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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 3995

Internet Printing Protocol WG                        R. Herriot (editor)
INTERNET-DRAFT                                               T. Hastings
<draft-ietf-ipp-not-spec-07.txt>                             M. Shepherd
Updates RFC 2910 and 2911                              Xerox Corporation
[Target Category: standards track]                              R. deBry
Expires:  February 20, 2002                    Utah Valley State College
                                                             S. Isaacson
                                                            Novell, Inc.
                                                               J. Martin
                                                              Underscore
                                                              R. Bergman
                                          Hitachi Koki Imaging Solutions
                                                         August 20, 2001
                     Internet Printing Protocol (IPP):
                 IPP Event Notifications and Subscriptions

      Copyright (C) The Internet Society (2001). All Rights Reserved.

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [RFC2026].  Internet-Drafts are
   working documents of the Internet Engineering Task Force (IETF), its
   areas, and its working groups.  Note that other groups may also
   distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed as
   http://www.ietf.org/shadow.html.

Abstract

   This document describes an OPTIONAL extension to the Internet
   Printing Protocol/1.0 (IPP) [RFC2566, RFC2565] and IPP/1.1 [RFC2911,
   RFC2910].  This extension allows a client to subscribe to printing
   related Events.  Subscriptions are modeled as Subscription Objects.
   The Subscription Object specifies that when one of the specified
   Events occurs, the Printer sends an asynchronous Event Notification
   to the specified Notification Recipient via the specified Delivery
   Method (i.e., protocol).  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

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   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.













































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Table of Contents


   1 Introduction.....................................................7
   1.1 Notification Overview..........................................7

   2 Models for Notification.........................................10
   2.1 Model for Notification (Simple Case)..........................10
   2.2 Model for Notification with Cascading Printers................10
   2.3 Distributed Model for Notification............................11
   2.4 Extended Notification Recipient...............................11

   3 Terminology.....................................................11
   3.1 Conformance Terminology.......................................12
   3.2 Other Terminology.............................................12

   4 Object Relationships............................................15
   4.1 Printer and Per-Printer Subscription Objects..................15
   4.2 Printer, Job and Per-Job Subscription Objects.................15

   5 Subscription Object.............................................15
   5.1 Rules for Support of Subscription Template Attributes.........16
   5.2 Rules for Processing Subscription Template Attributes.........17
   5.3 Subscription Template Attributes..............................21
   5.3.1 notify-recipient-uri (uri)..................................22
   5.3.2 notify-events (1setOf type2 keyword)........................23
   5.3.2.1 Standard Values for Subscribed Events.....................24
   5.3.2.1.1 No Events...............................................24
   5.3.2.1.2 Subscribed Printer Events...............................24
   5.3.2.1.3 Subscribed Job Events...................................26
   5.3.2.2 Rules for Matching of Subscribed Events...................27
   5.3.2.2.1 Rules for Matching of Printer Events....................27
   5.3.2.2.2 Rules for Matching of Job Events........................28
   5.3.2.2.3 Special Cases for Matching Rules........................29
   5.3.3 notify-attributes (1setOf type2 keyword)....................30
   5.3.4 notify-user-data (octetString(63))..........................31
   5.3.5 notify-charset (charset)....................................32
   5.3.6 notify-natural-language (naturalLanguage)...................32
   5.3.7 notify-lease-duration (integer(0:67108863)).................33
   5.3.8 notify-time-interval (integer(0:MAX)).......................34
   5.4 Subscription Description Attributes...........................35
   5.4.1 notify-subscription-id  (integer (1:MAX))...................36
   5.4.2 notify-sequence-number (integer (0:MAX))....................37
   5.4.3 notify-lease-expiration-time (integer(0:MAX))...............37
   5.4.4 notify-printer-up-time (integer(1:MAX)).....................38
   5.4.5 notify-printer-uri (uri)....................................39
   5.4.6 notify-job-id (integer(1:MAX))..............................39
   5.4.7 notify-subscriber-user-name (name(MAX)).....................39

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   6 Printer Description Attributes Related to Notification..........40
   6.1 printer-state-change-time (integer(1:MAX))....................40
   6.2 printer-state-change-date-time (dateTime).....................41

   7 New Values for Existing Printer Description Attributes..........41
   7.1 operations-supported (1setOf type2 enum)......................41

   8 Attributes Only in Event Notifications..........................42
   8.1 notify-subscribed-event (type2 keyword).......................42
   8.2 notify-text (text(MAX)).......................................43

   9 Event Notification Content......................................43
   9.1 Content of Machine Consumable Event Notifications.............46
   9.1.1 Event Notification Content Common to All Events.............46
   9.1.2 Additional Event Notification Content for Job Events........48
   9.1.3 Additional Event Notification Content for Printer Events....49
   9.2 Content of Human Consumable Event Notification................49
   9.2.1 Event Notification Content Common to All Events.............50
   9.2.2 Additional Event Notification Content for Job Events........52
   9.2.3 Additional Event Notification Content for Printer Events....53

   10 Delivery Methods...............................................54

   11 Operations for Notification....................................56
   11.1 Subscription Creation Operations.............................56
   11.1.1 Create-Job-Subscriptions Operation.........................57
   11.1.1.1 Create-Job-Subscriptions Request.........................57
   11.1.1.2 Create-Job-Subscriptions Response........................58
   11.1.2 Create-Printer-Subscriptions operation.....................59
   11.1.2.1 Create-Printer-Subscriptions Request.....................60
   11.1.2.2 Create-Printer-Subscriptions Response....................60
   11.1.3 Job Creation Operations - Extensions for Notification......60
   11.1.3.1 Job Creation Request.....................................61
   11.1.3.2 Job Creation Response....................................62
   11.2 Other Operations.............................................63
   11.2.1 Restart-Job Operation - Extensions for Notification........63
   11.2.2 Validate-Job Operation - Extensions for Notification.......63
   11.2.3 Get-Printer-Attributes - Extensions for Notification.......64
   11.2.4 Get-Subscription-Attributes operation......................64
   11.2.4.1 Get-Subscription-Attributes Request......................65
   11.2.4.2 Get-Subscription-Attributes Response.....................66
   11.2.5 Get-Subscriptions operation................................67
   11.2.5.1 Get-Subscriptions Request................................67
   11.2.5.2 Get-Subscriptions Response...............................69
   11.2.6 Renew-Subscription operation...............................70
   11.2.6.1 Renew-Subscription Request...............................70
   11.2.6.2 Renew-Subscription Response..............................71
   11.2.7 Cancel-Subscription operation..............................72

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   11.2.7.1 Cancel-Subscription Request..............................73
   11.2.7.2 Cancel-Subscription Response.............................73

   12 Conformance Requirements.......................................74

   13 IANA Considerations............................................75
   13.1 Attribute Registrations......................................76
   13.2 Additional Enum Attribute Value Registrations for the
   "operations-supported" Printer Attribute..........................77
   13.3 Operation Registrations......................................77
   13.4 Status code Registrations....................................78
   13.5 Attribute Group tag Registrations............................78
   13.6 Registration of Events.......................................78
   13.7 Registration of Event Notification Delivery Methods..........79
   13.7.1 Requirements for Registration of Event Notification Delivery
              Methods................................................79
   13.7.1.1 Required Characteristics.................................79
   13.7.1.2 Naming Requirements......................................80
   13.7.1.3 Functionality Requirements...............................80
   13.7.1.4 Usage and Implementation Requirements....................80
   13.7.1.5 Publication Requirements.................................80
   13.7.2 Registration Procedure.....................................81
   13.7.2.1 Present the proposal to the Community....................81
   13.7.2.2 Delivery Method Reviewer.................................81
   13.7.2.3 IANA Registration........................................81
   13.7.3 Delivery Method Document Registrations.....................82
   13.7.4 Registration Template......................................82

   14 Internationalization Considerations............................82

   15 Security Considerations........................................83

   16 Status Codes...................................................84
   16.1 successful-ok-ignored-subscriptions (0x0003).................84
   16.2 client-error-ignored-all-subscriptions (0x0414)..............84

   17 Status Codes in Subscription Attributes Groups.................84
   17.1 client-error-uri-scheme-not-supported (0x040C)...............85
   17.2 client-error-too-many-subscriptions (0x0415).................85
   17.3 successful-ok-too-many-events (0x0005).......................85
   17.4 successful-ok-ignored-or-substituted-attributes (0x0001).....85

   18 Encodings of Additional Attribute Tags.........................85

   19 References.....................................................86

   20 Author's Addresses.............................................87


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   A. Appendix - Model for Notification with Cascading Printers......89

   B. Appendix - Distributed Model for Notification..................90

   C. Appendix - Extended Notification Recipient.....................91

   D. Appendix - Details about Conformance Terminology...............93

   E. Appendix - Object Model for Notification.......................93
   E.1  Appendix - Object relationships..............................94
   E.2  Printer Object and Per-Printer Subscription Objects..........95
   E.3  Job Object and Per-Job Subscription Objects..................95

   F. Appendix - Per-Job versus Per-Printer Subscription Objects.....95

   G. Appendix - Description of the base IPP documents...............96

   H. Appendix - Full Copyright Statement............................97

Tables
   Table 1 - Subscription Template Attributes........................22
   Table 2 - Subscription Description Attributes.....................36
   Table 3 - Printer Description Attributes Associated with Notification
       ..............................................................40
   Table 4 - Operation-id assignments................................42
   Table 5 - Attributes in Event Notification Content................47
   Table 6 - Additional Event Notification Content for Job Events....48
   Table 7 - Combinations of Events and Subscribed Events for "job-
      impressions-completed" ........................................49
   Table 8 - Additional Event Notification Content for Printer Events49
   Table 9 - Printer Name in Event Notification Content..............51
   Table 10 - Event Name in Event Notification Content...............51
   Table 11 - Event Time in Event Notification Content...............52
   Table 12 - Job Name in Event Notification Content.................52
   Table 13 - Job State in Event Notification Content................53
   Table 14 - Printer State in Event Notification Content............54
   Table 15 - Information about the Delivery Method..................55
   Table 16 - Printer Conformance Requirements for Operations........75

Figures
   Figure 1 - Model for Notification.................................10
   Figure 2 - Model for Notification with Cascading Printers.........90
   Figure 3 - Opaque Use of a Notification Service Transparent to the
      Client ........................................................91
   Figure 4 - Use of an Extended Notification Recipient transparent to
      the Printer ...................................................92
   Figure 5 - Object Model for Notification..........................94


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1 Introduction

   This IPP notification specification is an OPTIONAL extension to
   Internet Printing Protocol/1.0 (IPP) [RFC2566, RFC2565] and IPP/1.1
   [RFC2911, RFC2910].  See Appendix G for a description of the base IPP
   documents.  This document in combination with the following documents
   is intended to meet the notification requirements described in [ipp-
   not-req]:

         Internet Printing Protocol (IPP):  "Job Progress Attributes"
         [ipp-prog]
         One or more Delivery Method Documents registered with IANA (see
         section 10).

   Note: this document does not define any Delivery Methods, but it does
   define the rules for conformance for Delivery Method Documents.
   Delivery Method Documents are in preparation (see section 10) and
   will be registered with IANA (see section 13.7.3).

   Refer to the Table of Contents for the layout of this document.


1.1 Notification Overview

   This document defines operations that a client can perform in order
   to create Subscription Objects in a Printer and carry out other
   operations on them. A Subscription Object represents a Subscription
   abstraction. The Subscription Object specifies that when one of the
   specified Events occurs, the Printer sends an asynchronous Event
   Notification to the specified Notification Recipient via the
   specified Delivery Method (i.e., protocol).

   When a client (called a Subscribing Client) performs an operation
   that creates a Subscription Object, the operation contains one or
   more Subscription Template Attributes Groups. Each such group holds
   information used by the Printer to initialize a newly created
   Subscription Object. The Printer creates one Subscription Object for
   each Subscription Template Attributes Group in the operation. This
   group is like the Job Template Attributes group defined in [RFC2911].
   The following is an example of the information included in a
   Subscription Template Attributes Group (see section 5 for details on
   the Subscription Object attributes):

     1.The names of Subscribed Events that are of interest to the
       Notification Recipient.
     2.The address (URL) of one Notification Recipient.
     3.The Delivery Method (i.e., the protocol) which the Printer uses
       to send the Event Notification.

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     4.Some opaque data that the Printer sends to the Notification
       Recipient in the Event Notification. The Notification Recipient
       might use this opaque data as a forwarding address for the Event
       Notification.
     5.The charset to use in text fields within an Event Notification
     6.The natural language to use in the text fields of the Event
       Notification
     7.The requested lease time in seconds for the Subscription Object
   An operation that creates a Subscription Object is called a
   Subscription Creation Operation. These operations include the
   following operations (see section 11.1 for further details):

      -  Job Creation operation: When a client performs such an
         operation (Print-Job, Print-URI, and Create-Job), a client can
         include zero or more Subscription Template Attributes Groups in
         the request.  The Printer creates one Subscription Object for
         each Subscription Template Attributes Group in the request, and
         the Printer associates each such Subscription Object with the
         newly created Job. This document extends these operations'
         definitions in [RFC2911] by adding Subscription Template
         Attributes Groups in the request and Subscription Attributes
         Groups in the response.

      -  Create-Job-Subscriptions operation: A client can include one or
         more Subscription Template Attributes Groups in the request.
         The Printer creates one Subscription Object for each
         Subscription Template Attributes Group and associates each with
         the job that is the target of this operation.

      -  Create-Printer-Subscriptions operation: A client can include
         one or more Subscription Template Attributes Groups in the
         request.  The Printer creates one Subscription Object for each
         Subscription Template Attributes Group and associates each with
         the Printer that is the target of this operation.

   For each of the above operations:

      -  the Printer associates a Subscription Object with the Printer
         or a specific Job. When a Subscription Object is associated
         with a Job Object, it is called a Per-Job Subscription Object.
         When a Subscription Object is associated with a Printer Object,
         it is called a Per-Printer Subscription Object.

      -  the response contains one Subscription Attributes Group for
         each Subscription Template Attributes Group in the request and
         in the same order. When the Printer successfully creates a
         Subscription Object, its corresponding Subscription Attributes
         Group contains the "notify-subscription-id" attribute. This

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         attribute uniquely identifies the Subscription Object and is
         analogous to a "job-id" for a Job object. Some operations
         described below use the "notify-subscription-id" to identify
         the target Subscription Object.

