14.  Appendix 4: Publish-Subscribe template

14.1  Principle

The Publish-Subscribe model is very different from the HTTP Request-Response cycle. This model enables a Publisher to push messages to a Subscriber in real time. An intermediary service (Broker) is the central point responsible for receiving messages and forwarding them to legitimate clients. Each message is published with a Topic, which is used to route messages through the intermediary service. Each customer who wishes to receive messages subscribes to one or more categories (Topics). The service delivers all messages corresponding to the Topics to which the customer has subscribed. In this way, customers and senders don't have to know each other, just the name of the Topic (and, of course, the name of the service). The sender publishes as he pleases, without...