ==

Preferences can be regarded as soft contraints on a plan. The quality of a plan increases when more preferences are satisfied but it may not be possible to satisfy all preferences in a single plan. This differs from hard constraints which must be satisfied in all plans produced by the planning software.

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The use of preferences may also increase the length of a plan in order to satisfy more preferences. For example, when planning a journey from home to school, the user may prefer to buy a cup of coffee along the way. The planning software could now plan to visit [[Starbucks]] first and then continue to school.<!-- please cite, I forgot which paper had this as example -->

== Planning Domain Definition Language ==

Examples of preference-based planning software include ''PPLAN''<ref name="pplan">[http://www.cs.toronto.edu/~sheila/PPLAN/ PPLAN]</ref> and ''HTNPlan-P''<ref name="htnplanp">[http://www.cs.toronto.edu/kr/publications/1242050782_Sohrabi-IJCAI09.pdf HTN Planning with Preferences]</ref> (preference-based [[Hierarchical task network|HTN planning]]).

The [[Planning Domain Definition Language]] supports the specification of preferences through <code>preference</code> statements: for example, the statement <code>(preference (always (clean room1)))</code> indicates that the user prefers that <code>room1</code> should be clean at each state of the plan. In other words, the planner should not schedule an action that causes <code>room1</code> to become dirty.

==References==