So far our examples have all been synchronous. For example, a client invokes a session bean which performs some operation while the client waits. When the session bean completes its operation (or operations), control is passed back to the client and the client continues with the remaining operations. For some applications an asynchronous mode of operation is more appropriate, particularly in business to business applications. For example, a client may send a message requesting that an order be processed. The order processing may take some time. Once the message has been sent, the client continues with its operations. The client does not need to wait until the order has been processed. Of course the client will need to be notified in some way that the message has been received and in due course that the order has been processed. Even if the order processing is near instantaneous we may still prefer the asynchronous messaging model because we don't want to couple the client and...