Research And Application Of Transaction Model In Workflow Management System

In recent years, workflow is one of the most rapidly developing technologies. It is the core technology to implement business automation, and also an effective technique to coordinate the complex business processes. Workflow management system (WfMS) is the tool and platform to develop and implement workflow. It is mainly used to achieve business process automation and enterprise application integration.To ensure the consistency, validity and reliability of the data of WfMS while operating, WfMS must have the ability of process transactions. Accordingly, transaction processing is one of the focuses in WfMS research. In order to describe the characteristics of transactions and solve the problem of transaction processing in workflow, people proposed many advanced transaction model, including nested transaction model, split/join transaction model, Sagas, flexible transaction model and ACTA etc. In addition, Contracts and transaction workflow, which used specially in workflow, emerged too.Sagas model was proposed by H.Garcia-Molina from Princeton University to solve the problem of long transaction. Certain resources can be released before all transactions are submitted in this model. It increased the utilization rate of resources greatly, and also strengthened the system's ability to process transactions, so it attracted widespread attention.This thesis analyzed Sagas model in detail, pointed that there were three shortages while executing accord to the flow this model defined. First, if any transaction was abnormal, all transactions submitted must be rolled back. Second, the long transaction would quit after the compensation transactions were complete, but not chose a more effective way. Third, this model had a precondition that all compensation sub-transactions were existed. In view of these three shortages, coincident point was added to preserve tasks completed as much as possible. And exception processing was added to make the model recover automatically. And compensation service was added to solve the problem that compensation sub-transaction was not existed. On this base, an improved model was created.Based on the mature technology Java and relational database, the improved model was designed in detail, the storage mode of long transaction and sub-transaction were defined, analyzed and designed the transaction manager in detail. This model was applied in Zhenjiang drainage management system. An example, the flow Contract Change in Contract Management, was cited to analyze the effect of this model, proved that the model is available and effective.