Query Optimization over Web Services

Abstract

Web services are becoming a standard method of sharing data and functionality among loosely-coupled systems. We propose a general-purpose Web Service Management System (WSMS) that enables querying multiple web services in a transparent and integrated fashion. In this paper, we consider the problem of query optimization inside a WSMS for Select-Project-Join queries spanning multiple web services. Our main result is an algorithm for optimally arranging the web services in a query into a pipelined execution plan that minimizes the total running time of the query. We also give an algorithm for determining the optimal granularity of data ``chunks'' to be used for each web service call. Analytical comparisons demonstrate that our algorithms can lead to significant performance improvement over more straightforward techniques.