   This document defines the following additional operations (see
   section 11.2 for further details):

      -  Restart-Job operation: When a client performs the Restart-Job
         operation [RFC2911], the Printer re-uses the same Job and its
         Subscription Objects.

      -  Validate-Job operation: When a client performs this operation,
         a client can include zero or more Subscription Template
         Attributes Groups in the request.  The Printer determines if it
         could create one Subscription Object for each Subscription
         Template Attributes Group in the request. This document extends
         this operation's definition in [RFC2911] by adding Subscription
         Template Attributes Groups in the request and Subscription
         Attributes Groups in the response.

      -  Get-Subscription-Attributes operation: This operation allows a
         client to obtain the specified attributes of a target
         Subscription Object.

      -  Get-Subscriptions operation: This operation allows a client to
         obtain the specified attributes of all Subscription Objects
         associated with the Printer or a specified Job.

      -  Renew-Subscription operation: This operation renews the lease
         on the target Per-Printer Subscription Object before it
         expires. A newly created Per-Printer Subscription Object
         receives an initial lease.  It is the duty of the client to use
         this operation frequently enough to preserve a Per-Printer
         Subscription Object. The Printer deletes a Per-Printer
         Subscription Object when its lease expires. A Per-Job
         Subscription Object last exactly as long as its associated Job
         Object and thus doesn't have a lease.

      -  Cancel-Subscription operation: This operation (1) cancels the
         lease on the specified Per-Printer Subscription Object and
         thereby deletes the Per-Printer Subscription Object or (2)
         deletes the Per-Job Subscription Object.

   When an Event occurs, the Printer finds all Subscription Objects
   listening for the Event (see section 9 for details on finding such
   Subscription Objects). For each such Subscription Object, the
   Printer:

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     a)generates an Event Notification with information specified in
       section 9, AND
     b)either:
       i)   delivers the Event Notification using the Delivery Method
          and target address identified in the Subscription Object's
          "notify-recipient-uri" attribute if the Delivery Method is a
          "push", OR
       ii)  saves Event Notification for a time period defined by the
          Delivery Method if the Delivery Method is a "pull", i.e., the
          Notification Recipient is expected to fetch the Event
          Notifications.

2 Models for Notification


2.1 Model for Notification (Simple Case)

   As part of a Subscription Creation Operation, an IPP Printer (i.e.,
   located in an output device or a server) creates one or more
   Subscription Objects. In a Subscription Creation Operation, the
   client specifies the Notification Recipient to which the Printer is
   to deliver Event Notifications.  A Notification Recipient can be the
   Subscribing Client or a third party.

   Figure 1 shows the Notification model for a simple Client-Printer
   relationship.


   embedded printer:
                                           output device or server
      PDA, desktop, or server                 +---------------+
           +--------+                         |  ###########  |
           | client |-----Subscription ---------># Printer #  |
           +--------+  Creation Operation     |  # Object  #  |
        +------------+                        |  #####|#####  |
        |Notification|                        +-------|-------+
        |Recipient   |<----IPP Event Notifications----+
        +------------+    (Job and/or Printer Events)

                     Figure 1 - Model for Notification


2.2 Model for Notification with Cascading Printers

   With this model, there is an intervening Print server between the
   human user and the Printer in the output device. If the Printer in
   the output device generates an Event, the system can be configured to
   send Event Notification either

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      -  directly to the Notification Recipient specified by the
         Subscribing Client or

      -  via the Print Server to the Notification Recipient specified by
         the Subscribing Client.

   See Appendix A for more details.


2.3 Distributed Model for Notification

   The preceding sections (2.1 and 2.2) assume that the Notification
   software resides in the same device or Server box as the rest of the
   Printer software. In many implementations, the assumption is correct.
   However, the Notification model also permits a distributed
   implementation.

   For example, the software that supports both Subscription Creation
   Operations and sending of Event Notifications could be on hardware
   that is separate from the output device. To make this work, there
   must be a symbiotic relationship between the output device software
   and the remote Notification software. Without the remote Notification
   software, the output device software is not a complete Printer.

   The term "Printer" in this document includes the software on the
   output device or server box as well as Notification software that is
   local to or remote from the output device.

   Appendix B describes this example in detail.


2.4 Extended Notification Recipient

   The model allows for an extended Notification Recipient that is
   itself a Notification service that forwards each Event Notification
   to another recipient. The client contacts this Notification Recipient
   to arrange for forwarding by means outside the scope of this
   document. The Printer need not be aware that the Notification
   Recipient forwards Event Notifications.

   Appendix C describes this example in detail.


3 Terminology

   This section defines terminology used throughout this document. Other
   terminology is defined in [RFC2911].


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3.1 Conformance Terminology

   Capitalized terms, such as MUST, MUST NOT, REQUIRED, SHOULD, SHOULD
   NOT, MAY, NEED NOT, and OPTIONAL, have special meaning relating to
   conformance as defined in RFC 2119 [RFC2119] and [RFC2911] section
   12.1.  If an implementation supports the extension defined in this
   document, then these terms apply; otherwise, they do not.  These
   terms define conformance to this document only; they do not affect
   conformance to other documents, unless explicitly stated otherwise.
   See Appendix D for complete details.

   Note: a feature that is OPTIONAL in this document becomes REQUIRED if
   the Printer implements a Delivery Method that REQUIRES the feature.

   READ-ONLY - an adjective used in an attribute definition to indicate
      that an IPP Printer MUST NOT allow the attribute's value to be
      modified with the Set-Job-Attributes or Set-Printer-Attributes
      operations (see [ipp-set]).  Note:  there is no Set-Subscription
      operation so this term is not used for Subscription object
      attributes.


3.2 Other Terminology

   This document uses the same terminology as [RFC2911], such as
   "client", "Printer", "attribute", "attribute value", "keyword",
   "operation", "request", "response", and "support".  In addition, the
   following terms are defined for use in this document and the Delivery
   Method Documents:

   Administrator - A human user who establishes policy for and
      configures the print system.

   Operator - A human user who carries out the policy established by the
      Administrator and controls the day to day running of the print
      system.

   IPP Client (or client) - The software component (PDA, desktop, or
      server) that performs an IPP operation directed at an IPP Printer
      (located in a server or output device).

   Job Creation operation - One of the operations that creates a Job
      object:  Print-Job, Print-URI and Create-Job.  The Restart-Job
      operation [RFC2911] is not considered a Job Creation operation,
      since the Printer re-uses the existing Job object.  The Validate-
      Job operation is not a Job Creation operation because no Job
      object is created.  Therefore, when a statement also applies to
      the Validate-Job operation, it is mentioned explicitly.

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   Event - some occurrence (either expected or unexpected) within the
      printing system of a change of state, condition, or configuration
      of a Job or Printer object. An Event occurs only at one instant in
      time and does not span the time the physical Event takes place.
      For example, jam-occurred and jam-cleared are two distinct,
      instantaneous Events, even though the jam may last for a while.

   Event Notification - the information about an Event that the Printer
      sends when an Event occurs.

   Compound Event Notification - two or more Event Notifications that a
      Printer sends together as a single entity.  The Delivery Method
      Document specifies whether the Delivery Method supports Compound
      Event Notifications.

   Job Event - an Event caused by some change in a particular job on the
      Printer, e.g., 'job-completed'.

   Printer Event - an Event caused by some change in the Printer that is
      not specific to a job, e.g., 'printer-state-changed'.

   Subscribed Event - an Event that the Subscribing Client expresses
      interest in by making it a value of the "notify-events" attribute
      on a Subscription Object.

   Subscribed Job Event - a Subscribed Event that is a Job Event.

   Subscribed Printer Event - a Subscribed Event that is a Printer
      Event.

   Notification Recipient - the entity to which the Printer sends an
      Event Notification.

   Delivery Method - the mechanism by which the Printer delivers the
      Event Notification, e.g., via email or via an Event Notification
      Delivery Method protocol defined for delivering IPP Event
      Notifications.

   Delivery Method Document - a document, separate from this document,
      that defines a Delivery Method.

   Subscription Object - An object containing a set of attributes that
      indicate: the Notification Recipient, the Delivery Method, the
      Subscribed Events that cause the Printer to send an Event
      Notification, and the information to send in an Event
      Notification.



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   Per-Job Subscription Object - A Subscription Object that is
      associated with a single Job. The Create-Job-Subscriptions
      operation and Job Creation operations create such an object.

   Per-Printer Subscription Object - A Subscription Object that is
      associated with the Printer as a whole. The Create-Printer-
      Subscriptions operation creates such an object.

   Subscribing Client - The client that creates the Subscription Object.

   Subscription Creation Operation - An operation that creates a
      Subscription Object:  Job Creation operations, Create-Job-
      Subscriptions operation, Create-Printer-Subscriptions operation.
      In the context of a Job Creation operation, a Subscription
      Creation Operation is the part of the Job Creation operation that
      creates a Subscription object.  The Restart-Job operation
      [RFC2911] is not considered a Subscription Creation Operation,
      since the Printer re-uses the Job's existing Subscription Objects,
      rather than creating any new Subscription Objects.

   Subscription Creation Request - The request portion of a Subscription
      Creation Operation.

   Subscription Template Attributes - Subscription Object attributes
      that a client can supply in a Subscription Creation Operation and
      associated Printer Object attributes that specify supported and
      default values for the Subscription Object attributes.

   Subscription Description Attributes - Subscription Object attributes
      that a Printer supplies during a Subscription Creation Operation.

   Subscription Template Attributes Group - The attributes group in a
      request that contains Subscription Object attributes that are
      Subscription Template Attributes.

   Subscription Attributes Group - The attributes group in a response
      that contains Subscription Object attributes.

   Human Consumable Event Notification - localized text for human
      consumption only.  There is no standardized format and thus
      programs should not try to parse this text.

   Machine Consumable Event Notification - bytes for program
      consumption. The bytes are formatted according to the Delivery
      Method document.

   Printer - the software that supports an output device or print server
      (see IPP/1.1 [RFC2911] which uses the terms Printer and Printer

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      object interchangeably). This document extends the IPP/1.1 Printer
      definition to include the software that implements Subscription
      Creation Operations and the sending of Event Notifications, even
      if the software for such a Printer would be distributed across a
      network (see section 2.3).

   Notification - when not in the phrases 'Event Notification' and
      'Notification Recipient' - the concepts of this specification,
      i.e., Events, Subscription Objects, and Event Notifications.


4 Object Relationships

   This section defines the object relationships between the Printer,
   Job, and Subscription Objects.  It does not define the
   implementation. For an illustration of these relationships, see
   Appendix E.


4.1 Printer and Per-Printer Subscription Objects

    1.A Printer object can be associated with zero or more Per-Printer
      Subscription Objects.

    2.Each Per-Printer Subscription Object is associated with exactly
      one Printer object.


4.2 Printer, Job and Per-Job Subscription Objects

    1.A Printer object is associated with zero or more Job objects.

    2.Each Job object is associated with exactly one Printer object.

    3.A Job object is associated with zero or more Per-Job Subscription
      Objects.

    4.Each Per-Job Subscription Object is associated with exactly one
      Job object.


5 Subscription Object

   A Subscribing Client creates a Subscription Object with a
   Subscription Creation Operation in order to indicate its interest in
   certain Events. See section 11 for a description of these operations.
   When an Event occurs, the Subscription Object specifies to the
   Printer where to send Event Notifications, how to send them and what

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   to put in them. See section 9 for details on the contents of an Event
   Notification.

   Using the IPP Job Template attributes as a model (see [RFC2911]
   section 4.2), the attributes of a Subscription Object are divided
   into two categories: Subscription Template Attributes and
   Subscription Description Attributes.

   Subscription Template attributes are, in turn, like the Job Template
   attributes, divided into

     1.Subscription Object attributes that a client can supply in a
       Subscription Creation Request and

     2.their associated Printer Object attributes that specify
       supported and default values for the Subscription Object
       attributes

   The remainder of this section specifies general rules for
   Subscription Template Attributes and describes each attribute in a
   Subscription Object.


5.1 Rules for Support of Subscription Template Attributes

   Subscription Template Attributes are fundamental to the Notification
   model described in this specification. The client supplies these
   attributes in Subscription Creation Operations and the Printer uses
   these attributes to populate a newly created Subscription Object.

   Subscription Objects attributes that are Subscription Template
   Attributes conform to the following rules:

     1.Each attribute's name starts with the prefix string "notify-"
       and this document calls such attributes "notify-xxx".

     2.For each "notify-xxx" Subscription Object attribute defined in
       column 1 of Table 1 in section 5.3, Table 1 specifies
       corresponding Printer attributes: "notify-xxx-default", "notify-
       xxx-supported", "yyy-supported" and "notify-max-xxx-supported"
       defined in column 2 of Table 1.  Note "xxx" stands for the same
       string in each case and "yyy" stands for some other string.

     3.If a Printer supports "notify-xxx" in column 1 of Table 1, then
       the Printer MUST support all associated attributes specified in
       column 2 of Table 1. For example, Table 1 shows that if the
       Printer supports "notify-events", it MUST support "notify-


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       events-default", "notify-events-supported" and "notify-max-
       events-supported".

     4.If a Printer does not support "notify-xxx" in column 1 of Table
       1, then the Printer MUST NOT support any associated "notify-yyy"
       attributes specified in column 2 of Table 1. For example, Table
       1 shows that if the Printer doesn't support "notify-events", it
       MUST NOT support "notify-events-default", "notify-events-
       supported" and  "notify-max-events-supported".  Note this rule
       does not apply to attributes whose names do not start with the
       string "notify-" and are thus defined in another object and used
       by other attributes.

     5.Most "notify-xxx" attributes have a corresponding "yyy-
       supported" attribute that specifies the supported values for
       "notify-xxx". Column 2 of Table 1 specifies the name of each
       "yyy-supported" attribute. The naming rules of IPP/1.1 (see
       [RFC2911]) are used when "yyy-supported" is "notify-xxx-
       supported".

