Efficient Rewriting of XPath Queries Using Query Set Specifications

Bogdan Cautis, Alin Deutsch, Nicola Onose and Vasilis Vassalos
March 19, 2009

We study the problem of querying XML data sources that accept only a limited set of queries, such as sources accessible by Web services which can implement very large (potentially infinite) families of XPath queries. To compactly specify such families of queries we adopt the Query Set Specifications~\cite{PetropoulosDP03}, a formalism close to context-free grammars. We say that query $Q$ is {\em expressible} by the specification \calP\ if it is equivalent to some expansion of \calP. $Q$ is {\em supported} by \calP\ if it has an equivalent rewriting using some finite set of \calP's expansions. We study the complexity of expressibility and support and identify large classes of XPath queries for which there are efficient (PTIME) algorithms. Our study considers both the case in which the XML nodes in the results of the queries lose their original identity and the one in which the source exposes persistent node ids.

How to view this document

The authors of these documents have submitted their reports to this technical report series for the purpose of non-commercial dissemination of scientific work. The reports are copyrighted by the authors, and their existence in electronic format does not imply that the authors have relinquished any rights. You may copy a report for scholarly, non-commercial purposes, such as research or instruction, provided that you agree to respect the author's copyright. For information concerning the use of this document for other than research or instructional purposes, contact the authors. Other information concerning this technical report series can be obtained from the Computer Science and Engineering Department at the University of California at San Diego, techreports@cs.ucsd.edu.

[ Search ]

This server operates at UCSD Computer Science and Engineering.
Send email to webmaster@cs.ucsd.edu