Query optimization: Mobile agents versus accuracy of the cost estimation

Abstract

Since an increasing number of diverse sources of data and information become available through World Wide Web, the field of distributed heterogeneous query processing attracts attention of the researchers. One of the main concerns is to reduce the amount of communication and the volume of data transferred in terms of query optimization where it is a real challenge to have the statistics of the resources predictable and up-to-date. Autonomy, proactivity and mobility features of mobile agents seem promising under some conditions. In this paper we are interested in the study of the efficiency of the mobile agents in relation with the approach of the cost model used during the optimization process. We present an execution model based on mobile agents. Performance evaluation shows the efficiency intervals of the execution model according to the estimation errors and the current state of the system. The major contribution of this paper is to point out the effective use of an execution model based on mobile agents in relation with the approach of the cost model and with the query type. © 2005 CRL Publishing Ltd.