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Transforming XPath Expressions into Relational Algebra Expressions With Kleene Closure

Authors:
Yangjun Chen

Keywords: XML, XPath, Query Processing, XPath transformation

Abstract:
In the problem of translating XPath expressions into SQL queries, the most challenging part is to find a way to minimize the use of least fixpoint (LFP) operators when a DTD graph contains cycles. In this paper, we address this issue and present a new algorithm to do the task based on the recognition of a kind of DTD graphs, which can be reduced to a single node by contracting nodes into their parents one by one. For this kind of DTD graphs, not only the corresponding relational algebra expressions can be efficiently generated, but the use of LFP operators can also be minimized. For those DTD graphs that are not reducible, we devise a different algorithm which is less efficient than the algorithm for reducible graphs, but more efficient than any existing method.

Pages: 114 to 121

Copyright: Copyright (c) IARIA, 2011

Publication date: January 23, 2011

Published in: conference

ISSN: 2308-4332

ISBN: 978-1-61208-115-1

Location: St. Maarten, The Netherlands Antilles

Dates: from January 23, 2011 to January 28, 2011