l14planchang

l14planchang - Total Order Plan <Actions[i] >...

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Self commanding Self diagnosing Self repairing Planning and Execution in a Changing World 1 Brian C. Williams 16.410/13 Session 14 Slides draw upon materials from: Dan Weld Stuart Russell & Peter Norvig dinner present cook wrap carry cleanH quiet noGarb cleanH dinner present Prop at 0 Action at 0 Prop at 1 Action at 1 Prop at 2 noop-dinner noop-present Total Order Plan <Actions[i] > Contains Irrelevant Committments Readings and Assignments • AIMA Chapter 12 • Blum and Furst, GraphPlan article • Problem Set #7 out, due November 9 th • 16.413 – Individual team reading folder – Final project guidelines dinner present cook wrap cleanH quiet noGarb cleanH dinner present Prop at 0 Action at 0 Prop at 1 Action at 1 Prop at 2 A Partial Order Plan <Actions, Orderings, Links> Removes What is Irrelevant Monitors Autonomous Agents Command dispatch Fault protection Attitude control Mission Goal Scenario Self - commanding Self - diagnosing Self - repairing RECOVERY PLANNING EXECUTION Commanded at: • Mission level • Engineering level Outline • Partial order planning in a nutshell • Plan execution • Plan monitoring • Conditional planning • Model-based programming of robust explorers • Reactive planning and hidden state
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Example Problem Go(HWS) Go(Home) Buy(Drill) Buy(Milk) Buy(Ban.) Go(SM) At(SM), Sells(SM,Milk) At(SM) At(SM), Sells(SM,Ban.) At(Home) At(HWS) At(HWS) Sells(HWS,Drill) Have(Milk) Have(Drill) Have(Ban) At(Home) At(HWS) At(SM) Initial State: Operators: Goal: Have(Milk) At(Home) Have(Ban.) Have(Drill) At(Home) Sells(HWS,Drill) Sells(SM,Milk) Sells(SM,Ban.) Partial Order Planning Algorithm The algorithm falls out of Consistency and Completeness Completeness: • Must achieve all preconditions ? Backward chain from goals to initial state by inserting actions and causal links. Must avoid intervening actions that threaten ? After each action is inserted, search for any action that threatens its effects, and impose ordering to resolve. Consistent: • Ordering must be consistent ? After each causal link and ordering is inserted, check for loops. Start Go(HWS) Go(Home) Finish Buy(Drill) Buy(Milk) Buy(Ban.) Go(SM) Have(Milk) At(Home) Have(Ban.) Have(Drill) At(SM), Sells(SM,Milk) At(SM) At(SM), Sells(SM,Ban.) At(Home) At(HWS) At(HWS) Sells(HWS,Drill) At(Home) Sells(HWS,Drill) Sells(SM,Milk) Sells(SM,Ban.) Partial Order Plan <Actions,Orderings,Links> POP(<A,O,L>, agenda, actions) <A,O,L>, A partial plan to expand Agenda: A queue of open conditions still to be satisfied: <p, a need > Actions: A set of actions that may be introduced to meet needs. a add : an action that produces the needed condition p for a need A threat : an action that might threaten a causal link from a producer to a consumer Correctness: A Complete and Consistent Plan • Complete Plan IFF every precondition of every step is achieved A step’s precondition is achieved iff • its the effect of some preceding step, • no possibly intervening step can undo it.
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l14planchang - Total Order Plan &lt;Actions[i] &gt;...

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