| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 98 === Web services define standard interfaces those provide good solutions for application integration. Quality of Service (QoS) -based web service composition (QWSC) is a methodology used widely to build new application by combining multiple web services in a flexible way. A complex application can be described as an abstract process that can be executed by invoking a number of selected web services. Users can specify the QoS constraints for the abstract process and then a service selection is performed to identify a set of available web services that fulfill not only the functionality but also the QoS constraints. However, there is a drawback for QWSC. If the user introduces severe QoS constraints for an abstract process, no feasible solution for the services selection can be identified and the service composition fails
In this research, we first propose a framework for QWSC and introduce a quick service composition mechanism. The quick service composition provides users an efficient and convenient way for creating the required application without performing the service selection algorithm. Then we introduce a relaxable QoS-based service selection (RQSS) which is a heuristic algorithm of service selection for QWSC. If no feasible solution for service selection can be identified, RQSS can find a recommended solution by relaxing some of the QoS constraints. Users can specify which QoS constraints are relaxable on their own before the service selection.
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