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  • Finding irredundant contained rewritings of tree pattern queries using views

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    Author(s)
    Wang, Junhu
    Wang, Kewen
    Li, Jiuyong
    Griffith University Author(s)
    Wang, Kewen
    Wang, John
    Year published
    2009
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    Abstract
    Contained rewriting and maximal contained rewriting of tree pattern queries using views have been studied recently for the class of tree patterns involving /, //, and []. Given query Q and view V, it has been shown that a contained rewriting of Q using V can be obtained by finding a useful embedding of Q in V. However, for the same Q and V, there may be many useful embeddings and thus many contained rewritings. Some of the useful embeddings may be redundant in that the rewritings obtained from them are contained in those obtained from other useful embeddings. Redundant useful embeddings are useless and they waste computational ...
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    Contained rewriting and maximal contained rewriting of tree pattern queries using views have been studied recently for the class of tree patterns involving /, //, and []. Given query Q and view V, it has been shown that a contained rewriting of Q using V can be obtained by finding a useful embedding of Q in V. However, for the same Q and V, there may be many useful embeddings and thus many contained rewritings. Some of the useful embeddings may be redundant in that the rewritings obtained from them are contained in those obtained from other useful embeddings. Redundant useful embeddings are useless and they waste computational resource. Thus it becomes important to identify and remove them. In this paper, we show that the criteria for identifying redundant useful embeddings given in a previous work are neither sufficient nor necessary. We then present some useful observations on the containment relationship of rewritings, and based on which, a heuristic algorithm for removing redundant useful embeddings. We demonstrate the efficiency of our algorithm using examples.
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    Journal Title
    Lecture Notes in Computer science
    Volume
    5446
    DOI
    https://doi.org/10.1007/978-3-642-00672-2_12
    Copyright Statement
    © 2009 Springer Berlin / Heidelberg. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. The original publication is available at www.springerlink.com
    Subject
    Database systems
    Publication URI
    http://hdl.handle.net/10072/30609
    Collection
    • Journal articles

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