     6.Some "notify-xxx" attributes have a corresponding "notify-xxx-
       default" attribute that specifies the value for "notify-xxx" if
       the client does not supply it. Column 2 of Table 1 specifies the
       name of each "notify-xxx-default" attribute. The naming rules of
       IPP/1.1 (see [RFC2911]) are used.

   If a client wishes to present an end user with a list of supported
   values from which to choose, the client SHOULD query the Printer for
   its supported value attributes.  The client SHOULD also query the
   default value attributes.  If the client then limits selectable
   values to only those values that are supported, the client can
   guarantee that the values supplied by the client in the create
   request all fall within the set of supported values at the Printer.
   When querying the Printer, the client MAY enumerate each attribute by
   name in the Get-Printer-Attributes Request, or the client MAY just
   supply the 'subscription-template' group name in order to get the
   complete set of supported attributes (both supported and default
   attributes - see section 11.2.3).


5.2 Rules for Processing Subscription Template Attributes

   This section defines a detailed set of rules that a Printer follows
   when it processes Subscription Template Attributes in a Subscription
   Creation Request. These rules are similar to the rules for processing
   Operation attributes in [RFC2911]. That is, the Printer may or may
   not support an attribute and a client may or may not supply the


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   attribute. Some combinations of these cases are OK. Others return
   warnings or errors, and perhaps a list of unsupported attributes.

   A Printer MUST implement the following behavior for processing
   Subscription Template Attributes in a Subscription Creation Request:

   1.If a client supplies a "notify-xxx" attribute from column 1 of
     Table 1 and the Printer supports it and its value, the Printer
     MUST populate the attribute on the created Subscription Object.

   2.If a client supplies a "notify-xxx" attribute from column 1 of
     Table 1 and the Printer doesn't support it or its value, the
     Printer MUST NOT populate the attribute on the created
     Subscription Object with it. The Printer MUST do one of the
     following:

     a) If the value of the "notify-xxx" attribute is unsupported, the
        Printer MUST return the attribute with its value in the
        Subscription Attributes Group of the response.

     b) If "notify-xxx" is an unsupported attribute, the Printer MUST
        return the attribute in the Subscription Attributes Group of the
        response with the 'unsupported' out-of-band value.

     Note:  The rules of this step are the same as for Unsupported
     Attributes [RFC2911] section 3.1.7. except that the unsupported
     attributes are returned in the Subscription Attributes Group
     rather than the Unsupported Attributes Group because Subscription
     Creation Operations can create more than one Subscription Object).

   3.If a client is REQUIRED to supply a "notify-xxx" attribute from
     column 1 of Table 1 and the Printer doesn't support the supplied
     value, the Printer MUST NOT create a Subscription Object. The
     rules for Unsupported Attributes in step #2 still apply.

   4.If a client does not supply a "notify-xxx" attribute from column 1
     of Table 1 and the attribute is REQUIRED for the client to supply,
     the Printer MUST reject the Subscription Creation Operation
     (including Job Creation operations) without creating a
     Subscription Object, and MUST return in the response:

     c) the status code 'client-error-bad-request' AND

     d) no Subscription Attribute Groups.

   5.If a client does not supply a "notify-xxx" attribute from column 1
     of Table 1 that is OPTIONAL for the client to supply, and column 2
     of Table 1 either:

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     a) specifies a "notify-xxx-default" attribute, the Printer MUST
        behave as if the client had supplied the "notify-xxx-default"
        attribute (see step #1) and populate the Subscription object
        with the value of the "notify-xxx-default" attribute as part of
        the Subscription Creation operation (unlike Job Template
        attributes where the Printer does not populate the Job object
        with defaults - see [RFC2911]) OR

     b) does not specify a "notify-xxx-default" attribute, the Printer
        MUST populate the "notify-xxx" attribute on the Subscription
        Object according to the definition of the "notify-xxx" attribute
        in a section 5.3. For some attributes, the "notify-xxx" is
        populated with the value of some other attribute, and for
        others, the "notify-xxx" is NOT populated on the Subscription
        object at all.

   6.A Printer MUST create a Subscription Object for each Subscription
     Template Attributes group in a request unless the Printer:

     a) encounters some attributes in a Subscription Template Attributes
        Group that require the Printer not to create the Subscription
        Object OR

     b) would create a Per-Job Subscription Object when it doesn't have
        space for another Per-Job Subscription Object OR

     c) would create a Per-Printer Subscription Object when it doesn't
        have space for another Per-Printer Subscription Object.

   7.A response MUST contain one Subscription Attributes Group for each
     Subscription Template Attributes Group in the request (and in the
     same order) whether the Printer creates a Subscription Object from
     the Subscription Template Attributes Group or not. However, the
     attributes in each Subscription Attributes Group can be in any
     order.

   8.The Printer MUST populate each Subscription Attributes Group of
     the response such that each contains:

     a) the "notify-subscription-id" attribute (see section 5.4.1), if
        and only if the Printer creates a Subscription Object.

     b) the "notify-lease-duration" attribute (see section 5.3.7), if
        and only if the Printer creates a Per-Printer Subscription
        Object. The value of this attribute is the value of the
        Subscription Object's "notify-lease-duration" attribute. This
        value MAY be different from the client-supplied value (see
        section 5.3.7). If a client supplies this attribute in the

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        creation of a Per-Job Subscription Object, it MUST appear in
        this group with the out-of-band value 'unsupported' to indicate
        that the Printer doesn't support it in this context.

     c) all of the unsupported Subscription Template Attributes from
        step #2.  Note, they are not returned in the Unsupported
        Attributes Group in order to separate the unsupported attributes
        for each Subscription Object.

     d) the "notify-status-code" attribute if the Printer does not
        create the Subscription Object or if there are unsupported
        attributes from step #2. The possible values of the "notify-
        status-code" attribute are shown below (see section 17 for more
        details). The Printer returns the first value in the list below
        that describes the status.

          'client-error-uri-scheme-not-supported':  the Subscription
             Object was not created because the scheme of the "notify-
             recipient-uri" attribute is not supported. See section 17.1
             for more details about this status code. See step #3 in
             this section for the case that causes this error, and the
             resulting step #6a) that causes the Printer not to create
             the Subscription Object.

          'client-error-too-many-subscriptions':  the Subscription
             Object was not created because the Printer has no space for
             additional Subscription Objects.  The client SHOULD try
             again later. See section 17.2 for more details about this
             status code. See steps #6b) and #6c) in this section for
             the cases that causes this error.

          'successful-ok-too-many-events':  the Subscription Object was
             created without the "notify-events" values included in this
             Subscription Attributes Group because the "notify-events"
             attribute contains too many values. See section 17.3 for
             more details about this status code. See step #2 in this
             section and section 5.3.2 for the cases that cause this
             status code.

          'successful-ok-ignored-or-substituted-attributes' :  the
             Subscription Object was created but some supplied
             Subscription Template Attributes are unsupported. These
             unsupported attributes are also in the Subscription
             Attributes Group. See section 17.4 for more details about
             this status code. See step #2 in this section for the cases
             that cause this status code.



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   9.The Printer MUST validate all Subscription Template Attributes and
     MUST return all unsupported attributes and values in the
     corresponding Subscription Attributes Group of the response (see
     step #2) unless it determines that it could not create additional
     Subscription Objects because of condition #6b) or condition #6c).
     Then, the Printer NEED NOT validate these additional Subscription
     Template Attributes and the client MUST NOT expect to find
     unsupported attributes from step #2 in such additional
     Subscription Attribute Groups.


5.3 Subscription Template Attributes

   This section contains the Subscription Template Attributes defined
   for the Subscription and Printer objects.

   Table 1 below shows the Subscription Template Attributes and has two
   columns:

      -  Attribute in Subscription Object: the name and attribute syntax
         of each Subscription Object Attribute that is a Subscription
         Template Attribute

      -  Default and Supported Printer Attributes: the default attribute
         and supported Printer attributes that are associated with the
         attribute in column 1.

   A Printer MUST support all attributes in Table 1 below except for
   "notify-attributes" (and "notify-attributes-supported").  A client
   MUST supply "notify-recipient-uri" and MAY omit any of the rest of
   the attributes in column 1 of Table 1 in a Subscription Creation
   Request.

   Note:  The Default and Supported Printer attributes listed in column
   2 of Table 1 do not have separate sections in this specification
   defining their semantics.  Instead, the section for the corresponding
   Subscription Object attribute (column 1 of Table 1) contains the
   semantics of these Printer attributes.  This approach follows the
   precedence of the Job Template attributes in section 4.2 of [RFC2911]
   where the corresponding "xxx-default" and "xxx-supported" Printer
   attributes are defined in the same section as the "xxx" Job
   attribute.







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                Table 1 - Subscription Template Attributes


   Attribute in Subscription     Default and Supported Printer
   Object                        Attributes


   notify-recipient-uri (uri)    notify-schemes-supported  (1setOf
                                 uriScheme)

   notify-events (1setOf type2         -events-default (1setOf type2
   keyword)                      keyword)
                                 notify-events-supported (1setOf type2
                                 keyword)
                                 notify-max-events-supported
                                 (integer(2:MAX))

   notify-attributes (1setOf     notify-attributes-supported (1setOf
   type2 keyword)                type2 keyword)

   notify-user-data
   (octetString(63))

   notify-charset (charset)      charset-supported (1setOf charset)

   notify-natural-language       generated-natural-language-supported
   (naturalLanguage)             (1setOf naturalLanguage)

   notify-lease-duration         notify-lease-duration-default
   (integer(0:MAX))              (integer(0:67108863))
                                 notify-lease-duration-supported
                                 (1setOf (integer(0: 67108863) |
                                 rangeOfInteger(0:67108863)))

   notify-time-interval
   (integer(0:MAX))




5.3.1 notify-recipient-uri (uri)

   This attribute's value is a URL, which is a special case of a URI.
   Its value consists of a scheme and an address. The address specifies
   the Notification Recipient and the scheme specifies the Delivery
   Method for each Event Notification associated with this Subscription
   Object.


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   A Printer MUST support this attribute and return the value as
   supplied by the client (no case conversion or other canonicalization)
   in any operation response that includes this attribute.

   A client MUST supply this attribute in Subscription Creation
   Operation. Thus there is no need for a default Printer attribute.

   The URI scheme of the value of this attribute on a Subscription
   object MUST be a value of the "notify-schemes-supported (1setOf
   uriScheme)" Printer attribute.  Note: According to [RFC2396] the ":"
   terminates the scheme and so is not part of the scheme.  Therefore,
   values of the "notify-schemes-supported" Printer attribute do not
   include the ":" character.

   If the client supplies an unsupported scheme in the value of this
   attribute, then the Printer MUST NOT create the Subscription Object
   and MUST return the "notify-status-code" attribute with the 'client-
   error-uri-scheme-not-supported' value in the Subscription Attributes
   Group in the response.

   The Printer MUST treat the address part of this attribute as opaque.


5.3.2 notify-events (1setOf type2 keyword)

   This attribute contains a set of Subscribed Events.  When an Event
   occurs and it "matches" a value of this attribute, the Printer sends
   an Event Notification using information in the Subscription Object.
   The details of "matching" are described subsection 5.3.2.2.

   A Printer MUST support this attribute.

   A client MAY supply this attribute in a Subscription Creation
   Operation. If the client does not supply this attribute in
   Subscription Creation Operation, the Printer MUST populate this
   attribute on the Subscription Object with its "notify-events-default"
   attribute value.

   Each keyword value of this attribute on a Subscription Object MUST be
   a value of the  "notify-events-supported (1setOf type2 keyword)"
   Printer attribute.

   The number of values of this attribute MUST NOT exceed the value of
   the "notify-max-events-supported" attribute. A Printer MUST support
   at least 2 values per Subscription Object.  If the number of values
   supplied by a client in a Subscription Creation Operation exceeds the
   value of this attribute, the Printer MUST treat extra values as
   unsupported values and MUST use the value of 'successful-ok-too-many-

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   events' for the "notify-status-code" attribute in the Subscription
   Attributes Group of the response.


5.3.2.1 Standard Values for Subscribed Events

   Each value of this attribute is a keyword and it specifies a
   Subscribed Event that represents certain changes. Some keywords
   represent a subset of changes of another keyword, e.g., 'job-
   completed' is an Event value which is a sub-value of 'job-state-
   change'. See section 5.3.2.2 for the case where this attribute
   contains both a value and a sub-value.

   The values in this section are divided into three categories: No
   Events, Job Events and Printer Events.

   A Printer MUST support the Events indicated as "REQUIRED" and MAY
   support the Events indicated as "OPTIONAL".


5.3.2.1.1  No Events

   The standard and only keyword value for No Events is:

   'none':  REQUIRED - no Event Notifications for any Events. As the
      sole value of "notify-events-supported", this value means that the
      Printer does not support the sending of Event Notifications. As
      the sole value of "notify-events-default", this value means that a
      client MUST specify the "notify-events" attribute in order for a
      Subscription Creation Operation to succeed. If the Printer
      receives this value as the sole value of a Subscription Creation
      Operation, it does not create a Subscription Object. If a Printer
      receives this value with other values of a Subscription Creation
      Operation, the Printer MUST treat this value as an unsupported
      value.


5.3.2.1.2 Subscribed Printer Events

   The standard keyword values for Subscribed Printer Events are:

   'printer-state-changed':  REQUIRED - the Printer changed state from
      any state to any other state. Specifically, the value of the
      Printer's "printer-state", "printer-state-reasons" or "printer-is-
      accepting-jobs" attributes changed.

      This Subscribed Event value has the following sub-values:
      'printer-restarted' and 'printer-shutdown'. A client can listen

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      for any of these sub-values if it doesn't want to listen to all
      printer-state changes:

          'printer-restarted':  OPTIONAL - when the printer is powered
             up .

          'printer-shutdown':  OPTIONAL - when the device is being
             powered down .

          'printer-stopped:  REQUIRED - when the printer stops printing,
             i.e. the value of the "printer-state" Printer attribute
             becomes 'stopped'.

