Slide Show is a "client context" demo. If you open another slide show, the slide sequence is independent for each show. Each slide show client has it's own context on the server.
In a real application, information would be presented as it becomes available at the server, rather than at a fixed interval.
The demo also subscribes to broadcast messages. The idea is that the broadcast represents some kind of out of band event that the user needs to be notified about. The message is stripped of tags before being displayed, insuring a text only message.