Distributed query execution adaptation

This paper presents a strategy for adapting the execution coordination process in mediation systems. This strategy was designed for distributed data environments, typical of virtual organizations, where the vertical and horizontal fragmentation is not disjoint. The principle of the adaptation strategy is to dynamically choose the sources participating in the execution of a query using a collaborative model based on the LINDA tuple space. This model proves to be useful to coordinate asynchronous interaction between sources and to adapt naturally the query execution when there are unstable states of physical resources, low rate responses or failure of sources.