Most airlines board their passengers in some kinds of groups. So, announcements are made to get the people in the correct groups to board. A common way to do this is for the gate agent to announce that "Group n" is to board now. Perhaps it would be cool to page all the people in the appropriate group and have them rock up to board. Sounds like fun (and remember folks this is just an illustration). So if you were delivering messages to the smartphone or whever, you would simly send the message. Easy in an event based system?
Not so fast. Current systems probably don't recognize a legitimate event for this. It is procedure and policy (+ experience, queue monotoring, temperature on the jet bridge, screaming children,....) that actually triggers announcement - the what I call the "Microphone event". So how would we systematize that?
Change the gate agent system to do this - and think about the complexity involved, and the myriad of other delivered messages?
Automate the system to do something really clever, like start the boarding process clock at t-30 minutes, monitor the number of boarding pases lifted/scanned (as a proxy for queue depth), and when that number approximates the number of people in the group, then release the next group....
This brings up the point, that where we have humans sensing and responding to situations, they will raise events and deliver them through a variety of ways. Sometimes shouting throughh the mic is best of all. But if it does become desirable to do these kinds of things automatically, then use what the people do as cues for the kinds of events that the system needs to generate, sense and respond.