http://www.rfc-editor.org/rfc/rfc3995.txt
RFC 3995: Internet Printing Protocol (IPP): Event Notifications and Subscriptions, R. Herriot, T. Hastings2005-03-01T23:00:00-00:00 A client associates Subscription Objects with a particular Job by performing the Create-Job-Subscriptions operation or by submitting a Job with subscription information. A client associates Subscription Objects with the Printer by performing a Create-Printer-Subscriptions operation. Four other operations are defined for Subscription Objects: Get-Subscriptions-Attributes, Get-Subscriptions, Renew-Subscription, and Cancel-Subscription. [STANDARDS-TRACK]