The integration design is implicit, really only existing in the mind of the designer. The implementation is built into the applications themselves. If a message broker is used, applications send and receive messages from the broker only. The need for a broker becomes apparent when for one reason or another there are lots of different routing and transformation combinations. In any event, as the rules and conditions for routing messages get more and more complex and even difficult to remember it becomes more and more inadvisable to bury those rules and conditions within multiple applications, making maintenance a nightmare.
Brokers support information flow the directed flow of information between applications.
Looked at from the perspective of business process, information flow is applicable when the information alone is sufficient to significantly improve operations. Whereas some tasks are adequately supported by information alone, other tasks involve teamwork and unique conditions. A lone dancer needs only to hear the music. Perhaps the procedures are so complex, or the order volume so high, that it is not uncommon to lose an order or forget to return shipment information. Workflow is meant to help in such situations.