   'printer-config-changed':  OPTIONAL - when the configuration of a
      Printer has changed, i.e., the value of the "printer-message-from-
      operator" or any "configuration" Printer attribute has changed.  A
      "configuration" Printer attribute is an attribute which can change
      value because of some human interaction either direct or indirect,
      and which is not covered by one of the other Events in this
      section. Examples of "configuration" Printer attributes are any of
      the Job Template attributes, such as "xxx-supported", "xxx-ready"
      and "xxx-default". Often, such a change is the result of a client
      performing a Set-Printer-Attributes operation (see [ipp-set]) on
      the Printer. The client has to perform a Get-Printer-Attributes to
      find out the new values of these changed attributes.  This Event
      is useful for GUI clients and drivers to update the available
      printer capabilities to the user.

      This Event value has the following sub-values: 'printer-media-
      changed' and 'printer-finishings-changed'. A client can listen for
      any of these sub-values if it doesn't want to listen to all
      printer-configuration changes:

          'printer-media-changed':  OPTIONAL - when the media loaded on
             a printer has been changed, i.e., the "media-ready"
             attribute has changed.  This Event includes two cases: an
             input tray that goes empty and an input tray that receives
             additional media of the same type or of a different type.
             The client must check the "media-ready" Printer attribute
             (see [RFC2911] section 4.2.11) separately to find out what
             changed.

          'printer-finishings-changed':  OPTIONAL - when the finisher on
             a printer has been changed, i.e., the "finishings-ready"
             attribute has changed. This Event includes two cases: a
             finisher that goes empty and a finisher that is refilled
             (even if it is not full).  The client must check the


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             "finishings-ready" Printer attribute separately to find out
             what changed.

   'printer-queue-order-changed': OPTIONAL - the order of jobs in the
      Printer's queue has changed, so that an application that is
      monitoring the queue can perform a Get-Jobs operation to determine
      the new order.  This Event does not include when a job enters the
      queue (the 'job-created' Event covers that) and does not include
      when a job leaves the queue (the 'job-completed' Event covers
      that).


5.3.2.1.3 Subscribed Job Events

   The standard keyword values for Subscribed Job Events are:

   'job-state-changed':  REQUIRED - the job has changed from any state
      to any other state. Specifically, the Printer sends this Event
      whenever the value of the "job-state" attribute or "job-state-
      reasons" attribute changes. When a Job is removed from the Job
      Retention or Job History phases (see [RFC2911] section 4.3.7.1),
      no Event is generated.

      This Event value has the following sub-values: 'job-created',
      'job-completed' and 'job-stopped'. A client can listen for any of
      these sub-values if it doesn't want to listen to all 'job-state
      changes'.

          'job-created':  REQUIRED - the Printer has accepted a Job
             Creation operation, a Restart-Job operation [RFC2911], or
             any job operation that creates a Job object from an
             existing Job object.  The Printer sets the job's "time-at-
             creation" attribute value (see [RFC2911] section 4.3.14.1).
             The Printer puts the job in the 'pending', 'pending-held'
             or 'processing' states.

          'job-completed':  REQUIRED - the job has reached one of the
             completed states, i.e., the value of the job's "job-state"
             attribute has changed to: 'completed', 'aborted', or
             'canceled'. The Job's "time-at-completed" and "date-time-
             at-completed" (if supported) attributes are set (see
             [RFC2911] section 4.3.14).  When a Job completes, a
             Notification Recipient MAY query the Job using the Get-Job-
             Attributes operation.  To allow such a query, the Printer
             retains the Job in the Job Retention and/or the Job History
             phases (see [RFC2911] section 4.3.7.1) for a suitable
             amount of time that depends on implementation and the
             Delivery Methods supported.  The Printer also sends this

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             Event when a Job is removed with the Purge-Job operation
             (see [RFC2911] section 3.2.9).  In this case, the Event
             Notification MUST report the 'job-state' as 'canceled' and
             the Job object is no longer present for query.

          'job-stopped:  OPTIONAL - when the job stops printing, i.e.
             the value of the "job-state" Job attribute becomes
             'processing-stopped'.

   'job-config-changed':  OPTIONAL - when the configuration of a job has
      changed, i.e., the value of the "job-message-from-operator" or any
      of the "configuration" Job attributes have changed.  A
      "configuration" Job attribute is an attribute that can change
      value because of some human interaction either direct or indirect.
      Examples of "configuration" Job attributes are any of the job
      template attributes and the "job-name" attribute. Often, such a
      change is the result of the user or the Operator performing a Set-
      Job-Attributes operation (see [ipp-set]) on the Job object.  The
      client performs a Get-Job-Attributes to find out the new values of
      the changed attributes.  This Event is useful for GUI clients and
      drivers to update the job information to the user.

   'job-progress': OPTIONAL - when the Printer has completed Printing a
      sheet. See the separate [ipp-prog] specification for additional
      attributes that a Printer MAY send in an Event Notification caused
      by this Event. The "notify-time-interval" attribute affects this
      Event by causing the Printer NOT to send an Event Notification
      every time a 'job-progress' Events occurs. See section 5.3.8 for
      full details.


5.3.2.2 Rules for Matching of Subscribed Events

   When an Event occurs, the Printer MUST find each Subscription object
   whose "notify-events" attribute "matches" the Event.  The rules for
   "matching" of Subscribed Events are described separately for Printer
   Events and for Job Events. This section also describes some special
   cases.


5.3.2.2.1 Rules for Matching of Printer Events

   Suppose that the Printer causes Printer Event E to occur. For each
   Per-Job or Per-Printer Subscription S in the Printer, if E equals a
   value of this attribute in S or E is a sub-value of a value of this
   attribute in S, the Printer MUST generate an Event Notification.



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   Consider the example. There are three Subscription Objects each with
   the Subscribed Printer Event 'printer-state-changed'. Subscription
   Object A is a Per-Printer Subscription Object. Subscription Object B
   is a Per-Job Subscription Object for Job 1, and Subscription Object C
   is a Per-Job Subscription Object for Job 2. When the Printer enters
   the 'stopped' state, the Printer sends an Event Notification to the
   Notification Recipients of Subscription Objects A, B, and C because
   this is a Printer Event. Note if Job 1 has already completed, the
   Printer would not send an Event Notification for its Subscription
   Object, even if Job 1 is retained in the Job Retention and/or the Job
   History phases (see [RFC2911] section 4.3.7.1).


5.3.2.2.2 Rules for Matching of Job Events

   Suppose that Job J causes Job Event E to occur.

     1.For each Per-Printer Subscription S in the Printer, if E equals
       a value of this attribute in S or E is a sub-value of a value of
       this attribute in S, the Printer MUST generate an Event
       Notification.

     2.For each Per-Job Subscription S associated with Job J, if E
       equals a value of this attribute in S or E is a sub-value of a
       value of this attribute in S, the Printer MUST generate an Event
       Notification.

     3.For each Per-Job Subscription S that is NOT associated Job J, if
       E equals a value of this attribute in S or E is a sub-value of a
       value of this attribute in, the Printer MUST NOT generate an
       Event Notification from S.

   Consider the example: There are three Subscription Objects listening
   for the Job Event 'job-completed'.  Subscription Object A is a Per-
   Printer Subscription Object. Subscription Object B is a Per-Job
   Subscription Object for Job 1, and Subscription Object C is a Per-Job
   Subscription Object for Job 2. In addition, Per-Printer Subscription
   Object D is listening for the Job Event 'job-state-changed'. When Job
   1 completes, the Printer sends an Event Notification to the
   Notification Recipient of Subscription Object A (because it is Per-
   Printer) and Subscription Object B because it is a Per-Job
   Subscription Object associated with the Job generating the Event.
   The Printer also sends an Event Notification to the Notification
   Recipient of Subscription Object D because 'job-completed' is a sub-
   value of 'job-state-changed' - the value that Subscription Object D
   is listening for. The Printer does not send an Event Notification to
   the Notification Recipients of Subscription Object C because it is a


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   Per-Job Subscription Object associated with some Job other than the
   Job generating the Event.


5.3.2.2.3 Special Cases for Matching Rules

   This section contains rule for special cases.

   If an Event matches Subscribed Events in two different Subscription
   Objects and the Printer would send two identical Event Notifications
   (except for the "notify-subscription-id" attribute) to the same
   Notification Recipient using the same Delivery Method, the Printer
   MUST send both Event Notifications. That is, the Printer MUST NOT try
   to consolidate seemingly identical Event Notifications that occur in
   separate Subscription objects. Incidentally, the Printer MUST NOT
   reject Subscription Creation Operations that would create this
   scenario.

   If an Event matches two values of this "notify-events" attribute in a
   single Subscription object (e.g., a value and its sub-value), a
   Printer MAY send one Event Notification for each matched value in the
   Subscription Object or it MAY send only one Event Notification per
   Subscription Object. The rules in sections 5.3.2.2.1 and 5.3.2.2.2
   are purposefully ambiguous about the number of Event Notification
   sent when Event E matches two or more values in a Subscription
   Object.

   Consider the example: There are two Per-Printer Subscription Objects
   when a Job completes. Subscription Object A has the Subscribed Job
   Event 'job-state-changed'.  Subscription Object B has the Subscribed
   Job Events 'job-state-changed' and 'job-completed'. The Printer sends
   an Event Notification to the Notification Recipient of Subscription
   Object A with the value of  'job-state-changed' for the "notify-
   subscribing-event" attribute. The Printer sends either one or two
   Event Notifications to the Notification Recipient of Subscription
   Object B, depending on implementation. If it sends two Event
   Notifications, one has the value of  'job-state-changed' for the
   "notify-subscribing-event" attribute, and the other has the value of
   'job-completed' for the "notify-subscribing-event" attribute. If it
   sends one Event Notification, it has the value of either 'job-state-
   changed' or 'job-completed' for the "notify-subscribing-event"
   attribute, depending on implementation. The algorithm for choosing
   such a value is implementation dependent.






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5.3.3 notify-attributes (1setOf type2 keyword)

   This attribute contains a set of attribute names. When a Printer
   sends a Machine Consumable Event Notification, it includes a fixed
   set of attributes (see section 9.1).  If this attribute is present
   and the Event Notification is Machine Consumable, the Printer also
   includes the attributes specified by this attribute.

   A Printer MAY support this attribute.

   A client MAY supply this attribute in a Subscription Creation
   Operation.  If the client does not supply this attribute in
   Subscription Creation Operation or the Printer does not support this
   attribute, the Subscription Object either (1) MAY contain the
   "notify-attributes" attribute with a 'none' value or (2) NEED NOT
   contain the attribute at all.  There is no "notify-attributes-
   default" Printer attribute.

   Each keyword value of this attribute on a Subscription Object MUST be
   a value of the "notify-attributes-supported (1setOf type2 keyword)"
   Printer attribute.  The "notify-attributes-supported" MAY contain any
   Printer attribute, Job attribute or Subscription Object attribute
   that the Printer supports in an Event Notification.  It MUST NOT
   contain any of the attributes in Section 9.1 that a Printer
   automatically puts in an Event Notification; it would be redundant.
   If a client supplies an attribute in Section 9.1, the Printer MUST
   treat it as an unsupported attribute value of the "notify-attributes"
   attribute.

   The following rules apply to each keyword value N of the "notify-
   attributes" attribute: If the value N names:

   a)a Subscription attribute, the Printer MUST use the attribute N in
     the Subscription Object that is being used to generate the Event
     Notification.

   b)a Job attribute and the Printer is generating an Event
     Notification from a Per-Job Subscription Object S, the Printer
     MUST use the attribute N in the Job object associated with S.

   c)a Job attribute and the Printer is generating an Event
     Notification from a Per-Printer Subscription Object and the Event
     is:

       ?  a Job Event, the Printer MUST use the attribute N in the Job
          object that caused the Event.



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       ?  a Printer Event, the Printer MUST use the attribute N in the
          active Job.

   If a Printer supports this attribute and a Subscription Object
   contains this attribute and the Delivery Method generates a Machine
   Consumable Event Notification, the Printer MUST include in each Event
   Notification:

    a)the attributes specified in section 9.1 and

    b)each attribute named by this attribute.

   The Printer MUST NOT use this attribute to generate a Human
   Consumable Event Notification.


5.3.4 notify-user-data (octetString(63))

   This attribute contains opaque data that some Delivery Methods
   include in each Machine Consumable Event Notification. The opaque
   data might contain, for example:

      -  the identity of the Subscriber

      -  a path or index to some Subscriber information

      -  a key that identifies to the Notification Recipient the
         ultimate recipient of the Event Notification

      -  the id for a Notification Recipient that had previously
         registered with an Instant Messaging Service

   A Printer MUST support this attribute.

   A client MAY supply this attribute in a Subscription Creation
   Operation.  If the client does not supply this attribute in the
   Subscription Creation Operation, the Subscription Object either (1)
   MAY contain the "notify-user-data" attribute with a zero length value
   or (2) NEED NOT contain the attribute at all.  There is no "notify-
   user-data-default" Printer attribute.

   There is no "notify-user-data-supported" Printer attribute. Rather,
   any octetString whose length does not exceed 63 octets is a supported
   value.  If the length exceeds 63 octets, the Printer MUST treat it as
   an unsupported value.




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5.3.5 notify-charset (charset)

   This attribute specifies the charset to be used in the Event
   Notification content sent to the Notification Recipient, whether the
   Event Notification content is Machine Consumable or Human Consumable.

   A Printer MUST support this attribute.

   A client MAY supply this attribute in a Subscription Creation
   Operation. If the client does not supply this attribute in
   Subscription Creation Operation or supplies an unsupported value, the
   Printer MUST populate this attribute in the Subscription Object with
   the value of the "attributes-charset" operation attribute, which is a
   REQUIRED attribute in all IPP requests (see [RFC2911]). If the value
   of the "attributes-charset" attribute is unsupported, the Printer
   MUST populate this attribute in the Subscription Object with the
   value of the Printer's "charset-configured" attribute. There is no
   "notify-charset-default" Printer attribute.

   The value of this attribute on a Subscription Object MUST be a value
   of the "charset-supported (1setOf charset)" Printer attribute.


5.3.6 notify-natural-language (naturalLanguage)

   This attribute specifies the natural language to be used in any human
   consumable text in the Event Notification content sent to the
   Notification Recipient, whether the Event Notification content is
   Machine Consumable or Human Consumable.

   A Printer MUST support this attribute.

