Message flow control

High level communication by means of the exchange of messages between different organizations or organizational units is studied. The concepts of business transaction and business transaction protocol are discussed. Message exchanges are controlled by a message handler that enforces a transaction protocol. The design and implementation of a generic message handler is described. The design is independent of a specific application. It offers a flexible implementation of protocols: dedicated subprocesses handle each message type. Changes in a protocol can easily be accommodated by adapting the subprocesses. A prototype has been written in the executable specification language ExSpect. The protocols can be validated by simulating the message exchange for a number of cases. As an application of the prototype, a party in a logistic chain using EDI is described