Quality of service is one of the most important factors in the design and composition of web services. In recent years number of web services has increased dramatically, resulting in similar services with similar functionality are available. So the quality of the services is a criteria which causes difference among similar functionality services. In addition, users considering their needs may require a combination of these services. Therefore, choosing the optimal composite web services has become a challenging and time consuming problem. In this paper, two aspects of this problem have been studied. First, the problem has been converted to a single-objective problem. In this state, to increase the speed, accuracy and reliability, we apply a combination of genetic algorithm, fuzzy logic and support services. Then the problem has been changed to a multi-objective problem and solved by multi-objective evolutionary algorithm, such as Non-dominated Sorting Genetic Algorithm (NSGA-II). Experiment result shows that the improved algorithm increases the speed when a large number of web services are available.
Web service composition; Genetic Algorithm; Evolutionary Algorithms; Optimization