You may also like: Comparing Publish-Subscribe Messaging and Message Queuing
Publish-Subscribe Messaging systems play an important role in any enterprise architecture as it enables reliable integration without tightly coupling the applications. The ability to share data between decoupled systems is not a problem that is easily tackled.
Consider an enterprise with multiple applications that are being built independently, with different languages and platforms. It needs to share data and processes responsively. We can achieve this using Messaging to transfer packets of data frequently, immediately, reliably, and asynchronously, using customizable formats. Asynchronous messaging is fundamentally a pragmatic reaction to the problems of distributed systems. Sending a message does not require both systems to be up and ready at the same time.