Reference: Fadel, R. M. Planning with Complex Actions. 2002.
Abstract: In this thesis we propose a framework to represent complex actions as primitive operators and plan with them. In particular, we provide semantically-justified definitions and characterizations of the preconditions and conditional effects of complex actions, and we prove the soundness and completeness of planning using complex actions with respect to planning in the initial primitive action domain. The representation of complex actions as primitive operators is relevant in the case of Web services, since the latter can often be represented as complex actions, but do not have a priori explicit preconditions or effects, which is needed in order to plan with them using operator-based techniques. Based on this representation, our framework of planning with complex actions is interesting in classical operator-based planning because it allows the use of relevant conditional subplans, potentially reducing the search space. Using the results of this thesis, we present an algorithm of a compiler that computes the preconditions and effects of a restricted class of complex actions, with the domain being represented in a PDDL-equivalent form. We present experimental results which show a dramatic improvement in automatic plan generation when using complex actions. We use the situation calculus and Golog to formalize the task and our solution.
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