Web services are defined independently of any execution context. Due to their inherent autonomy and heterogeneity, it is difficult to examine the behaviour of composite services, especially in case of failures. This paper is interested in ensuring composite services reliability. Reliable composition is defined as a composition where all instance executions are correct from a transactional and business point of view. In this paper, the authors propose a transactional approach for ensuring reliable Web service compositions. The approach integrates the expressivity power of workflow models and the reliability of Advanced Transactional Models (ATM). This method offers flexibility for designers to specify their requirements in terms of control structure, using workflow patterns, and execution correctness. Contrary to ATM, the authors start from the designers’ specifications to define the appropriate transactional mechanisms that ensure correct executions according to their requirements.

Control and data dependencies are important information in business processes that supports process modeling, analysis, and execution. However, sequencing constraints, which are prescribed by control structures, obfuscate the true sources of dependencies. In addition, most work improperly equalizes sequencing constraint and control dependency, and regards data dependencies as a flow of data processing relying on sequencing constraints.In this paper, business activities are described with a semantic description that defines precondition, effect, input, and output. Based on which we specify what control and data dependencies are. Control dependencies are related to the precondition and the effect. Mandatory data dependencies are related to the input and the output, while optional data dependencies are derived from possible conditions on business activities. All control and data dependencies are optimized into a minimal dependency graph which captures essential dependencies to be preserved. A sequencing constraint is possibly due to control and/or data dependencies. A clear view on the relation and the difference between sequencing constraint and control/data dependency is crucial to better support process modeling, analysis, and execution.

Reliability is one of the main challenge that encounter Web servicescompositions. Due to the inherent autonomy and heterogeneity of Webservices it is difficult to predict the behavior of the overallcomposite service.Current related technologies are unable to resolve this problemefficiently. These technologies rely on two existing strongapproa-ches: transactional processing and workflow systems. In onehand transactional processing ensures reliability. However, they aretoo rigid to support process based applications like composite Webservices. On the other hand, workflow systems focus mainly oncoordination and organizational aspects and ignore reliabilityissues.In this paper we propose a new solution that combines the businessprocess adequacy of workflow systems and the reliability oftransactional processing. We introduce the concept of transactionalpatterns to ensure reliable composite services. A transactionalpattern can be seen as a convergence concept between workflowpatterns and advanced transactional models. We show how we use it todefine composite services and how we ensure their reliabilityaccording to the designers specific needs.

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 specified ATS.