Research Of Web Services Composition Based On QoS And Semantic Web

Web services are self-contained, modularized applications on the web, which can be described, published, located, and invoked over internet. So applications' functions can be extended and software can be dynamically provided. With the continuous development of e-commerce and the growing scale of cross-enterprise applications, business processes become more and more complex. However, functions provided by a single service are still so limited that they cannot satisfy complex business processes. The need for composing existing services with different functions according to certain logic of business processes into more complex services has become more urgent.Web service composition provides an open, standards-based approach for connecting web services together to create higher-level business processes for exploring the potential of Web services to provide more and more powerful services. The current web service composition is still involved with manual or semi-automatic combination methods.With more and more studies on the web service, semantic web services can well solve the problem by realizing intelligent web services. Semantic web services are the integration of web services and semantic with the goal that it can be understood by the machine through the web service description to support the service discovery, selection, and composition automatically. With the wide applications of Web services, Web services' number is increasing day by day, and there are many services with same function provided by the internet. How to select the best services that can meet the requirements from many services which have the same function has become an urgent problem. Therefore, the research of web service based on Semantic and Qos will promote the web service composition's automation, reduce the burden of service developer, and improve query results'satisfaction and service modules reusability.There may be a group of paths which all construct the composition, which means a service need some services'output to perform its operation. That is multi-service problem. Additionally, vertex in DAG probably have more elements, and it may lead to some problems which are called multi-input problems. Therefore, this thesis uses an AND/OR graph to present the composed services paths, which can express data flow relationships more clearly in the process of service composition and can solve the problems of multi-service and multi-input. In a comprehensive analysis of several existing services composition model, a Web Services composition framework is proposed based on decomposable production system architecture. After presenting Web Services registered as a set of rules and composition process of Web Services as an Input/Output Illation AND/OR graph, seeking the optimal composition is to find out optimized solution graph from the AND/OR graph. Heuristic Searching Tactic is discussed in the end. By the analysis and comparison, all possible composition of services can be presented and the best can be found out efficiently in the framework.On the basis of analyzing the existing web services, an extended UDDI framework based on semantic and Qos is proposed in this thesis by improving the existing service registration and discovery mechanism. In this framework, service providers can define non-functional and semantic properties on related services qualities for each service and register them to the UDDI and discover web services via semantic deduction. This framework adds some extended modules, such as OWL-S/UDDI matchmaker, by preserving the current web service standards to realize the perfect combination of old and new technologies. The framework adds the management module for the web services association, which adopts services association index mechanism to enhance the efficiency of service discovery, composition service discovery and matching. By extending the describing function of OWL-S for the service quality attributes, the framework adds the Web service's QoS support and QoS management module to calculate the Qos for the different users' needs weight, monitor the operation of the services, deal with user feedback on service quality and update Qos information timely.Finally, this thesis introduces the tools and the building process of experimental environment that realizes the framework which extends semantic and Qos functions, and gives some simulation experiments pictures based on semantic composition.