Conversational Web Services: leveraging BPEL^lightfor expressing WSDL 2.0 message exchange patterns

This article uses BPELlight to capture complex message exchanges and shows how its partner model can be used to not only define bilateral message exchanges but also those conversations that involve different partner types and/or multiple instances of such partners.

Abstract

\n Message exchange patterns provide means to define the message flow\n of a service and how these messages are related in an abstract and\n reusable manner. They are an integral part of WSDL 2.0 and allow\n defining operations that have a message exchange beyond\n request-response. They reduce the impedance mismatch between\n imperative programming and message orientation while emphasizing the\n message orientated nature of Web Services. Whereas BPEL defines a\n flow between Web Service operations, BPEL light is an appropriate\n candidate to define the flow within operations since it abstracts\n from WSDL. In this article we use BPEL light to capture complex\n message exchanges. We show how its partner model can be used to not\n only define bi-lateral message exchanges but also those\n conversations that involve different partner types and/or multiple\n instances of such partners. Therefore we introduce first-class\n mechanisms to store, query and thus distinguish addressing\n information related to multiple partner instances. In addition, we\n increase reusability by allowing recursive definitions of such\n models. Thus, we enable modelling message exchange patterns that\n capture business logic in a reusable manner on an abstract level\n like for instance a request for bid scenario or a business\n transaction for purchase. Finally, we show how such patterns can be\n generically mapped to transport protocols.\n