A hybrid genetic algorithm for the optimal constrained webudservice selection problem in web service compositionud

摘要

Web service composition is an important problem in web service based systems. It is about how to build a newudvalue-added web service using existing web services. A webudservice may have many implementations, all of which have theudsame functionality, but may have different QoS values. Thus,uda significant research problem in web service composition isudhow to select a web service implementation for each of the web services such that the composite web service gives the best overall performance. This is so-called optimal web service selection problem. There may be mutual constraints between some web service implementations. Sometimes when an implementation is selected for one web service, a particular implementation for another web service must be selected. This is so called dependency constraint. Sometimes when an implementation for one web service is selected, a set of implementations for another webudservice must be excluded in the web service composition. This is so called conflict constraint. Thus, the optimal web service selection is a typical constrained ombinatorial optimization problem from the computational point of view. This paper proposes a new hybrid genetic algorithm for the optimal web service selection problem. The hybrid genetic algorithm has been implemented and evaluated. The evaluation results have shown that the hybrid genetic algorithm outperforms other two existing genetic algorithms when the number of web servicesudand the number of constraints are large.