I have just downloaded the latest spec for notification:
ftp://ftp.pwg.org/pub/pwg/ipp/new_NOT/ipp-not-spec-000424-rev.doc
This document has the following changes. It has not yet been carefully
checked for sections that these changes affect. Rather the changes have been
made to present the ideas.
A quick summary of the changes is:
The number of Printer events has been changed from 20 to 13, and the number
of job events been changed from 29 to 13. There is a new attribute
"notify-attributes" that contains additional attributes for a Print to
return in event notifications. Support in both Printer and client is
optional. This attribute is in job creation and subscription creation
operations.
The Printer "notify-attributes-supported" attribute lists all attributes
that a Printer supports in the notify-attributes. There is no default
attribute because the default is always no attributes.
The job-notify (1setOf collection) attribute is removed from job creation
operation and replaced by the member attributes "notify-xxx"
(subscriber-user-data is rename notify-user-data). Thus only one
subscription can be created with a job creation and collections are
unnecessary.
'None' is removed.