| With the expansion of the enterprise informationization, process of enterprise business is becoming more and more complicated, and the introduction of workflow technology to support the informationization of the business process is becoming necessary. In the trend of the globalization of economic, the reorganization and combination among enterprises is becoming popular, which result in the rise of the application for a heterogeneous and distributed environment of enterprises and the need for the workflow system which are applied in the distributed environment. With the combination of the workflow technique and Internet, the development of workflow begins a brand-new phrase.In this thesis, first, from the characteristics of the workflow management system for distributed and complicated application environment, using advanced distributed computing technology such as Web Services, .NET and so on, a frame construction for distributed and complicated application is designed. Based upon the frame construction, the concurrency control of the distributed workflow management is deeply researched. The types of the concurrency control problems, characteristics and the lack of the conventional methods are particularly expounded. In common, most of the concurrency control mechanisms of the workflow management systems regard serializability as the criterion of correctness. However, the resolution to the concurrency problem is usually ignored from the semantics point of view. Based on the analysis of the methods in existence, in this thesis, a concurrency control mechanism, which is based on workflow semantics, is proposed. This method adopts workflow semantic correctness weaker than the serializability as the correctness criterion, and guarantees the workflow semantic correctness by workflow task lock and assertion conflict table. The concurrency control mechanism based on workflow semantic correctness can solve the inconsistent problems brought by concurrent operations, and further more, it can also improve the task concurrency in order to improve the efficiency of the task.Finally, based on the theoretical research, task manager and concurrency controller in distributed workflow management system are designed and implemented. The interactive method between them is expounded, and also the transition structure and the method treat these structures. Web Services is used to wrap the concurrency controller, in order that the concurrency controller can be deployed in the Internet and can be invoked by the task managers distributed in different sites. |
