Extending BPELlight for Expressing Multi-Partner Message Exchange Patterns

Message exchange patterns provide means to define the message flow of a service and how these messages are related in an abstract and reusable manner. They are an integral part of WSDL 2.0 and allow defining operations that have a message exchange beyond request response. They reduce the impedance mismatch between imperative programming and message orientation while emphasizing the message orientated nature of Web services. Whereas BPEL defines a flow between Web service operations, BPELlight is an appropriate candidate to define the flow within operations since it abstracts from WSDL. In this paper we extended BPELlight to facilitate capturing complex multi-lateral message exchanges. We refine the partner model and relax the definition of a conversation to enable modelling conversations that involve different partner types. We also extend the language with a first-class construct that enables storing, querying and thus distinguishing addressing information related to multiple partner instances. This way we enable modelling message exchange patterns that capture business logic in a reusable manner on an abstract level like for instance a request for bid scenario or a business transaction for purchase.