   A client MAY supply this attribute in a Subscription Creation
   Operation. If the client does not supply this attribute in
   Subscription Creation Operation or supplies an unsupported value, the
   Printer MUST populate this attribute in the Subscription Object with
   the value of the "attributes-natural-language" operation attribute,
   which is a REQUIRED attribute in all IPP requests (see [RFC2911]). If
   the value of the "attributes-natural-language" attribute is
   unsupported, the Printer MUST populate this attribute in the
   Subscription Object with the value of the Printer's "natural-
   language-configured" attribute. There is no "notify-natural-language-
   default" Printer attribute.

   The value of this attribute on a Subscription Object MUST be a value
   of the "generated-natural-language-supported (1setOf type2
   naturalLanguage)" Printer attribute.


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5.3.7 notify-lease-duration (integer(0:67108863))

   This attribute specifies the duration of the lease (in seconds)
   associated with the Per-Printer Subscription Object at the time the
   Subscription Object was created or the lease was renewed. The
   duration of the lease is infinite if the value is 0, i.e., the lease
   never expires.  See section 5.4.3 on "notify-lease-expiration-time
   (integer(0:MAX))" for more details.

   This attribute is not present on a Per-Job Subscription Object
   because the Subscription Object lasts exactly as long as the
   associated Job object.  See discussion of the 'job-completed' event
   in section 5.3.2.1.3 about retention of the Job object after
   completion.

   A Printer MUST support this attribute.

   For a Subscription Object Creation operation of a Per-Job
   Subscription Object, the client MUST NOT supply this attribute. If
   the client does supply this attribute, the Printer MUST treat it as
   an unsupported attribute.

   For a Subscription Creation Operation of a Per-Printer Subscription
   Object or a Renew-Subscription operation, a client MAY supply this
   attribute. If the client does not supply this attribute, the Printer
   MUST populate this attribute with its "notify-lease-duration-default"
   (0:67108863) attribute value. If the client supplies this attribute
   with an unsupported value, the Printer MUST populate this attribute
   with a supported value, and this value SHOULD be as close as possible
   to the value requested by the client. Note: this rule implies that a
   Printer doesn't assign the value of 0 (infinite) unless the client
   requests it.

   After the Printer has populated this attribute with a supported
   value, the value represents the "granted duration" of the lease in
   seconds and the Printer sets the value of the Subscription Object's
   "notify-lease-expiration-time" attribute as specified in section
   5.4.3.

   The value of this attribute on a Subscription Object MUST be a value
   of the "notify-lease-duration-supported" (1setOf (integer(0:67108863)
   | rangeOfInteger(0:67108863))) Printer attribute.

   A Printer MAY require authentication in order to return the value of
   0 (the lease never expires) as one of the values of "notify-lease-
   duration-supported", and to allow 0 as a value of the "notify-lease-
   duration" attribute.


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   Note:  The maximum value 67,108,863 is 2 raised to the 26 power minus
   1 and is about 2 years in seconds.  The value is considerably less
   than MAX so that there is virtually no chance of an overflow when it
   is added to "printer-up-time" to produce "notify-lease-expiration-
   time".


5.3.8 notify-time-interval (integer(0:MAX))

   The 'job-progress' Event occurs each time that a Printer completes a
   sheet.  Some Notification Recipients  do not want to receive an Event
   Notification every time this Event occurs. This attribute allows a
   Subscribing Client to request how often it wants to receive Event
   Notifications for 'job-progress' Events. The value of this attribute
   MAY be any nonnegative integer (0,MAX) indicating the minimum number
   of seconds between 'job-progress' Event Notifications.

   The Printer MUST support this attribute if and only if the Printer
   supports the 'job-progress' Event.

   A client MAY supply this attribute in a Subscription Creation
   Operation.  If the client does not supply this attribute in the
   Subscription Creation Operation, the Subscription Object either (1)
   MAY contain the "notify-time-interval" attribute with a '0' value or
   (2) NEED NOT contain this attribute at all.   There is no "notify-
   time-interval-default" Printer attribute.

   There is no "notify-time-interval-supported" Printer attribute.

   If the 'job-progress' Event occurs and a Subscription Object contains
   the 'job-progress' Event as a value of the 'notify-events' attribute,
   there are two cases to consider:

   1.This attribute is not present on the Subscription Object or has
     the value of 0. The Printer MUST generate and send an Event
     Notification (as is the case with other Events).

   2.This attribute is present with a nonzero value of N:

     a)If the Printer has not sent an Event Notification for the 'job-
       progress' Event for the associated Subscription Object within
       the past N seconds, the Printer MUST send an Event Notification
       for the Event that just occurred. Note when the Printer
       completes the first page of a Job, this rule implies that the
       Printer sends an Event Notification for a Per-Job Subscription
       Object.



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     b)Otherwise, the Printer MUST NOT generate or send an Event
       Notification for the associated Subscription Object. The Printer
       MUST NOT increase the value of the "notify-sequence-number"
       Subscription Object attribute (i.e., the sequence of values of
       the "notify-sequence-number" attribute counts the Event
       Notifications that the Printer sent and not the Events that do
       not cause an Event Notification to be sent).

   It is RECOMMENDED that a Subscribing Client use this attribute when
   it subscribes to the 'job-progress' Event, and that the value be
   sufficiently large to limit the frequency with which the Printer
   sends Event Notifications requests.

   This attribute MUST NOT effect any Events other than 'job-progress'.


5.4 Subscription Description Attributes

   Subscription Description Attributes are those attributes that a
   Printer adds to a Subscription Object at the time of its creation.

   A Printer MUST support all attributes in this Table 2.

   A client MUST NOT supply the attributes in Table 2 in a Subscription
   Template Attributes Group of a Subscription Creation Operation. If
   the client supplies them, the Printer MUST NOT set them and MUST
   treat them as unsupported attributes. There are no corresponding
   default or supported attributes.





















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               Table 2 - Subscription Description Attributes


       Subscription Object attributes:


       notify-subscription-id (integer(1:MAX))

       notify-sequence-number (integer(0:MAX))

       notify-lease-expiration-time (integer(0:MAX))

       notify-printer-up-time (integer(1:MAX))

       notify-printer-uri (uri)

       notify-job-id (integer(1:MAX))

       notify-subscriber-user-name (name(MAX))




5.4.1 notify-subscription-id  (integer (1:MAX))

   This attribute identifies a Subscription Object instance with a
   number that is unique within the context of the Printer. The Printer
   generates this value at the time it creates the Subscription Object.

   A Printer MUST support this attribute.

   The Printer MAY assign the value of this attribute sequentially as it
   creates Subscription Objects.  However, if there is no security on
   Subscription objects, sequential assignment exposes the system to a
   passive traffic monitoring threat.

   The Printer SHOULD avoid re-using recent values of this attribute
   during continuous operation of the Printer as well as across power
   cycles. Then a Subscribing Client is unlikely to find that a stale
   reference accesses a new Subscription Object.

   The 0 value is not permitted in order to allow for compatibility with
   "job-id" and with SNMP index values, which also cannot be 0.






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5.4.2 notify-sequence-number (integer (0:MAX))

   The value of this attribute indicates the number of times that the
   Printer has generated and attempted to send an Event Notification for
   this Subscription object. When an Event Notification contains this
   attribute, the Notification Recipient can determine whether it missed
   some Event Notifications (i.e., numbers skipped) or received
   duplicates (i.e., same number twice).

   A Printer MUST support this attribute.

   When the Printer creates a Subscription Object, it MUST set the value
   of this attribute to 0. This value indicates that the Printer has not
   sent any Event Notifications for this Subscription Object.

   Each time the Printer sends a newly generated Event Notification, it
   MUST increase the value of this attribute by 1. For some Delivery
   Methods, the Printer MUST include this attribute in each Event
   Notification, and the value MUST be the value after it is increased
   by 1. That is, the value of this attribute in the first Event
   Notification after Subscription object creation MUST be 1, the second
   MUST be 2, etc.  If a Delivery Method is defined such that the
   Notification Recipient returns a response, the Printer can re-try
   sending an Event Notification a certain number of times with the same
   sequence number when the Notification Recipient fails to return a
   response.

   If a Subscription Object lasts long enough to reach the value of MAX,
   its next value MUST be 0, i.e., it wraps.


5.4.3 notify-lease-expiration-time (integer(0:MAX))

   This attribute specifies the time in the future when the lease on the
   Per-Printer Subscription Object will expire, i.e. the "printer-up-
   time" value at which the lease will expire. If the value is 0, the
   lease never expires.

   A Printer MUST support this attribute.

   When the Printer creates a Per-Job Subscription Object, this
   attribute MUST NOT be present - the Subscription Object lasts exactly
   as long as the associated Job object.  See also the discussion of the
   'job-completed' event in section 5.3.2.1.3 about retention of the Job
   object after completion so that a Notification Recipient can query
   the Job object after receiving the 'job-completed' Event
   Notification.


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   When the Printer creates a Per-Printer Subscription Object, it
   populates this attribute with a value that is the sum of the values
   of the Printer's "printer-up-time" attribute and the Subscription
   Object's "notify-lease-duration" attribute with the following
   exception. If the value of the Subscription Object's "notify-lease-
   duration" attribute is 0 (i.e., no expiration time), then the value
   of this attribute MUST be set to 0 (i.e., no expiration time).

   When the Printer powers up, it MUST set the value of this attribute
   in each persistent Subscription Object using the algorithm in the
   previous paragraph.

   When the "printer-up-time" equals the value of this attribute, the
   Printer MUST delete the Subscription Object. A client can extend a
   lease of a Per-Printer Subscription Object with the Renew-
   Subscription operation (see section 11.2.6).

   Note: In order to compute the number of seconds remaining in a lease
   for a Per-Printer Subscription Object, a client can subtract the
   Subscription's "notify-printer-up-time" attribute (see section 5.4.4)
   from the Subscription's "notify-lease-expiration-time" attribute.


5.4.4 notify-printer-up-time (integer(1:MAX))

   This attribute is an alias for the Printer's "printer-up-time"
   attribute " (see [RFC2911] section 4.4.29).  In other words, when
   this attribute is queried with the Get-Subscriptions or Get-
   Subscription-Attributes operations (see sections 11.2.4 and 11.2.5),
   the value returned is the current value of the Printer's "printer-up-
   time" attribute, rather than the time at which the Subscription
   Object was created.

   A Printer MUST support this attribute.

   When the Printer creates a Per-Job Subscription Object, this
   attribute MUST NOT be present. When the Printer creates a Per-Printer
   Subscription Object, this attribute MUST be present.

   Note: this attribute exists in a Per-Printer Subscription Object so
   that a client using the Get-Subscription-Attributes or Get-
   Subscription operations can convert the Per-Printer Subscription's
   "notify-lease-expiration-time" attribute to wall clock time with one
   request. If the value of the "notify-lease-expiration-time" attribute
   is not 0 (i.e., no expiration time), then the difference between the
   "notify-lease-expiration-time" attribute and the "notify-printer-up-
   time" is the remaining number of seconds on the lease from the
   current time.

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5.4.5 notify-printer-uri (uri)

   This attribute identifies the Printer object that created this
   Subscription Object.

   A Printer MUST support this attribute.

   During a Subscription Creation Operation, the Printer MUST populate
   this attribute with the value of the "printer-uri" operation
   attribute in the request.  From the Printer URI, the client can, for
   example, determine what security scheme was used.


5.4.6 notify-job-id (integer(1:MAX))

   This attribute specifies whether the containing Subscription Object
   is a Per-Job or Per-Printer Subscription Object, and for Per-Job
   Subscription Objects, it specifies the associated Job.

   A Printer MUST support this attribute.

   If this attribute is not present, the Subscription Object MUST be a
   Per-Printer Subscription. If this attribute is present, the
   Subscription Object MUST be a Per-Job Subscription Object and this
   attribute MUST identify the Job with which the Subscription Object is
   associated.

   Note: This attribute could be useful to a Notification Recipient that
   receives an Event Notification generated from a Per-Job Subscription
   Object and caused by a Printer Event. The Event Notification gives
   access to the Printer and the Subscription Object. The Event
   Notification gives access to the associated Job only via this
   attribute.  See discussion of the 'job-completed' event in section
   5.3.2.1.3 about retention of the Job object after completion so that
   a Notification Recipient can query the Job object after receiving the
   'job-completed' Event Notification.


5.4.7 notify-subscriber-user-name (name(MAX))

   This attribute contains the name of the user who performed the
   Subscription Creation Operation.

   A Printer MUST support this attribute.

   The Printer sets this attribute to the most authenticated printable
   name that it can obtain from the authentication service over which
   the Subscription Creation Operation was received. The Printer uses

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   the same mechanism for determining the value of this attribute as it
   does for a Job's "job-originating-user-name" (see [RFC2911] section
   4.3.6).

   Note:  To help with authentication, a Subscription Object may have
   additional private attributes about the user, e.g., a credential of a
   principal. Such private attributes are implementation-dependent and
   not defined in this document.


6 Printer Description Attributes Related to Notification

   This section defines the Printer Description attributes that are
   related to Notification. Table 3 lists the Printer Description
   attributes, indicates the Printer support required for conformance,
   and whether or not the attribute is READ-ONLY (see section 3.1):


   Table 3 - Printer Description Attributes Associated with Notification


   Printer object attributes:                   REQUIRED      READ-ONLY


   printer-state-change-time (integer(1:MAX))   No            Yes

   printer-state-change-date-time (dateTime)    No            Yes




6.1 printer-state-change-time (integer(1:MAX))

   This OPTIONAL attribute records the most recent time at which the
   'printer-state-changed' Printer Event occurred whether or not any
   Subscription objects were listening for this event.  This attribute
   helps a client or operator to determine how long the Printer has been
   in its current state.

   A Printer MAY support this attribute and if so, the attribute MUST be
   READ-ONLY.

   On power-up, the Printer MUST set the value of this attribute to be
   the value of its "printer-up-time" attribute, so that it always has a
   value. Whenever the 'printer-state-changed' Printer Event occurs, the
   Printer MUST set this attribute to the value of the Printer's
   "printer-up-time" attribute.


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6.2 printer-state-change-date-time (dateTime)

   This OPTIONAL attribute records the most recent time at which the
   'printer-state-changed' Printer Event occurred whether or not there
   were any Subscription Objects listening for this event.  This
   attribute helps a client or operator to determine how long the
   Printer has been in its current state.

