| The fast growing E-Business requires more and more different E-business systems to be connected to each other. With the traditional Web technology, one has to develop a specific interface for a specific E-business system to connect to another specific E-business system. It is very time consuming and very costly. It can not meet the business demand in this fast changing and highly competitive E-business environment. Therefore, Web service composition technology is being developed to provide a solution to coordinate and organize multi-services and to construct a new service or application system according to an assigned order.In the recent years, people have done a great deal of research work in service quality evaluation area. It is still in the early stage regarding e-service quality. While the implementation of the function of Web service composition has been mostly focused on in the researches, the quality of service (QoS) has often been ignored. There are still some major problems in QoS, which are described as below:The traditional service quality evaluation model which applied into the service under face to face cannot meet the requirement in e-service. Current researches in e-service quality area lack of supporting to Web service.The commonly used Web service description language WSDL is a Web service interface definition language. With XML format, Web services are described as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. As a setback, WSDL does not provide Web service QoS property description.UDDI (Universal Description, Discovery and Integration) provides a unified and platform-independent Web service registry and request function. Through the UDDI, consumers can find the services which meet their functional requirements by using key words. However, UDDI does not provide non-functional QoS information. Under some circumstances, users may have difficulties to decide which service is suitable for them.Current QoS researches only focus on some of QoS attributes and local implementations. It does not provide overall QoS framework in Web service composition process.In the Web service composition process, atomic service selection optimization normally uses a linear analysis method, which has certain limitations.With the analysis of the key technologies used in the dynamic Web service composition and in a real E-business application case, a practical solution and a framework for QoS-based Web services composition technology are proposed. The main contributions of this thesis to Web composition technology include following areas:Seven dimensions quality evaluation model which is fit to Web service has been proposed. In this model different description of traditional elements -tangibles, reliability, responsiveness, assurance, empathy are given and new conception, couple level and information cost, is introduced.To establish a unified Web service QoS property description for both Web service publisheres and Web service consumeres, QoS properties are analyzed. Based on the uniqueness of Web service composition properties, a formal description is given to a Web service composition QoS model, which established a QoS ontology model.A WSDL-Q conceptual model is proposed, which improves current Web service description structure. It is proposed to insert QoS information to WSDL-Q description, which will help the search for QoS based Web services.A QoS-based EUDDI (Enhanced UDDI) architecture is proposed. QoS management mechanism is added into the traditional UDDI, which makes it capable of separating different QoS with the same service function thus make the Web service more efficient and more accurate.A special QoS-based Web Service Composition Framework, QWSCF is proposed, which introduces a unique concept of QoS-based Web Service Composition.
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