The Publish & Subscribe EIP explains how to handle a scenario where one needs to publish events to all the interested parties without maintaining any hard coupling between them.
The following image extracted from the Enterprise Integration Patterns book by Gregor Hohpe illustrates an address changed message being sent to a set of subscribers who have subscribed to receive address changed messages:
If you are a frequent air traveller, you must be definitely worried about getting updates about your flight status. There are many channels that you can subscribe to. It can be over SMS, E-mail or even you can have an Apple or Android app on your mobile phone. Also, you can see electronic flight status boards hanging at the airport itself.
All these flight status updates are generated from a single source and broadcast to all the interested parties. If you are interested in getting updates, you can subscribe to the channel you want. Also you should...