1. Alerting Scenario
CAP message sent at 20:00:00
It is a <msgType>Alert
Message effective at 20:00:00
Event onset in 30 minutes 20:30:00
Message expires at 22:00:00
Alert has been issued
- Message set to play for 2 hours starting right now - from 20:00:00 until 22:00:00

2. Event ends - its over at 21:00:00
- Do we Update or Cancel?
<msgType>Update
<msgType>Cancel

3. Questions? Should we use Update or Cancel or does it matter?
With multiple <info> blocks, it needs to be Update when not all <info> blocks are ended, so why use Cancel at all?
Does Cancel allow originators and distributors to do something different?
Does Cancel mean “It never happened”? As opposed to Update with an expires meaning “it happened and its over”?
Is there a different <headline> for the two?
Should there be an AllClear option to distinguish “its over” vs. “not happened”