Research On Key Technologies For Dynamic Web Services Composition

By using web services, there will be a method, which is possible and convenient to be executed, to implement the integration and dynamic collaboration of enterprise application. By applying web services and through the loose integration of the applications, the applications of different enterprises can be organized efficiently to implement the information sharing and business collaboration, and can realize the automation of business process through cross-enterprise workflow system. As the application systems of enterprises have becoming more and more complex, and because of the complexity and the levity of Internet environment, currently the business integration system of cross-enterprises web service still has some major problems as follows:1) The development and deploying of web service have not yet been completely separated, the lack of enough agility limits their growing; the web service and server are always static bound, it can not support the dynamic deploying of web service in distributing environment, and can not dynamically bind the web service on available sever to run.2) In the combination process of cross-enterprise web service, there is a lack of efficient mechanism, which can ensure the dynamic detection of a service with high performance vs. price ratio when circulating.3) Composition process of cross-enterprise web service is lack of dynamic description; it cannot make timely reaction to the dynamical changing operation environment, so the control and collaboration cannot be efficiently processed.4) The static binding of web service and needed source limits the sharing of cross-enterprise resources, can not supply safe and efficient mechanism, according to the actual run environment of web service to realize cross-enterprise resource sharing.This paper analyzes the key technologies for dynamic web service composition and the existing difficulties, integrates the cross-enterprise workflow process model and process controlling, extends the web service description and separates the development and deployment of web services under service-oriented architecture. During the dynamic composition process of workflow-oriented web servicies, theservice is dynamically deployed and bound according to the actual application requirements. A flexible fault tolerance mechanism is also provided to ensure the normally running of dynamically deployed web services. At the same time, this paper builds a model of dynamic virtual enterprise, which is under service-oriented architecture and based on dynamic composition of web services, and discusses the safely sharing of resources among the cross-enterprise web services.Basically, the main achievements of this paper focus on the following aspects:1) Bring forward the extended model for web service descriptionIn order to support the fully separation of development and deployment of web services, and also support the dynamically deploying and stable running of the web services during the dynamic composition of the web services, this paper extends the web service description by adding the information of resource requirement, installation configuration, and service related policies (such as safely accessing policies, fault tolerance policies and trusted right delegation policies, etc.).2) Present a workflow-oriented dynamic web service composition modelIn order to support the coordination and controlling of the dynamic composition of web services, this paper discusses how to use dynamic workflow model to integrate web service composition process with workflow process model and then build the workflow-oriented composite web service. Through using service evaluation function in the execution process of the composite web service, and also according to the business logic and rules between the tasks that defined in the workflow process model, it can implement the dynamic binding and execution of the workflow tasks.3) Put forward a policy-driven and multi-agent based fault tolerance modelIn order to support the efficient fault handling by the host server for the fault occurrence of the web service during the dynamic composition of web services, this paper extends the web service description with fault tolerance policies and introduces the multi-agent system. Through the interaction and cooperation of the multi agents, the system can monitor the occurrence of faults and deal with the faults efficiently in the execution process of the webservice with the direction of fault tolerance policies.4) Present a virtual enterprise model based on the dynamic composition of web servicesIn order to support the dynamically integration and cooperation of cross-enterprise information application systems, this paper utilizes the web services to encapsulate them and builds a virtual enterprise model based on dynamic composition of web services. It supports the dynamic joining and exiting of the enterprise members in the running process of virtual enterprise. To ensure the stable running of virtual enterprise, this paper introduces the trusted right delegation mechanism to ensure the efficient and safe utilization of the web service resources.