As we've seen in Chapter 1, with the evolution of ever cheaper and more powerful computers, the ability to run a system with applications distributed over a number of machines has turned from a pipe dream into a reality. Correspondingly, the need for system users to access the system from a single machine has developed into each user having his own computer and accessing the required application over a network.
However, as you distribute the processing and the data in a system, you then have to start worrying about how the systems are connected together. In many instances, the connection may not be permanent. You may have to dial-up or dock your machine in order to connect and exchange information. It is these types of distributed systems where message queuing can provide great advantages.
A disconnected user can perform local tasks with their application. That application can queue messages for delivery to other application until the computer is connected to the network again. When the computer is connected to the network, the queued messages can be sent, and messages bound for this computer can be received and processed automatically. This support for distributed applications makes message queuing technology an important technology in creating tomorrow's business applications.