The recent evolution of Internet, driven by the Web services technology, is extending the role of the Web from a support of information interaction to a middleware for B2B interactions. Indeed, the Web services technology allows enterprises to outsource parts of their business processes using Web services. And it also provides the opportunity to dynamically offer new value-added services through the composition of pre-existing Web services. In spite of the growing interest in Web services, current technologies are found lacking efficient transactional support for composite Web services (CSs). In this paper, we propose a transactional approach to ensure the failure atomicity, of a CS, required by partners. We use the Accepted Termination States (ATS) property as a mean to express the required failure atomicity. Partners specify their CS, mainly its control flow, and the required ATS. Then, we use a set of transactional rules to assist designers to compose a valid CS with regards to the...