A study of a positive fragment of path queries: Expressiveness, normal form, and minimization

Y. Wu, D. Van Gucht, M. Gyssens, J. Paredaens

    Onderzoeksoutput: Hoofdstuk in Boek/Rapport/CongresprocedureConferentiebijdrageAcademicpeer review


    We study the expressiveness of a positive fragment of path queries, denoted Path, on node-labeled trees documents. The expressiveness of Path is studied from two angles. First, we establish that Path is equivalent in expressive power to a particular sub-fragment as well as to the class of tree queries, a sub-class of the first-order conjunctive queries defined over label, parent-child, and child-parent predicates. The translation algorithm from tree queries to Path yields a normal form for Path queries. Using this normal form, we can decompose a Path query into sub-queries that can be expressed in a very small sub-fragment of Path for which efficient evaluation strategies are available. Second, we characterize the expressiveness of Path in terms of its ability to resolve nodes in a document. This result is used to show that each tree query can be translated to a unique, equivalent, and minimal tree query. The combination of these results yields an effective strategy to evaluate a large class of path queries on documents.
    Originele taal-2Engels
    TitelDataspace: The Final Frontier (26th British National Conference on Databases, BNCOD 26, Birmingham, UK, July 7-9, 2009. Proceedings)
    RedacteurenA.P. Sexton
    Plaats van productieBerlin
    ISBN van geprinte versie978-3-642-02842-7
    StatusGepubliceerd - 2009

    Publicatie series

    NaamLecture Notes in Computer Science
    ISSN van geprinte versie0302-9743


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