Design And Implementation Of Dynamic Web Service Composistion System Based On Qos

With the continuous improvement of web service standards and the uninterrupted maturation of enterprise-class software platform supported by web service, an increasing number of enterprises and business organizations are involved in SaaS (Software as a Service). They all packaged their business functions and components into standard web services in order to not only find partners more quickly and easily but also get potential customers with business-added purposes. However, at present, the majority of services released on the internet are simplex in structure and function, witch can not meet the needs of complex applications. Facing the various services distributed on the internet, how to effectively composite them so as to achieve seamless integration with them and create more powerful enterprise-class services processes with business goals has become an important phase. And it also becomes the key to successful application and implementation of the SOA. With the continuous expansion and commercialization of web services, customers want them to meet the expected QoS (Quality of Service) requirements and constraints. So, it is very important to provide a compositional service according to user's QoS requirements.At first, this paper studied the core technologies of web service composition and focused on the BPEL service composition method. The attributes of Web services are divided into functional properties and non-functional attributes (QoS). Then, the author extended the WSDL into a new Web Services Description Language called SWSDL (Strengthened Web Services Description Language) with non-functional attributes.Witch made the WSDL have the ability of describing the QoS attributes. According to the functional attributes of web service, the author proposed a concept of service classes. Different Web services were divided into various service classes to achieve dynamic binding of services. The author proposed a QoS-based service selection model according to non-functional properties of Web service (QoS). At last, a test scenario about travel service was given. The author completed the web service composition system with service dynamic binding and QoS supporting based on workflow technology. Tests showed that the model could meet the needs of the user's web service composition with QoS requirement.