The Design And Implementation Of Self-Adaptive Service Composition System Based On Context Awareness

Web service compositions run in complex and changing environment where dif-ferent context events can arise to affect the execution of services. In order not to make service execution affected by context events, context-aware service composition be-comes one of the major research trends. Service providers can develop context-aware services which can adapt their behaviors dynamically to execution contexts. However, it burdens service providers because they have to keep in mind different execution con-texts where their services could be used.In order to provide context-aware services and free service providers from con-text handling, this paper focuses on context awareness. We design and implement a self-adaptive and context-aware service composition system. It frees service providers from context handling which in turn becomes a task of our system. It provides service registration interface for service providers to register their services into our system. It can composite services according to service requests using HTN planning method and give service consumers context-aware services. Our system can adapt to changing execution contexts and make adjustments according to context events and user-defined personalized self-adaption policies.In order to accomplish the above research objectives, the main research work in this paper is as follows:1. Web service description language OWL-S is studied comprehensively and thor-oughly. Then, this paper analyzes web service composition methods and com-pares their advantages and disadvantages. A popular HTN planning engine JSHOP2 is introduced. We systematically and comprehensively analyze related research work on self-adaptation and context-awareness including context defi-nition, context categorization and context-aware framework.2. In order to provide self-adaptation in the execution environment, we design a self-adaption policy language for service consumers to make their personalized policies. Our system makes adjustments according to their policies.3. In order to handle complex and changing execution contexts, we give our def-inition of context and categorize it into three categories. Then, we extend the OWL-S model to support context tags. Finally, we design a self-adaptive and context-aware framework which can monitor contexts in the execution environ-ment and make adjustments according to context events and user-defined self-adaption policies.4. Based on the above research work, a self-adaptive and context-aware service composition system is designed and implemented. We verify the functionality of our system using an example-online ticket booking.