Counting Twig Matches in a Tree

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Counting Twig Matches in a Tree
We describe efficient algorithms for accurately estimating the number of matches of a small node-labeled tree, i.e., a twig, in a large node-labeled tree, using a summary data structure. This problem is of interest for queries on XML and other hierarchical data, to provide query feedback and for costbased query optimization. Our summary data structure scalably representsapproximate frequencyinformation about twiglets (i.e., small twigs) in the data tree. Given a twig query, the number of matches is estimated by creating a set of query twiglets, and combining two complementary approaches: Set Hashing, used to estimate the number of matches of each query twiglet, and Maximal Overlap, used to combine the query twiglet estimates into an estimate for the twig query. We proposeseveral estimation algorithms that apply these approaches on query twiglets formed using variations on different twiglet decomposition techniques. We present an extensive experimental evaluation using several real XML...
Zhiyuan Chen, H. V. Jagadish, Flip Korn, Nick Koud
Added 01 Nov 2009
Updated 01 Nov 2009
Type Conference
Year 2001
Where ICDE
Authors Zhiyuan Chen, H. V. Jagadish, Flip Korn, Nick Koudas, S. Muthukrishnan, Raymond T. Ng, Divesh Srivastava
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