Abstract: As a new parallel computing model,Web Service,which has the advantages of platform independence,loose coupling and autonomy,has great potential and demand in service industry involved with complex business processes．Considering the limitations and characteristics of Web Service environment,traditional transaction model cannot be suited．This paper departed from the architecture of the Web service transaction systems,analyzed the characteristics of Web Service and Web Service transactional applications in an open Web environment,and finally proposed a nested mo-del of Web Service transaction combining alternative and compensation．We also illustrated the structure and processing of Web Service transaction combining with alternatives and compensation mechanism and presented a formal representation of this model．

Key words: Web service,Web service transaction,Transaction model