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39 lines
1.7 KiB
Markdown
39 lines
1.7 KiB
Markdown
# Spectra
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Spectra is a general purpose planning system. It extends STRIPS-style planning by allowing arbitray first-order formulae for state descriptions and background knowledge rather than just predicates. This allows, for instance, handling domains with infinite or unbounded objects elegantly (among other things).
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* Existing Planners are propositional
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* Drawbacks:
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* **Expressivity**: Cannot express arbitrary constraints. *“At every step make sure that no two blocks on the table have same color”*
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* **Domain Size**: Scaling to large domains of arbitrary sizes poses difficulty.
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# Architecture #
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# Example #
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# Scaling Up #
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Two approaches:
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1. **Procedural Attachments**: Special purpose procedural code that can bypass strict formal reasoning.
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2. *μ*-**methods**: Written in denotational proof language. Preserves soundness by letting us write down commonly used patterns of reasoning (a bit unwieldy integration now than the first approach)
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```clojure
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;; (removeFrom ?x ?y) => "Remove ?x from ?y"
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;; (placeInside ?x ?y) ==> "Place ?x inside ?y"
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(define-method planMethod [?b ?c ?d]
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{:goal [(In ?b ?c) (In ?c ?d)]
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:while [(In ?b ?d) (Empty ?c)
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(< (size ?c) (size ?d))
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(< (size ?b) (size ?c))]
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:actions [(removeFrom ?b ?d) (placeInside ?b ?c) (placeInside ?c ?d)]})
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Roughly, a method has conditions that the goal and background + start state should satisfy. If the conditions are satisfied, a plan template is generated (note the variables).
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The planner then verifies if the plan template works, if so it outputs the plan.
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```
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