What is "Focus" in AMPS?

A message that matches a subscription's topic and content filter is said to be "In Focus" for that subscription. AMPS will deliver messages that are "In Focus" for any subscription. However, sophisticated messaging applications may need to know when a message not only matches a subscription, but when it's updated so that it no longer matches a subscription, or becomes "Out of Focus".

A subscription can, optionally, request that AMPS sends notifications when a message becomes "Out of Focus". The subscription must provide the oof option explicitly to receive notifications.

The AMPS User Guide section on Out-of-Focus Messages (OOF) describes oof notifications, including the information provided to the application with a notification.