Designing Atomic Business Functions with Distributed Control

The subject matter of this paper is concerned with the coordination of message-based interactions within the context of business-to-business integration (B2Bi) that autonomous organizations - business partners - need to do in order to automate their business functions such as travel booking, order fulfilment and so forth. B2Bi solutions offered by vendors fall into two broad categories: hub-and-spoke (interaction between partners takes place through a central hub that acts as an intermediary), and peer-to-peer (interaction takes place directly between partners). An important coordination problem in B2Bi that needs addressing is how to ensure that business interactions between partners terminate in a consistent manner even in the presence of application level exceptions and software, hardware and network related problems commonly encountered in distributed systems. Solutions that have been developed so far and incorporated in SOA middleware are essentially based on OASIS WS-TX set of transaction standards, namely WS-coordination, WS-Atomic Transaction and WS-Business Activity. WS-TX based solutions require a central activity coordinator. The paper argues that although these solutions are quite suitable within a hub- and spoke B2Bi architecture, they sit awkwardly in peer-to-peer B2Bi settings, where a distributed approach, not requiring a central coordinator is more suitable. The paper develops such an approach, it focuses on the choreography of the business function and describes how to make the choreography atomic, ensuring consistent termination in the presence of application level exceptions and failures.