   A Printer MAY support this attribute and if so, the attribute MUST be
   READ-ONLY.

   On power-up, the Printer MUST set the value of this attribute to be
   the value of its "printer-current-time" attribute, so that it always
   has a value (see [RFC2911] section 4.4.30 on "printer-current-time").
   Whenever the 'printer-state-changed' Printer Event occurs, the
   Printer MUST set this attribute to the value of the Printer's
   "printer-current-time" attribute.


7 New Values for Existing Printer Description Attributes

   This section contains those attributes for which additional values
   are added.


7.1 operations-supported (1setOf type2 enum)

   The following "operation-id" values are added in order to support the
   new operations defined in this document:




















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                    Table 4 - Operation-id assignments


     Value        Operation Name


     0x0016       Create-Printer-Subscriptions

     0x0017       Create-Job-Subscriptions

     0x0018       Get-Subscription-Attributes

     0x0019       Get-Subscriptions

     0x001A       Renew-Subscription

     0x001B       Cancel-Subscription


8 Attributes Only in Event Notifications

   This section contains those attributes that exist only in Event
   Notifications and do not exist in any objects.


8.1 notify-subscribed-event (type2 keyword)

   This attribute indicates the Subscribed Event that caused the Printer
   to send this Event Notification. This attribute exists only in Event
   Notifications.

   This attribute MUST contain one of the values of the "notify-events"
   attribute in the Subscription Object, i.e., one of the Subscribed
   Event values. Its value is the Subscribed Event that "matches" the
   Event that caused the Printer to send this Event Notification. This
   Subscribed Event value may be identical to the Event or the Event may
   be a sub-value of the Subscribed Event. For example, the 'job-
   completed' Event (which is a sub-event of the 'job-state-changed'
   event) would cause the Printer to send an Event Notification for
   either the 'job-completed' or 'job-state-changed' Subscribed Events
   and to send the 'job-completed' or 'job-state-changed' value for this
   attribute, respectively,.  See section 5.3.2.2 for the "matching"
   rules of Subscribed Events and for additional examples.

   The Delivery Method Document specifies whether the Printer includes
   the value of this attribute in an Event Notification.



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8.2 notify-text (text(MAX))

   This attribute contains a Human Consumable text message (see section
   9.2). This message describes the Event and is encoded as plain text,
   i.e., 'text/plain' with the charset specified by Subscription
   Object's "notify-charset" attribute.

   The Delivery Method Document specifies whether the Printer includes
   this attribute in an Event Notification.


9 Event Notification Content

   This section defines the Event Notification content that the Printer
   sends when an Event occurs.

   When an Event occurs, the Printer MUST find each Subscription object
   whose "notify-events" attribute "matches" the Event. See section
   5.3.2.2 for details on "matching". For each matched Subscription
   Object, the Printer MUST create an Event Notification with the
   content and format that the Delivery Method Document specifies. The
   content contains the value of attributes specified by the Delivery
   Method Document. The Printer obtains the values immediately after the
   Event occurs. For example, if the "printer-state" attribute changes
   from 'idle' to 'processing', the Event 'printer-state-changed' occurs
   and the Printer puts various attributes into the Event Notification,
   including "printer-up-time" and "printer-state" with the values that
   they have immediately after the Event occurs, i.e., the value of
   "printer-state" is 'processing'.

   Event Notification Ordering:

   When a Printer sends Event Notifications, the Event Notifications
   from any given Subscription Object MUST be in time stamp order, i.e.,
   in order of increasing "printer-up-time" attribute value in the Event
   Notification (see Table 5).  These Event Notifications MAY be
   interleaved with those from other Subscription Objects, as long as
   those others are also in time stamp order.  The Printer MUST observe
   these ordering requirements whether sending multiple pending Events
   as multiple separate Event Notifications or together in a single
   Compound Event Notification.

   If a Subscribing Client wants the Printer to send certain Event
   Notifications in time stamp order, the Subscribing Client uses a
   single Subscription Object.  Even so, depending on the underlying
   transport, the actual order that a Notification Recipient receives
   separate Event Notifications may differ from the order sent by the
   Printer (e.g., email).

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   Example:  Consider two Per-Printer Subscription Objects: SO1 and SO2.
   SO1 requests 'job-state-changed' events and SO2 requests 'printer-
   state-changed' events.  The number in parens is the time stamp.  The
   following Event Notification sequences are the only ones that conform
   to the ordering requirements for the Printer to send the Event
   Notifications:

   (a) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO1: 'job-
   completed' (1009), SO2: 'printer-stopped' (1005)

   (b) SO1: 'job-created' (1000), SO1: 'job-stopped' (1005), SO2:
   'printer-stopped' (1005), SO1: 'job-completed' (1009)

   (c) SO1: 'job-created' (1000), SO2: 'printer-stopped' (1005), SO1:
   'job-stopped' (1005), SO1: 'job-completed' (1009)

   (d) SO2: 'printer-stopped (1005), SO1: 'job-created' (1000), SO1:
   'job-stopped' (1005), SO1: 'job-completed' (1009)

   Examples (b) and (c) are interleaved; examples (a) and (d) are not
   interleaved and are not appropriate for some Delivery Methods.

   If two different Events occur simultaneously, or nearly so (e.g.,
   "printer-up-time" has the same value for both), the Printer MUST
   create a separate Event Notification for each Event, even if the
   associated Subscription Object is the same for both Events. However,
   the Printer MAY combine these distinct Event Notifications into a
   single Compound Event Notification if the Delivery Method supports
   Compound Event Notifications.  For example, suppose that two nearly-
   simultaneously Events represent two successive 'printer-state-
   changed' Events, one from 'idle' to 'processing' and another from
   'processing' to 'stopped'. These two Events have the same name but
   are different instances of the Event. Then the Printer MUST create a
   separate Event Notification for each Event and SHOULD accurately
   report the "printer-state" of the first Event as 'processing' and the
   second Event as 'stopped'.

   If a Subscription Object contains more than one Subscribed Event, and
   several Events occur in quick succession each matching a different
   Subscribed Event in the Subscription Object, the Printer MUST NOT
   generate a single Event Notification from several of these Events,
   but MAY combine distinct Event Notifications into a single Compound
   Event Notification if the Delivery Method supports Compound Event
   Notifications.

   After the Printer has created the Event Notification, the Printer
   delivers it via either a:


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       Push Delivery Method: The Printer sends the Event Notification
       shortly after an Event occurs. For some Push Delivery Methods,
       the Notification Recipient MUST send a response; for others it
       MUST NOT send a response.

       Pull Delivery Method: The Printer saves Event Notifications for
       some event-lease time and expects the Notification Recipient to
       request Event Notifications. The Printer returns the Event
       Notifications in a response to such a request.

   If an error that meets the following conditions occurs, the Printer
   MUST cancel the Subscription Object.

   a)the error occurs during the sending of an Event Notification
     generated from Subscription Object S  AND

   b)the error would continue to occur every time the Printer sends an
     Event Notification generated from Subscription Object S in the
     future.

   For example, if the address of the "notify-recipient-uri" of
   Subscription Object A references a non-existent target and the
   Printer determines this fact, it MUST delete Subscription Object A.

   The next two sections describe the values that a Printer sends in the
   content of Machine Consumable and Human Consumable Event
   Notifications, respectively.

   The tables in the sub-sections of this section contain the following
   columns:

     a)Source Value: the name of the attribute that supplies the value
       for the Event Notification. Asterisks in this field refer to a
       note below the table.

     b)Sends: if the Printer supports the value (column 1) on the
       Source Object (column 3) the Delivery Method MUST specify:

          MUST: that the Printer MUST send the value.

          SHOULD: either that the Printer MUST send the value or that
          the value is incompatible with the Delivery Method.

          MAY: that the Printer MUST, SHOULD, MAY, MUST NOT, SHOULD NOT,
          or NEED NOT send the value. The Delivery Method specifies the
          level of conformance for the Printer.



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     c)Source Object: the object from which the source value comes. If
       the object is "Event Notification", the Printer fabricates the
       value when it sends the Event Notification. See section 8.


9.1 Content of Machine Consumable Event Notifications

   This section defines the attributes that a Delivery Method MUST
   mention in a Delivery Method Document when specifying the Machine
   Consumable Event Notification's contents.

   This document does not define the order of attributes in Event
   Notifications.  However, Delivery Method Documents MAY define the
   order of some or all of the attributes.

   A Delivery Method Document MUST specify additional attributes (if
   any) that a Printer implementation sends in a Machine Consumable
   Event Notification.

   Notification Recipients MUST be able to accept Event Notifications
   containing attributes they do not recognize.  What a Notification
   Recipient does with an unrecognized attribute is implementation-
   dependent.  Notification Recipients MAY attempt to display
   unrecognized attributes anyway or MAY ignore them.

   The next three sections define the attributes in Event Notification
   Contents that are:

     1.for all Events

     2.for Job Events only

     3.for Printer Events only


9.1.1 Event Notification Content Common to All Events

   This section lists the attributes that a Delivery Method Document
   MUST specify for all Events.

   Table 5 lists potential values in each Event Notification.








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            Table 5 - Attributes in Event Notification Content


   Source Value                               Sends      Source Object


   notify-subscription-id (integer(1:MAX))    MUST       Subscription

   notify-printer-uri (uri)                   MUST       Subscription

   notify-subscribed-event (type2 keyword)    MUST       Event
                                                         Notification

   printer-up-time (integer(MIN:MAX))         MUST       Printer

   printer-current-time (dateTime) *          MUST       Printer

   notify-sequence-number (integer (0:MAX))   SHOULD     Subscription

   notify-charset (charset)                   SHOULD     Subscription

   notify-natural-language (naturalLanguage)  SHOULD     Subscription

   notify-user-data (octetString(63)) **      SHOULD     Subscription

   notify-text (text)                         SHOULD     Event
                                                         Notification

   attributes from the "notify-attributes"    MAY        Printer
   attribute ***

   attributes from the "notify-attributes"    MAY        Job
   attribute ***

   attributes from the "notify-attributes"    MAY        Subscription
   attribute ***


   *A Printer MUST send this value only if and only if it supports the
   Printer's "printer-current-time" attribute.

   ** If the Subscription Object does not contain a "notify-user-data"
   attribute and the Delivery Method Document REQUIRES the Printer to
   send the "notify-user-data" source value in the Event Notification,
   the Printer MUST send an octet-string of length 0.

   *** The last three rows represent additional attributes that a client
   MAY request via the  "notify-attributes" attribute. A Printer MAY

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   support the "notify-attributes" attribute. The Delivery Method MUST
   say that the Printer MUST, SHOULD, MAY, MUST NOT, SHOULD NOT, or NEED
   NOT support the "notify-attributes" attribute and specific values of
   this attribute. The Delivery Method MAY say that support for the
   "notify-attributes" is conditioned on support of the attribute by the
   Printer or it MAY say that Printer MUST support the "notify-
   attributes" attribute if the Printer supports the Delivery Method.


9.1.2 Additional Event Notification Content for Job Events

   This section lists the additional attributes that a Delivery Method
   Document MUST specify for Job Events.  See Table 6.


      Table 6 - Additional Event Notification Content for Job Events


   Source Value                                  Sends   Source Object


   job-id (integer(1:MAX))                       MUST    Job

   job-state (type1 enum)                        MUST    Job

   job-state-reasons (1setOf type2 keyword)      MUST    Job

   job-impressions-completed (integer(0:MAX)) *  MUST    Job


   *  The Printer MUST send the "job-impressions-completed" attribute in
   an Event Notification only for the combinations of Events and
   Subscribed Events shown in Table 7.
















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     Table 7 - Combinations of Events and Subscribed Events for "job-
                          impressions-completed"


   Job Event               Subscribed Job Event


   'job-progress'          'job-progress'

   'job-completed'         'job-completed'

   'job-completed'         'job-state-changed'




9.1.3 Additional Event Notification Content for Printer Events

   This section lists the additional attributes that a Delivery Method
   Document MUST specify for Printer Events. See Table 8.


    Table 8 - Additional Event Notification Content for Printer Events


   Source Value                                   Sends  Source Object


   printer-state (type1 enum)                     MUST   Printer

   printer-state-reasons (1setOf type2 keyword)   MUST   Printer

   printer-is-accepting-jobs (boolean)            MUST   Printer



9.2 Content of Human Consumable Event Notification

   This section defines the information that a Delivery Method MUST
   mention in a Delivery Method Document when specifying the Human
   Consumable Event Notifications contents or the value of the "notify-
   text" attribute.

   Such a Delivery Method MUST specify the following information and a
   Printer SHOULD send it:

     a)the Printer name (see Table 9)


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     b)the time of the Event (see Table 11)
     c)for Printer Events only:
       i)   the Event (see Table 10) and/or Printer state information
       (see Table 14)
     d)for Job Events only:
       i) the job identity (see Table 12)
       ii)  the Event (see Table 10) and/or Job state information (see
            Table 13)

   The subsections of this section specify the attributes that a Printer
   MUST use to obtain this information.

   A Delivery Method Document MUST specify additional information (if
   any) that a Printer implementation sends in a Human Consumable Event
   Notification or in the "notify-text" attribute.

   A client MUST NOT request additional attributes via the "notify-
   attributes" attribute because this attribute works only for Machine
   Consumable Event Notifications.

   Notification Recipients MUST NOT expect to be able to parse the Human
   Consumable Event Notification contents or the value of the "notify-
   text" attribute.

   The next three sections define the attributes in Event Notification
   Contents that are:

       a) for all Events
       b) for Job Events only
       c) for Printer Events only


9.2.1 Event Notification Content Common to All Events

   This section lists the source of the information that a Delivery
   Method MUST specify for all Events.

   There is a separate table for each piece of information. Each row in
   the table represents a source value for the information and the
   values are listed in order of preference, with the first one being
   the preferred one. An implementation SHOULD use the source value from
   the earliest row in each table. It MAY use the source value from
   another row instead, or it MAY combine the source values from several
   rows. An implementation is free to determine the best way to present
   this information.

   In all tables of this section, all rows contain a "MAY" in order to
   state that the Delivery Method specifies the conformance.

