Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Author: search.filters.author.Erol, KutluhanSubject: search.filters.subject.knowledge representation

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    A Critical Look at Critics in HTN Planning
    (1995) Erol, Kutluhan; Hendler, James A.; Nau, D.S.; Tsuneto, R.; ISR
    Detecting interactions and resolving conflicts in one of the key issues for generative planning systems. Hierarchical Task Network (HTN) planning systems use critics for this purpose. Critics have provided extra efficiency and flexibility to HTN planning systems, but their procedural -- and sometimes domain- specific - - nature has not been amenable to analytical studies. As a result, little work is available on the correctness or efficiency of critics. This paper describes a principled approach to handling conflicts, as implemented in UMCP, an HTN planning system. Critics in UMCP have desirable properties such as systematicity, and the preservation of soundness and completeness.
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    Complexity Results for HTN Planning
    (1995) Erol, Kutluhan; Hendler, James A.; Nau, D.S.; ISR
    Most practical work on AI planning systems during the last fifteen years has been based on hierarchical task network (HTN) decomposition, but until now, there has been very little analytical work on the properties of HTN planners. This paper describes how the complexity of HTN planning varies with various conditions on the task networks, and how it compares to STRIPS- style planning.

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    Semantics for Hierarchical Task-Network Planning
    (1995) Erol, Kutluhan; Hendler, James A.; Nau, Dana S.; ISR
    One big obstacle to understanding the nature of hierarchical task network (HTN) planning has been the lack of a clear theoretical framework. In particular, no one has yet presented a clear and concise HTN algorithm that is sound and complete. In this paper, we present a formal syntax and semantics for HTN planning. Based on this syntax and semantics, we are able to define an algorithm for HTN planning and prove it sound and complete. We also develop several definitions of expressivity for planning languages and prove that HTN planning is strictly more expressive than STRIPS- style planning according to those definitions.

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    Complexity Results for HTN Planning
    (1994) Erol, Kutluhan; Hendler, James A.; Nau, D.S.; ISR
    Most practical work on AI planning systems during the last fifteen years has been based on hierarchical task network decomposition, but until now, there has been very little analytical work on the properties of HTN planners. This paper describes how the complexity of HTN planning varies with various conditions on the task networks, and how it compares to STRIPS- style planning.