CMPWG 4-12-2012:

The Priority of a subscription is currently described as:

"Indicates the relative priority of the Subscription. When more than one Subscription needs to send Notifications, the Server should dequeue a Publish request to the Subscription with the highest priority number. For Subscriptions with equal priority the Server should dequeue Publish requests in a round-robin fashion. When the keep-alive period expires for a Subscription it shall take precedence regardless of its priority, in order to prevent the Subscription from expiring.
A Client that does not require special priority settings should set this value to zero."

This explanation does not describe how to prevent a subscription from never being serviced, except when its keep alive period matures. Here's a pseudo of our current thoughts/concerns:

1. create 2 subscriptions with different priorities, e.g. 10 and 30.
2. add several items to both subscriptions.
3. call Publish; you get data from sub with priority = 30.
   -- now suppose items change value in sub where priority = 30
4. call Publish and ack the last sequence; which subscription is received now?
   a. subscription with priority = 30 because it has the higher priority?
   b. subscription with priority = 10 because it is next in line? (doubtful)

How about when you scale this up to 3 subscriptions with priorities: 10, 20, and 30 etc.