Research On Transaction Of Workflow Based On Web Services

Web Services is a predominant way to integrate applications both inside and outside the organization, especially it can be used as a activity in the workflow system,and Web Services composition is used as subprocess in the workflow system.The combination of Web Services and workflow will be the main solution to solve the problem of e-business, if it can provide high reliability and constitency through transaction process technology. But the flat transaction model lacks firm support for long-time-running transaction in application based on Web Services because of its strict ACID attributes.It demands relaxed transactional attributes to manage those resources of application system based on Web Services.The demand analysis of workflow transaction based on Web Services (loose coupling distributed environment) is given as a start of this thesis.And from the angel of the tier relation between Web Services composition and separated Web Service that is part of Web Services composition,a transaction model based on precontract and sematics encapsulation is presented to improve the efficiency of Web Services composition transaction process. With a concept called middle service introduced,the model uses a similar idea to reserving key resources before getting the Web Services composition transaction started.It is accomplished by the middle service tier automatically,which is not a tier for control purpose but for providing automatic invoking service.Middle service precontracts key resources and invokes Web Services that are equal to each other in sematics automatically.The compensation of separated Web Service can be greatly reduced by the service provided by middle service, and the reduction is accomplished by the middle service without any intervention of Web Services composition transaction.The transaction model based on precontract and sematics encapsulation is described in detail by this thesis, and the Web Services composition transaction process, the state conversion of middle service,the compensation of separated service and coordination frame of transaction model,and the workflow engine based on transaction model are illuminated in this thesis.Most of the realization of the model is also presented in this thesis.The transaction model based precontract and sematics encapsulation can meet requirements on long-time-running transaction of application system baesd on Web Services,and provide strong support for commercial Web Services.