Research On Transactional Workflows In Distributed And Heterogeneous Environment

Workflow management systems are used to coordinate and automate business processes. Since process instances often access shared persistent data and run concurrently, they are subject to transactional properties. In order to enhance the reliability of WfMS and to ensure the correctness of complex business processes in distributed and heterogeneous environment, it is important to guarantee those transactional properties. But transactions in workflow applications are different from traditional flat ones. They are typically long running and with coarse-grained operations. And the recovery guarantees of different activities are dissimilar. Furthermore, semantics of the applications are rich. For example, a workflow instance may terminate successfully in different ways. So even advanced transaction models and methods are not suitable for workflow applications.In the early 1990's, the term transactional workflow was introduced to clearly recognize the relevance of transactions to workflows. The development of transactional workflow technology is of great importance for pushing workflow technology into practice. Transactional workflow technology has been a research focus of both transaction management and workflow areas.To ensure the correnctness of transactional workflow, both define-time and run-time factors are to be considered. Firstly, in order to precisely describe features of transactional workflow, a proper theoretical model must be built. Secondly, the wellformness of the definition of transactional workflow should be checked, since mismatch of recovery policies of different transactional activities may lead to violation of transactional properties. Thirdly, the execution of a transactional workflow instance must bring the system from a consistent state to another consistent state, and it must ensure the semantic property. Therefore, concurrency control and failure recovery mechanism should be provided for the run-time correctness.To solve existing problems, we have made comprehensive research work on the following issues in this dissertation: the transactional workflow model, well-formness validation of transactional workflow definition, concurrency scheduling, failure recovery and the implementation framework of transactional WfMS. We use well-defined semantics to describe the characteristics of transactional workflows. And we propose relevant algorithms and mechanisms to enhance the reliability and correctness of WfMSs. The research work also extends to Web Services based transactional workflow environment to meet the transactional requirements of long running complex business processes in distributed and heterogeneous environment. The contributions of this dissertation include:(1) We have made comprehensive research work on transaction processing...