An internetware application is composed by existing individual services, while transaction processing is a key mechanism to make the composition reliable. The existing research of transactional composite service (TCS) depends on the analysis to composition structure and exception handling mechanism in order to guarantee the relaxed atomicity. However, this approach cannot handle some application-specific requirements and causes lots of unnecessary failure recoveries or even aborts. In this paper, we propose a relaxed transaction model, including system mode, relaxed atomicity criterion, static checking algorithm and dynamic enforcement algorithm. Users are able to define different relaxed atomicity constraint for different TCS according to application-specific require- ments, including acceptable configurations and the preference order. The checking algo- rithm determines whether the constraint can be guaranteed to be satisfied. The enforce- ment algorithm monitors the execution and performs transaction management work ac- cording to the constraint. Compared to the existing work, our approach can handle com- plex application requirements, avoid unnecessary failure recoveries and perform the transaction management work automatically. The existing research of transactional composite service (TCS) depends on the analysis to composition structure and exception handling mechanism in order to guarantee the relaxed atomicity. However, this approach can not handle some application-specific requirements and causes lots of unnecessary failure recoveries or even aborts. In this paper, we propose a relaxed transaction model, including system mode, relaxed atomic criterion, static checking algorithm and dynamic enforcement algorithm . Users are able to define different relaxed atomicity constraints for different TCS according to application-specific require- ments, including acceptable configurations and the preference order. The checking algo- rithm determines whether the constraint can be guaranteed to be satisfied. The enforce ment algorithm monitors the execution and pe Compared to the existing work, our approach can handle com- plex application requirements, avoid unnecessary failure recoveries and perform the transaction management work automatically.