Streaming XPath Subquery Evaluation.
Feng Peng and Sudarshan S. Chawathe.
Technical Report CS-TR-4376 (UMIACS-TR-2002-56). Computer Science Department, University of Maryland, College Park, Maryland 20742. January 2004.
[ paper | citation ]

We describe a method for the streaming evaluation of XPath queries that have subqueries in pred- icates. Our method rewrites XPath queries into a set of predicate-free labeled linear-form expressions (LFEs). These LFEs are used to generate a push-down transducer that enables efficient management of a buffer and hierarchical index at runtime. To the best of our knowledge, our method is the first to support XPath subqueries in a streaming environment. Our method also provides optimal buffering, minimum-latency output, and optimal predicate evaluation. The method has been fully implemented and publicly released in the XSQ system. We present an experimental study of XSQ and related systems on both real-life and synthetic datasets, and investigate how subqueries and other features affect the performance of these systems.

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