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pl:prolog:pllib:means-ends_goal_protection [2019/06/27 15:50] |
pl:prolog:pllib:means-ends_goal_protection [2019/06/27 15:50] (aktualna) |
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| + | ====== Means-ends goal protection ====== | ||
| + | {{tag>planning}} | ||
| + | ===== Description ===== | ||
| + | A means-ends planner with goal protection. | ||
| + | |||
| + | **Source**: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7. | ||
| + | ===== Download ===== | ||
| + | Program source code: {{means-ends_goal_protection.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | % Figure 17.6 A means-ends planner with goal protection. | ||
| + | % Predicates satisfied, select, achieves and apply are as in Figure 17.5. | ||
| + | |||
| + | :- op( 900, fy, not). | ||
| + | |||
| + | % not Goal): negation as failure; | ||
| + | % Note: This is often available as a built-in predicate, | ||
| + | % often written as prefix operator "\+", e.g. \+ likes(mary,snakes) | ||
| + | |||
| + | not Goal :- | ||
| + | Goal, !, fail | ||
| + | ; | ||
| + | true. | ||
| + | |||
| + | % A means-ends planner with goal protection | ||
| + | |||
| + | plan( InitialState, Goals, Plan, FinalState) :- | ||
| + | plan( InitialState, Goals, [], Plan, FinalState). | ||
| + | |||
| + | % plan( InitialState, Goals, ProtectedGoals, Plan, FinalState): | ||
| + | % Goals true in FinalState, ProtectedGoals never destroyed by Plan | ||
| + | |||
| + | plan( State, Goals, _, [], State) :- | ||
| + | satisfied( State, Goals). % Goals true in State | ||
| + | |||
| + | plan( State, Goals, Protected, Plan, FinalState) :- | ||
| + | conc( PrePlan, [Action | PostPlan], Plan), % Divide plan | ||
| + | select( State, Goals, Goal), % Select an unsatisfied goal | ||
| + | achieves( Action, Goal), | ||
| + | can( Action, Condition), | ||
| + | preserves( Action, Protected), % Do not destroy protected goals | ||
| + | plan( State, Condition, Protected, PrePlan, MidState1), | ||
| + | apply( MidState1, Action, MidState2), | ||
| + | plan( MidState2, Goals, [Goal | Protected], PostPlan, FinalState). | ||
| + | |||
| + | % preserves( Action, Goals): Action does not destroy any one of Goals | ||
| + | |||
| + | preserves( Action, Goals) :- % Action does not destroy Goals | ||
| + | deletes( Action, Relations), | ||
| + | not (member( Goal, Relations), | ||
| + | member( Goal, Goals) ). | ||
| + | |||
| + | |||
| + | </code> | ||
| + | ===== Comments ===== | ||
