Research And Implementation Of Hybrid Execution Mechanism For Composite Web Services

The good interoperability, cross-platform and loosely coupled characters have brought lots of attention and works to web service since it was proposed. As the ability of one single web service is very limited, it is usually very difficult for one single web service to properly meet the gradually changing and growing functional requirements from users. Composite Web Services which can provide value-added functions by assembling single web service according to function and logic solve this problem. And web service composition has become an important building model for applications. However, though Composite Web Services can meet the functional requirements of users, the problem of execution efficiency of Composite Web Services becomes more prominent, which is another major issue of concern to users.So it is a hot issues in recent reserches to assure the executioin efficiency of Composite Web Services in order to satisfy the requirements of users.To solve this problem, this thesis presents a hybrid execution mechanism for Composite Web Services base on Centralized Control-flow Centralized Data-flow (CCCD) execution pattern and Centralized Control-flow Distributed Data-flow (CCCD) execution pattern. The mechanism assures the execution efficiency of Composite Web Services by dynamic switching execution patterns. This thesis starts from analyzing the different execution patterns of Composite Web Services including the advantages and disadvantages of different execution patterns, and relationship between execution efficiency by execution pattern and the features of Composite Web Services like business features and environmental features. Then, this thesis presents a hybrid execution mechanism for Composite Web Services which includes Composite Web Services process instance scheduling execution layer, execution pattern selecting layer and integrated interaction layer. Next, this thesis proposes the architecture of Composite Web Services execution system to support the mechanism including the structures of execution engine and proxy service, and the protocol between them. The stucuture of execution engine includes process parse module, engine kernel and integrated interaction module. The structure of proxy service includes service registry module, protocol message module, service invocation module and persistence module. For the problem of selecting execution pattern, we present a method for execution pattern seleciton. The method includes pre-selection based on service characters and dynamic selection based on execution time.In the pre-selection we describe the decision rules and representation of the result of decision, and also an algorithm for computing the scope of deploying proxy services. In the danamic seletion, firstly, we present an evaluation model for execution pattern based execution time, and give the formulas under different strutures of Composite Web Services. Secondly, we present an algorithm for execution pattern danamic selection. Finally, we introduce the implementation details of hybrid execution mechanism supported Composite Web Services execution system and also some experiments are done to verify the effectiveness of the hybrid execution mechanism for Composite Web Services.