An Adaptive Approach for QoS-Aware Web Service Composition Using Cultural Algorithms
Web service composition is the process of integrating existing web services. It is a prospective method to build an application system. The current approaches, however, only take service function aspect into consideration. With the rapid growth of web ser
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Abstract. Web service composition is the process of integrating existing web services. It is a prospective method to build an application system. The current approaches, however, only take service function aspect into consideration. With the rapid growth of web service applications and the abundance of service providers, the consumer is facing the inevitability of selecting the “maximum satisfied” service providers due to the dynamic nature of web services. This requirement brings us some research challenges including web service quality model, the design of web service framework monitoring service real time quality. The further challenge is to find the algorithm which can handle customized service quality parameters and has good performance to solve NPhard web services global selection problem. In this paper, we propose an adaptive web service framework using an extensible service quality model. Evolutionary algorithms are adopted to accelerate service global selection. We report on the comparison between Cultural Algorithms with Genetic Algorithms and random service selection. Keywords: cultural algorithms, genetic algorithms, web service composition, quality of service (QoS).
1 Introduction A web service pulls the web functionality from document oriented to application oriented and forms a new standard of distributed computing known as Service Oriented Architecture (SOA). Business service developers are just to assemble a set of appropriate web services to implement the business tasks. Business applications are no longer written manually. For example [1], a client requirement can be described as a workflow like a sequence diagram in UML. The workflow is composed of several sub-functional modules or abstract services. Each abstract service is associated with a web service community which contains several concrete web services with the same functionality. The process of selecting a concrete service from a web service community for an abstract service by QoS attributes is called local selection. Obviously, a task presented by the service composition can be solved by a significant number of combinations. The process of selection from the numerous combinations according to the non-functional requirement is called global selection which is a NPhard problem. Consequently, client requirements can be presented as web services M.A. Orgun and J. Thornton (Eds.): AI 2007, LNAI 4830, pp. 140–149, 2007. © Springer-Verlag Berlin Heidelberg 2007
An Adaptive Approach for QoS-Aware Web Service Composition
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global selection problem. In order to give a general approach for web service composition, we need a general quality model to present the quality of each available service. We also require the web service framework that has the functionality of realtime monitoring of the quality parameters. Moreover, we should have an efficient algorithm to globally select web services. In our work we employ evolutionary algorithms, namely Genetic Algorithms (GA) and Cultural Algorithms (CA), where the latter is used in population evolu
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