Generating Scenarios from Web Service Choreography

Web services choreography describes the global model of service interactions among a set of participants. In order to achieve a common business goal, the protocols for interactions must be correct. Experiences show that it is difficult to check choreography manually, even it is not very complex. A scenario describes a sequence of interactions among the collaborative participants, that is useful for judging if a choreography satisfies the intended business requirements. However, building the scenarios for a choreography is not easy even if with a supporting tool, such as Pi4SOA. In this paper, we propose an approach, and a set of algorithms, for generating the scenarios of a choreography automatically. For the fundamental study, a small choreography language CDL capturing the core features of Web services choreography description language WS-CDL is developed, with its formal syntax and trace semantics. The scenarios are defined basing on the choreography model, and the algorithms for generating scenarios from CDL is presented. We use a purchase order example to show how service choreography can be specified in CDL, and how the scenarios are generated and used to check the choreography. A prototype tool has been developed on Pi4SOA which shows the approach is both viable and effective.