A service-oriented workflow language for robust interacting applications

In a service-oriented world, a long-running business process can be implemented as a set of stateful services that represent the individual but coordinated steps that make up the overall business activity. These service-based business processes can then be combined to form loosely-coupled distributed applications where the participants interact by calling on each other's services. A key concern is to ensure that these interacting service-based processes work correctly in all cases, including maintaining consistency of both their stored data and the status of the joint activities. We propose a new model and notation for expressing such business processes which helps the designer avoid many common sources of errors, including inconsistency. Unlike most existing orchestration or workflow(a) languages used for expressing business processes, we do not separate the normal case from exceptional activity, nor do we treat exceptional activity as a form of failure that requires compensation. Our model has been demonstrated by developing prototype systems.