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   Table 9 lists the source of the information for the Printer Name. The
   "printer-name" is more user-friendly unless the Notification
   Recipient is in a place where the Printer name is not meaningful. For
   example, an implementation could have the intelligence to send the
   value of the "printer-name" attribute to a Notification Recipient
   that can access the Printer via value of the "printer-name" attribute
   and otherwise send the value of the "notify-printer-uri" attribute.


           Table 9 - Printer Name in Event Notification Content


   Source Value                            Sends       Source Object


   printer-name (name(127))                MAY         Printer

   notify-printer-uri (uri)                MAY         Subscription




   Table 10 lists the source of the information for the Event name. A
   Printer MAY combine this information with state information described
   for Jobs in Table 13 or for Printers in Table 14.


            Table 10 - Event Name in Event Notification Content


   Source Value                               Sends    Source Object


   notify-subscribed-event (type2 keyword)    MAY      Subscription



   Table 11 lists the source of the information for the time that the
   Event occurred. A Printer can send this value only if it supports the
   Printer's "printer-current-time" attribute. If a Printer does not
   support the "printer-current-time" attribute, it MUST NOT send the
   "printer-up-time" value instead, since it is not an allowed option
   for human consumable information.






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            Table 11 - Event Time in Event Notification Content


   Source Value                               Sends    Source Object


   printer-current-time (dateTime)            MAY      Printer




9.2.2 Additional Event Notification Content for Job Events

   This section lists the source of the additional information that a
   Delivery Method MUST specify for Job Events.

   Table 12 lists the source of the information for the job name. The
   "job-name" is likely more meaningful to a user than "job-id".


             Table 12 - Job Name in Event Notification Content


   Source Value                               Sends    Source Object


   job-name (name(MAX))                       MAY      Job

   job-id (integer(1:MAX))                    MAY      Job



   Table 13 lists the source of the information for the job state. If a
   Printer supports the "job-state-message" and "job-detailed-state-
   message" attributes, it SHOULD use those attributes for the job state
   information, otherwise, it should fabricate such information from the
   "job-state" and "job-state-reasons". For some Events, a Printer MAY
   combine this information with Event information.











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            Table 13 - Job State in Event Notification Content


   Source Value                                      Sends    Source
                                                              Object


   job-state-message (text(MAX))                     MAY      Job

   job-detailed-status-messages (1setOf text(MAX))   MAY      Job

   job-state (type1 enum)                            MAY      Job

   job-state-reasons (1setOf type2 keyword)          MAY      Job



9.2.3 Additional Event Notification Content for Printer Events

   This section lists the source of the additional information that a
   Delivery Method MUST specify for Printer Events.

   Table 14 lists the source of the information for the printer state.
   If a Printer supports the "printer-state-message", it SHOULD use that
   attribute for the job state information, otherwise it SHOULD
   fabricate such information from the "printer-state" and "printer-
   state-reasons". For some Events, a Printer MAY combine this
   information with Event information.





















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          Table 14 - Printer State in Event Notification Content


   Source Value                                      Sends    Source
                                                              Object


   printer-state-message (text(MAX))                 MAY      Printer

   printer-state (type1 enum)                        MAY      Printer

   printer-state-reasons (1setOf type2 keyword)      MAY      Printer

   printer-is-accepting-jobs (boolean)               MAY      Printer


10 Delivery Methods

   A Delivery Method is the mechanism, i.e., protocol, by which the
   Printer delivers an Event Notification to a Notification Recipient.
   There are several potential Delivery Methods for Event Notifications,
   standardized, as well as proprietary.  This document does not define
   any of these delivery mechanisms.  Each Delivery Method MUST be
   defined in a Delivery Method Document that is separate from this
   document. New Delivery Methods will be created as needed using an
   extension to the registration procedures defined in [RFC2911].  Such
   documents are registered with IANA (see section 13.7.3).

   The following sorts of Delivery Methods are expected:

     - The Notification Recipient polls for Event Notifications at
     intervals directed by the Printer

     - The Printer sends Event Notifications to the Notification
     Recipient using http as the transport.

     - The Printer sends an email message.

   This section specifies how to define a Delivery Method Document and
   what to put in such a document.

   A Delivery Method Document MUST contain an exact copy of the
   following paragraph, caption and table. In addition, column 2 of the
   table in the Delivery Method Document MUST contain answers to
   questions in column 1 for the Delivery Method. Also, the Delivery
   Method document MUST contain a reference to this document and call
   that reference [ipp-ntfy] because the table contains an [ipp-ntfy]
   reference.

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   If a Printer supports this Delivery Method, the following are its
   characteristics.


             Table 15 - Information about the Delivery Method


   Document Method Conformance Requirement     Delivery Method
                                               Realization


   1.What is the URL scheme name for the
     Delivery Method?

   2.Is the Delivery Method REQUIRED,
     RECOMMENDED, or OPTIONAL for an IPP
     Printer to support?

   3.What transport and delivery protocols
     does the Printer use to deliver the
     Event Notification Content, i.e., what
     is the entire network stack?

   4.Can several Event Notifications be
     combined into a Compound Event
     Notification?

   5.Is the Delivery Method initiated by the
     Notification Recipient (pull), or by the
     Printer (push)?

   6.Is the Event Notification content
     Machine Consumable or Human Consumable?

   7.What section in this document answers
     the following question? For a Machine
     Consumable Event Notification, what is
     the representation and encoding of
     values defined in section 9.1 of [ipp-
     ntfy] and the conformance requirements
     thereof? For a Human Consumable Event
     Notification, what is the representation
     and encoding of pieces of information
     defined in section 9.2 of [ipp-ntfy] and
     the conformance requirements thereof?

   8.What are the latency and reliability of
     the transport and delivery protocol?

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     the transport and delivery protocol?

   9.What are the security aspects of the
     transport and delivery protocol, e.g.,
     how it is handled in firewalls?

   10.  What are the content length
     restrictions?

   11.  What are the additional values or
     pieces of information that a Printer
     sends in an Event Notification content
     and the conformance requirements
     thereof?

   12.  What are the additional Subscription
     Template and/or Subscription Description
     attributes and the conformance
     requirements thereof?

   13.  What are the additional Printer
     Description attributes and the
     conformance requirements thereof?



11 Operations for Notification

   This section defines all of the operations for Notification. Section
   7.1 assigns the "operation-id" for each operation.  The following two
   sub-sections define Subscription Creation Operations, and other
   operations.


11.1 Subscription Creation Operations

   This section defines the Subscription Creation Operations. The first
   section on Create-Job-Subscriptions gives most of the information.
   The other Subscription Creation Operations refer to the section on
   Create-Job-Subscriptions, even though the Create-Job-Subscriptions
   operation is the only OPTIONAL operation in this document (see
   section 12).

   A Printer MUST support Create-Printer-Subscriptions and the
   Subscription Template Attributes Group in Job Creation operations. It
   MAY support Create-Job-Subscriptions operations.


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11.1.1 Create-Job-Subscriptions Operation

   The operation creates one or more Per-Job Subscription Objects.  The
   client supplies one or more Subscription Template Attributes Groups
   each containing one or more of Subscription Template Attributes
   (defined in section 5.3).

   Except for errors, the Printer MUST create exactly one Per-Job
   Subscription Object from each Subscription Template Attributes Group
   in the request, even if the newly created Subscription Object would
   have identical behavior to some existing Subscription Object. The
   Printer MUST associate each newly created Per-Job Subscription Object
   with the target Job, which is specified by the "notify-job-id"
   operation attribute.

   The Printer MUST accept the request in any of the target job's 'not-
   completed' states, i.e., 'pending', 'pending-held', 'processing', or
   'processing-stopped'. The Printer MUST NOT change the job's "job-
   state" attribute because of this operation.  If the target job is in
   any of the 'completed' states, i.e., 'completed', 'canceled', or
   'aborted, then the Printer MUST reject the request and return the
   'client-error-not-possible' status code; the response MUST NOT
   contain any Subscription Attribute Groups.

   Access Rights:  To create Per-Job Subscription Objects, the
   authenticated user (see [RFC2911] section 8.3) performing this
   operation MUST either be the job owner or have Operator or
   Administrator access rights for this Printer (see [RFC2911] sections
   1 and 8.5).  Otherwise the Printer MUST reject the operation and
   return: the 'client-error-forbidden', 'client-error-not-
   authenticated', or 'client-error-not-authorized' status code as
   appropriate.


11.1.1.1 Create-Job-Subscriptions Request

   The following groups of attributes are part of the Create-Job-
   Subscriptions Request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.1.

      Target:
         The "printer-uri" attribute which defines the target for this
         operation as described in [RFC2911] section 3.1.5.

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      Requesting User Name:
         The "requesting-user-name" attribute SHOULD be supplied by the
         client as described in [RFC2911] section 8.3.

      notify-job-id (integer(1:MAX)):
         The client MUST supply this attribute and it MUST specify the
         Job object to associate the Per-Job Subscription with. The
         value of "notify-job-id" MUST be the value of the "job-id" of
         the associated Job object. If the client does not supply this
         attribute, the Printer MUST reject this request with a 'client-
         error-bad-request' status code.

   Group 2-N: Subscription Template Attributes

       For each occurrence of this group:

          The client MUST supply one or more Subscription Template
          Attributes in any order. See section 5.3 for a description of
          each such attribute. See section 5.2 for details on processing
          these attributes.


11.1.1.2 Create-Job-Subscriptions Response

   The Printer MUST return to the client the following sets of
   attributes as part of a Create-Job-Subscriptions response:

   Group 1: Operation Attributes

      Status Message:
         In addition to the REQUIRED status code returned in every
         response, the response OPTIONALLY includes a "status-message"
         (text(255)) and/or a "detailed-status-message" (text(MAX))
         operation attribute as described in [RFC2911] sections 13 and
         3.1.6.

         In this group, the Printer can return any status codes defined
         in [RFC2911] and section 16. The following is a description of
         the important status codes:

            successful-ok: the Printer created all Subscription Objects
               requested (see [RFC2911]).
            successful-ok-ignored-subscriptions: the Printer created
               some Subscription Objects requested but some failed. The
               Subscription Attributes Groups with a "notify-status-
               code" attribute are the ones that failed (see section
               16.1).

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            client-error-ignored-all-subscriptions: the Printer created
               no Subscription Objects requested and all failed. The
               Subscription Attributes Groups with a "notify-status-
               code" attribute are the ones that failed (see section
               16.2).
            client-error-not-possible: For this operation and other
               Per-Job Subscription operations, this error can occur
               because the specified Job has already completed (see
               [RFC2911], whether or not the Job is retained in the Job
               Retention and/or Job History phases (see [RFC2911]
               section 4.3.7.1).

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 for details on returning
         Unsupported Attributes. This group does not contain any
         unsupported Subscription Template Attributes; they are returned
         in the Subscription Attributes Group (see below).

   Group 3-N: Subscription Attributes

         These groups MUST be returned unless the Printer is unable to
         interpret the entire request, e.g., the "status-code" parameter
         returned in Group 1 has the value: 'client-error-bad-request'.

         "notify-status-code" (type2 enum):
            Indicates the status of this subscription (see section 17
            for the status code definitions).  Section 5.2 defines when
            this attribute MUST be present in this group.

         See section 5.2 for details on the contents of each occurrence
         of this group.


11.1.2 Create-Printer-Subscriptions operation

   The operation is identical to Create-Job-Subscriptions with
   exceptions noted in this section.

   The operation creates Per-Printer Subscription Objects instead of
   Per-Job Subscription Objects, and associates each newly created Per-
   Printer Subscription Object with the Printer specified by the
   operation target rather than with a specific Job.


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   The Printer MUST accept the request in any of its states, i.e.,
   'idle', 'processing', or 'stopped'. The Printer MUST NOT change its
   "printer-state" attribute because of this operation.

   Access Rights:  To create Per-Printer Subscription Objects, the
   authenticated user (see [RFC2911] section 8.3) performing this
   operation MUST have Operator or Administrator access rights for this
   Printer (see [RFC2911] sections 1 and 8.5).  Otherwise, the Printer
   MUST reject the operation and return: the 'client-error-forbidden',
   'client-error-not-authenticated', or 'client-error-not-authorized'
   status code as appropriate.


11.1.2.1 Create-Printer-Subscriptions Request

   The groups are identical to the Create-Job-Subscriptions (see section
   11.1.1.1) except that the Operation Attributes group MUST NOT contain
   the  "notify-job-id" attribute.  If the client does supply the
   "notify-job-id" attribute, then the Printer MUST treat it as any
   other unsupported Operation attribute and MUST return it in the
   Unsupported Attributes group.


11.1.2.2 Create-Printer-Subscriptions Response

   The groups are identical to the Create-Job-Subscriptions (see section
   11.1.1.2).


11.1.3 Job Creation Operations - Extensions for Notification

   This document extends the Job Creation operations (see section 3.2)
   to create Subscription Objects as a part of the operation.

   The Job Creation operations are identical to Create-Job-Subscriptions
   operation with exceptions noted in this section.

   Unlike the Create-Job-Subscriptions operation, a Job Creation
   operation associates the newly created Subscription Objects with the
   Job object created by this operation. The operation succeeds if and
   only if the Job creation succeeds. If the Printer does not create
   some or all of the requested Subscription Objects, the Printer MUST
   return a  'successful-ok-ignored-subscriptions' status-code instead
   of a 'successful-ok' status-code, but the Printer MUST NOT reject the
   operation because of a failure to create Subscription Objects.




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   If the Job Creation operation includes a Job Template group, the
   client MUST supply it after the Operation Attributes group and before
   the first Subscription Template Attributes Group.

   If a Printer does not support this Notification specification, then
   it MUST treat the Subscription Attributes Group like an unknown group
   and ignore it (see [RFC2911] section 5.2.2).  Because the Printer
   ignores the Subscription Attributes Group, it doesn't return them in
   the response either, thus indicating to the client that the Printer
   doesn't support Notification.

   After completion of a successful Job Creation operation, the Printer
   generates a 'job-created' event (see section 5.3.2.1.3).

   Access Rights:  To create Per-Job Subscription Objects, the
   authenticated user (see [RFC2911] section 8.3) performing this
   operation MUST either have permission to create Jobs on the Printer
   or have Operator or Administrator access rights for this Printer (see
   [RFC2911] sections 1 and 8.5).  Otherwise the Printer MUST reject the
   operation and return: the 'client-error-forbidden', 'client-error-
   not-authenticated', or 'client-error-not-authorized' status code as
   appropriate.


