Modelling and Verification of Web Services Business Activity Protocol

WS-Business Activity specification defines two coordination protocols in order to ensure a consistent agreement on the outcome of long-running distributed applications. We use the model checker Uppaal to analyse the Business Agreement with Coordination Completion protocol type. Our analyses show that the protocol, as described in the standard specification, violates correct operation by reaching invalid states for all underlying communication media except for the perfect FIFO. Based on this result, we propose changes to the protocol. A further investigation of the modified protocol suggests that messages should be received in the same order as they are sent so that a correct protocol behaviour is preserved. Another important property of communication protocols is that all parties always reach their final states. Based on the verification with different communication models, we prove that our enhanced protocol satisfies this property for asynchronous, unreliable, order-preserving communication whereas the original protocol does not.