Describing Component Collaboration Using Goal Sequences

Services are normally not performed by a single component, but result from the collaboration of several distributed components. Their precise specification and validation require complex models, where the intention of the service is easily lost in the detail. This paper exploits the concept of service goals that was earlier introduced to simplify service modeling. It describes the semantics of service goals, how to specify and how to use them. We show that so-called goal sequences can provide a designer-friendly, high-level description of the intention of the service, while maintaining simplicity, reusability and flexibility when composing from elementary services. By way of examples, we illustrate the difference between goal sequences and behavior descriptions. Finally we discuss issues related to the validation of goal sequences and their use at design time and runtime, for example in connection with service discovery.