Several approaches to semantic Web services, including OWL-S, SWSF, and WSMO, have been proposed in the literature with the aim to enable automation of various tasks related to Web services, including discovery, contracting, enactment, monitoring, and mediation. The ability to specify processes and to reason about them is central to these initiatives. In this paper we analyze the WSMO choreography model, which is based on Abstract State Machines (ASMs). and propose a methodology for generating WSMO choreography from visual specifications. We point out the limitations of the current WSMO model and propose a faithful extension that is based on Concurrent Transaction Logic (CTR). The advantage of a CTR-based model is that it uniformly captures a number of aspects that previously required separate mechanisms or were not captured at all. These include process specification, contracting for services, service enactment, and reasoning.
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