The Research Of Variable Granularity Web Service Compositions Model Based On Event Stream

In the service composition, the granularity of service effects the reusability, flexibility and efficiency of web service. The fine-grained service has the simple function, but it needs more interactions in the service composition; the coarse-grained service has rich function and independent business logic, but the internal logic may be too complex that the composited service cannot deal well with the quickly change of business needs or social environment, and it lacks of flexibility. So it needs to control the granularity of service during the service composition, in order to ensure the flexibility and efficiency of service composition.In order to control the granularity of service during the service composition, a framework of variable granularity web service compositions model based on event stream is proposed. The framework use event processing mechanism which is under the service architecture, to do event management for heterogeneous services and event processing under the service architecture. With analytic hierarchy process, we break down the web service level by level to construct the hierarchical model of variable granularity service. So the services can be replaced by its sub-processes or even sub-process'sub-process. When the service composition plan is generated, we can control the granularity of services. The main research works are as follows:First, the framework of variable granularity web service compositions is proposed, which is mainly made up of event management model for heterogeneous services, event processing under service architecture and hierarchical model of variable granularity web service. First, we model the event concept and extract the meta-data of web service, in order to construct the model of event management for heterogeneous services. Then, on the basic of event management model, we design the event processing under service architecture. At last, we use the event processing to construct the hierarchial model of variable granularity web service composition. Second, the model of event management for heterogeneous services is proposed.First, the event concept is modeled and the operation of service is seen as event. Then the meta-datas of both web service based on SAOP and RESTful web service are extracted, we use domain ontology to do semantic annotation to make them having semantic meaning. At last, this model will provide the basic data for the event processing.Third, the event processing is designed in the framework of variable granularity web service compositions. This processing includes one-way event processing and more-way event processing. The former uses the data of event management model, when the relationship of two events can meet the degree, the events and their relationship will be stored in the database; on the basic of trigger event and goal event, the latter uses the result of one-way event processing to construct the hierarchial model of variable granularity web service composition.Fourth, we construct the hierarchial model of web service composition. First, the concepts of variable granularity web service are defined. Then we use analytic hierarchy process and event processing to break down the web service, then we can get different functional services and structure nodes which connect these services, which constitute the hierarchial model of the service. When we genenrate the service composition plan, we can effectively control the granularity of service. At last, we verify the effectiveness and performability of the hierarchial service composition model.At last, we implement a prototype system, and use a typical sceen as an example to illustrate the feasibility and effectiveness of the framework. We mainly verify the event processing and constructing the hierarchial model of variable granularity web service composition, and demonstrate that the system is effective and feasible.