a qos-based selection approach of autonomic grid services
The Web service composition (WSC) is the process of building an instance of an abstract workflow by combining appropriate Web services that satisfies given QoS requirements. In general, QoS requirements consists of a number of constraints. The selection process requires global optimization and can be formalized as a mixed integer linear programming problem which cannot be solved in polynomial time. However, since the number of submitted workflows is large and the QoS is highly dynamic, the fast selection of composite Web Services is particularly important. In this paper, we present a QoS broker-based framework for Web services execution in autonomic grid environments. The main goal of the framework is to support the broker in selecting Web services based on the required QoS. To achieve this goal, we propose a novel approach: since successive composed Web services requests can have the same task to Web service assignment, we address the Multiple Instance WSC (MI-WSC) problem optimizing simultaneously the set of requests which will be submitted to the system in the successive time interval instead of independently computing a solution for each incoming request. Experimental results show that the proposed algorithm has better performance with respect to existing techniques. Moreover, the qualities of the selected composite Web services are not significantly different from the optimal ones.
grid heuristics quality of service web service selection autonomic systems