I forgot to include a very important agreement which Lee's minutes included:
23. We agreed that the 'indp:' scheme would be the REQUIRED notification
delivery scheme that a Printer MUST accept in a Subscription Creation
request and either perform the delivery of Event Notifications using this
method or enlist a Notification Service to delivery Event Notifications
using this delivery method on the Printer's behalf. In order to reduce
confusion between the indp: delivery method and the INDP (IPP Notification
Delivery Protocol), the latter will be renamed to INSP (IPP Notification
Service Protocol). The indp: delivery method is sent by a Notification
Source (Printer or Notification Service) to a Notification Recipient and
happens to be the same as the Send-Notifications operation in the INSP
protocol which is sent from a Printer to a Notification Service.