On the Query Evaluation in Document DBs
In this paper, we study the query evaluation in document databases. First, we show that a query represented in an XML language can be generally considered as a la beled tree, and the evaluation of such a query is in fact a tree embedding problem. Then, we propose a strategy to solve this problem, based on dynamic programming. For the ordered tree embedding, the proposed algorithm needs only O(|T|(|P|) time and O(|T|(|P|) space, where |T| and |P| stands for the numbers of the nodes in the target tree T and the pattern tree P, respectively. This computational complexity is better than any existing method on this issue. In addition, how to adapt this method to the general tree embedding is also discussed.
KeywordsParse Tree Virtual Node Query Evaluation Conjunctive Query Label Tree
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