Abstract

Web services are becoming a standard method of sharing data and functionality among loosely-coupled systems. We propose a general-purpose Service Query Management frame (SQM) that enables querying multiple web services in a transparent and integrated fashion. This paper tackles a first basic SQM problem: query optimization for Select-Project-Join queries spanning multiple web services. Our main result is an algorithm for arranging a query's web service calls into a pipelined execution plan that optimally exploits parallelism among web services to minimize the query's total running time. Experiments with an initial prototype indicate that our algorithms can lead to significant performance improvement over more straight forward techniques.

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