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An example of hierarchical planning… (1) planning a sequence of actions - N.B. not yet linguistic!

An example of hierarchical planning… (1) planning a sequence of actions - N.B. not yet linguistic!. A goal to be achieved by planning. Task: Ed wants to be in New York Formalization as a plan goal: be-at (Ed, New York) The algorithm: Top-down hierarchical planning

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An example of hierarchical planning… (1) planning a sequence of actions - N.B. not yet linguistic!

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  1. An example of hierarchical planning…(1) planning a sequence of actions- N.B. not yet linguistic!

  2. A goal to be achieved by planning • Task: • Ed wants to be in New York • Formalization as a plan goal: • be-at (Ed, New York) • The algorithm: Top-down hierarchical planning • Search our library of plan operators for ways of achieving the goal • For an operator to be usable, the preconditions much match the ‘state of the world’ • For an operator to be useful, the effect must leave us nearer to achieving our goal than we were before!

  3. Do we have a plan operator with a useful effect? be-at (Ed, New York)

  4. Our PLANOPERATORS… ?

  5. be-at (Ed, New York)

  6. be-at (Ed, New York)

  7. be-at (Ed, New York)

  8. be-at (Ed, New York)

  9. be-at (Ed, New York)

  10. Do we have a plan operator with a useful effect? be-at (Ed, New York)

  11. Our PLANOPERATORS… cost?time?

  12. This one looks promising, the planning process decides to take a closer look…

  13. be-at (Ed, NY) be-at (actor, destination) Matching or ‘unification’ We have a useful plan operator: so we ‘instantiate’ the operator Task goal: be-at (Ed, NY)

  14. ACTOR = Ed TRAIN=?train DESTINATION= NY

  15. Testing phase • Do the preconditions hold? • If not, we have to make them hold by planning further before we can carry out the action and get the desired effect • When the preconditions hold, we can achieve the effect by adding the actions in the body into our plan. This is the hierarchical expansion of the plan tree.

  16. Destination (?train, NY) On-board (Ed, ?train) Do the preconditions hold? ACTOR = Ed TRAIN=?train DESTINATION= NY

  17. So, can we plan some actions that will take the world to be nearer to how we want it? The preconditions do not yet match the world unfortunately… WORLD PRECONDITIONS Destination (?train, NY) On-board (Ed, ?train) Be-at (Ed, Washington)

  18. We set up some new goals (called ‘posting’) and see if we can plan for them to be achieved… PRECONDITIONS GOALS + Destination (?train, NY) On-board (Ed, ?train) • Lets us assume that there are lots of trains to NY from Washington, so the first goal can be filled in directly (‘be satisfied’) by looking in a database, e.g.: • destination (9am-train, NY) • destination (10am-train ,NY) • destination (11am-train, NY).

  19. We set up some new goals (called ‘posting’) and see if we can plan for them to be achieved… PRECONDITIONS GOALS Destination (?train, NY) On-board (Ed, ?train) • The second goal takes more work. We have to look in our plan library for operators with an effect that is relevant for: • On-board (Ed, 10am-train)

  20. Do we have a plan operator with a useful effect? On-board (Ed, 10am-train)

  21. On-board (Ed, 10am-train) ?

  22. On-board (Ed, 10am-train)

  23. On-board (Ed, 10am-train)

  24. On-board (Ed, 10am-train) This one looks promising, the planning process decides to take a closer look…

  25. ACTOR = Ed TRAIN= 10am-train

  26. Be-at (Ed, 10am-train) Have (Ed, ticket (10am-train)) Do the preconditions hold? ACTOR = Ed TRAIN=10-am-train

  27. So, can we plan some actions that will take the world to be nearer to how we want it? The preconditions do not yet match the world unfortunately… WORLD PRECONDITIONS Be-at (Ed, 10am-train) Have (Ed, ticket (10am-train)) Be-at (Ed, Washington) Further planning as above

  28. Resulting in a final complete hierarchical plan…

  29. A complete plan… • is a hierarchically organized sequence of actions • carrying out the actions in sequence will guarantee that the preconditions for achieving and subsequent effect are met in time • when all the sub-actions of a more abstract action have been performed, the abstract action has also been achieved and the corresponding effect also

  30. COMPLETE SUMMARY OF THE PLAN and PLAN LIBRARY(Bateman & Zock, 2003)

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