11.1.3.1 Job Creation Request

   The groups for this operation are sufficiently different from the
   Create-Job-Subscriptions operation that they are all presented here.
   The following groups of attributes are supplied as part of a Job
   Creation Request:

   Group 1: Operation Attributes

         Same as defined in [RFC2911] for Print-Job, Print-URI, and
         Create-Job requests.

   Group 2: Job Template Attributes

         The client OPTIONALLY supplies a set of Job Template attributes
         as defined in [RFC2911] section 4.2.

   Group 3 to N: Subscription Template Attributes

         The same as Group 2-N in Create-Job-Subscriptions. See section
         11.1.1.1.
   Group N+1: Document Content  (Print-Job only)

         The client MUST supply the document data to be processed.

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11.1.3.2 Job Creation Response

   The Printer MUST return to the client the following sets of
   attributes as part of a Print-Job, Print-URI, and Create-Job
   Response:

   Group 1: Operation Attributes

      Status Message:

         As defined in [RFC2911] for Print-Job, Print-URI, and Create-
         Job requests.

         In this group, the Printer can return any status codes defined
         in [RFC2911] and section 16. The following is a description of
         the important status codes:

            successful-ok: the Printer created the Job and all
               Subscription Objects requested (see [RFC2911].
            successful-ok-ignored-subscriptions: the Printer created
               the Job and not all of the Subscription Objects requested
               (see section 16.1). This status-code hides 'successful-
               ok-xxx' status-codes that could reveal problems in Job
               creation. The Printer MUST NOT return the 'client-error-
               ignored-all-subscriptions' status code for Job Creation
               operations because the Printer returns an error status-
               code only when it fails to create a Job.

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 for details on returning
         Unsupported Attributes. This group does not contain any
         unsupported Subscription Template Attributes; they are returned
         in the Subscription Attributes Group (see below).

   Group 3: Job Object Attributes

         The "job-id" of the Job Object just created, etc., as defined
         in [RFC2911] for Print-Job, Print-URI, and Create-Job requests.

   Group 4 to N: Subscription Attributes


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         These groups MUST be returned if and only if the client
         supplied Subscription Template Attributes and the operation was
         accepted.
         See section 5.2 for details on the contents of each occurrence
         of this group.


11.2 Other Operations

   This section defines other operations on Subscription objects.


11.2.1 Restart-Job Operation - Extensions for Notification

   The Restart-Job operation [RFC2911] is neither a Job Creation
   operation nor a Subscription Creation operation (see section 3.2).
   For the Restart-Job operation, the client MUST NOT supply any Job
   Subscription Attributes Groups.  The Printer MUST treat any supplied
   Job Subscription Attributes as unsupported attributes.

   For this operation, the Printer does not return a job-id or any
   Subscription Attributes groups because the Printer reuses the
   existing Job object with the same job-id and the existing Per-Job
   Subscription Objects with the same subscription-ids.  However, after
   successful completion of this operation, the Printer generates a
   'job-created' event (see section 5.3.2.1.3).


11.2.2 Validate-Job Operation - Extensions for Notification

   A client can test whether one or more Subscription Objects could be
   created using the Validate-Job operation.  The client supplies one or
   more Subscription Template Attributes Groups (defined in section
   5.3), just as in a Job Creation request.

   A Printer MUST support this extension to this operation.

   The Printer MUST accept requests that are identical to the Job
   Creation request defined in section 11.1.3.1, except that the request
   MUST NOT contain document data.

   The Printer MUST return the same groups and attributes as the Print-
   Job operation (section 11.1.3.1) with the following exceptions.  The
   Printer MUST NOT return a Job Object Attributes Group because no Job
   is created. The Printer MUST NOT return the "notify-subscription-id"
   attribute in any Subscription Attribute Group because no Subscription
   Object is created.


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   If the Printer would succeed in creating a Subscription Object, the
   corresponding Subscription Attributes Group either has no 'status-
   code' attribute or a 'status-code' attribute with a value of
   'successful-ok-too-many-events' or 'successful-ok-ignored-or-
   substituted-attributes' (see sections 5.2 and 17). The status-codes
   have the same meaning as in Job Creation except the results state
   what "would happen".

   The Printer MUST validate Subscription Template Attributes Groups in
   the same manner as the Job Creation operations.


11.2.3 Get-Printer-Attributes - Extensions for Notification

   This operation is extended so that it returns Printer attributes
   defined in this document.

   A Printer MUST support this extension to this operation.

   In addition to the requirements of [RFC2911] section 3.2.5, a Printer
   MUST support the following additional values for the "requested-
   attributes" Operation attribute in this operation and return such
   attributes in the Printer Object Attributes group of its response.

     1.Subscription Template Attributes: Each supported attribute in
       column 2 of Table 1.

     2.New Printer Description Attributes: Each supported attribute in
       section 6.

     3.New Group Name: The 'subscription-template' group name, which
       names all supported Subscription Template Attribute in column 2
       of Table 1. This group name is also used in the Get-
       Subscription-Attributes and Get-Subscriptions operation with an
       analogous meaning.

     4.Extended Group Name: The 'all' group name, which names all
       Printer attributes according to [RFC2911] section 3.2.5.  In
       this extension 'all' names all attributes specified in [RFC2911]
       plus those named in items 1 and 2 of this list.


11.2.4 Get-Subscription-Attributes operation

   This operation allows a client to request the values of the
   attributes of a Subscription Object.

   A Printer MUST support this operation.

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   This operation is almost identical to the Get-Job-Attributes
   operation (see [RFC2911] section 3.3.4).  The only differences are
   that the operation is directed at a Subscription Object rather than a
   Job object, and the returned attribute group contains Subscription
   Object attributes rather than Job object attributes.


11.2.4.1 Get-Subscription-Attributes Request

   The following groups of attributes are part of the Get-Subscription-
   Attributes request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in section [RFC2911] 3.1.4.1.

      Target:
         The "printer-uri" attribute which defines the target for this
         operation as described in [RFC2911] section 3.1.5.

      "notify-subscription-id" (integer (1:MAX)):
         The client MUST supply this attribute.  The Printer MUST
         support this attribute. This attribute specifies the
         Subscription Object from which the client is requesting
         attributes. If the client omits this attribute, the Printer
         MUST reject this request with the 'client-error-bad-request'
         status code.

      Requesting User Name:
         The "requesting-user-name" attribute SHOULD be supplied by the
         client as described in [RFC2911] section 8.3.

       "requested-attributes" (1setOf keyword):
         The client OPTIONALLY supplies this attribute.  The Printer
         MUST support this attribute. This attribute specifies the
         attributes of the specified Subscription Object that the
         Printer MUST return in the response.  Each value of this
         attribute is either an attribute name (defined in sections 5.3
         and 5.4) or an attribute group name. The attribute group names
         are:

            - 'subscription-template': all attributes that are both
               defined in section 5.3 and present on the specified
               Subscription Object (column 1 of Table 1).



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            - 'subscription-description': all attributes that are both
               defined in section 5.4 and present on the specified
               Subscription Object (Table 2).
            - 'all': all attributes that are present on the specified
               Subscription Object.

     A Printer MUST support all these group names.

         If the client omits this attribute, the Printer MUST respond as
         if this attribute had been supplied with a value of 'all'.


11.2.4.2 Get-Subscription-Attributes Response

   The Printer returns the following sets of attributes as part of the
   Get-Subscription-Attributes Response:

   Group 1: Operation Attributes

      Status Message:
         Same as [RFC2911].

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.  The
         "attributes-natural-language" MAY be the natural language of
         the Subscription Object, rather than the one requested.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 and section 3.2.5.2 for details on
         returning Unsupported Attributes.

         The response NEED NOT contain the "requested-attributes"
         operation attribute with any supplied keyword values that were
         requested by the client but are not supported by the IPP
         object. If the Printer object does return unsupported
         attributes referenced in the "requested-attributes" operation
         attribute, the values of the "requested-attributes" attribute
         returned MUST include only the unsupported keywords that were
         requested by the client.  If the client had requested a group
         name, such as 'all', the resulting unsupported attributes
         returned MUST NOT include attribute keyword names described in
         the standard but not supported by the implementation.

   Group 3: Subscription Attributes



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         This group contains a set of attributes with their current
         values. Each attribute in this group:

          a)MUST be specified by the "requested-attributes" attribute
            in the request, AND

          b)MUST be present on the specified Subscription Object AND

          c)MUST  NOT be restricted by the security policy in force.
            For example, a Printer MAY prohibit a client who is not the
            creator of a Subscription Object from seeing some or all of
            its attributes. See [RFC2911] section 8.

         The Printer can return the attributes of the Subscription
         Object in any order. The client MUST accept the attributes in
         any order.


11.2.5 Get-Subscriptions operation

   This operation allows a client to retrieve the values of attributes
   of all Subscription Objects belonging to a Job or Printer.

   A Printer MUST supported this operation.

   This operation is similar to the Get-Subscription-Attributes
   operation, except that this Get-Subscriptions operation returns
   attributes from possibly more than one object.

   This operation is similar to the Get-Jobs operation (see [RFC2911]
   section 3.2.6), except that the operation returns Subscription
   Objects rather than Job objects.


11.2.5.1 Get-Subscriptions Request

   The following groups of attributes are part of the Get-Subscriptions
   request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.1.

      Target:
         The "printer-uri" attribute which defines the target for this
         operation as described in [RFC2911] section 3.1.5.

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      Requesting User Name:
         The "requesting-user-name" attribute SHOULD be supplied by the
         client as described in [RFC2911] section 8.3.

      "notify-job-id" (integer(1:MAX)):
         If the client specifies this attribute, the Printer returns the
         specified attributes of all Per-Job Subscription Objects
         associated with the Job whose "job-id" attribute value equals
         the value of this attribute. If the client does not specify
         this attribute, the Printer returns the specified attributes of
         all Per-Printer Subscription Objects. Note: there is no way to
         get all Per-Job Subscriptions known to the Printer in a single
         operation.  A Get-Jobs operation followed by a Get-
         Subscriptions operation for each Job will return all Per-Job
         Subscriptions.

      "limit" (integer(1:MAX)):
         The client OPTIONALLY supplies this attribute.  The Printer
         MUST support this attribute.  It is an integer value that
         determines the maximum number of Subscription Objects that a
         client will receive from the Printer even if the "my-
         subscriptions" attribute constrains which Subscription Objects
         are returned.  The limit is a "stateless limit" in that if the
         value supplied by the client is 'N', then only the first 'N'
         Subscription Objects are returned in the Get-Subscriptions
         Response.  There is no mechanism to allow for the next 'M'
         Subscription Objects after the first 'N' Subscription Objects.
         If the client does not supply this attribute, the Printer
         responds with all applicable Subscription Objects.

      "requested-attributes" (1setOf type2 keyword):
         The client OPTIONALLY supplies this attribute.  The Printer
         MUST support this attribute. This attribute specifies the
         attributes of the specified Subscription Objects that the
         Printer MUST return in the response.  Each value of this
         attribute is either an attribute name (defined in sections 5.3
         and 5.4) or an attribute group name (defined in section
         11.2.4.1). If the client omits this attribute, the Printer MUST
         respond as if the client had supplied this attribute with the
         one value: 'notify-subscription-id'.

      "my-subscriptions" (boolean):
         The client OPTIONALLY supplies this attribute.  The Printer
         MUST support this attribute.  If the value is 'false', the
         Printer MUST consider the Subscription Objects from all users
         as candidates. If the value is 'true', the Printer MUST return
         the Subscription Objects created by the requesting user of this

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         request.  If the client does not supply this attribute, the
         Printer MUST respond as if the client had supplied the
         attribute with a value of 'false'.  The means for
         authenticating the requesting user and matching the
         Subscription Objects is similar to that for Jobs which is
         described in [RFC2911] section 8.


11.2.5.2 Get-Subscriptions Response

   The Printer returns the following sets of attributes as part of the
   Get-Subscriptions Response:

   Group 1: Operation Attributes

      Status Message:
         Same as [RFC2911].

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.

   Group 2: Unsupported Attributes

         Same as for Get-Subscription-Attributes.

   Groups 3 to N: Subscription Attributes

         The Printer responds with one Subscription Attributes Group for
         each requested Subscription Object (see the "notify-job-id"
         attribute in the Operation Attributes Group of this operation).

         The Printer returns Subscription Objects in any order.

         If the "limit" attribute is present in the Operation Attributes
         group of the request, the number of Subscription Attributes
         Groups in the response MUST NOT exceed the value of the "limit"
         attribute.

         It there are no Subscription Objects associated with the
         specified Job or Printer, the Printer MUST return zero
         Subscription Attributes Groups and it MUST NOT treat this case
         as an error, i.e., the status-code MUST be 'successful-ok'
         unless something else causes the status code to have some other
         value.




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         See the Group 3 response (Subscription Attributes Group) of the
         Get-Subscription-Attributes operation (section 11.2.4.2) for
         the attributes that a Printer returns in this group.


11.2.6 Renew-Subscription operation

   This operation allows a client to request the Printer to extend the
   lease on a Per-Printer Subscription Object.

   The Printer MUST support this operation.

   The Printer MUST accept this request for a Per-Printer Subscription
   Object in any of the target Printer's states, i.e., 'idle',
   'processing', or 'stopped', but MUST NOT change the Printer's
   "printer-state" attribute.

   The Printer MUST reject this request for a Per-Job Subscription
   Object because it has no lease (see section 5.4.3). The status code
   returned MUST be 'client-error-not-possible'.

   Access Rights: The authenticated user (see [RFC2911] section 8.3)
   performing this operation MUST either be the owner of the Per-Printer
   Subscription Object or have Operator or Administrator access rights
   for the Printer (see [RFC2911] sections 1 and 8.5).  Otherwise, the
   Printer MUST reject the operation and return: the 'client-error-
   forbidden', 'client-error-not-authenticated', or 'client-error-not-
   authorized' status code as appropriate.


11.2.6.1 Renew-Subscription Request

   The following groups of attributes are part of the Renew-Subscription
   Request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.1.

      Target:
         The "printer-uri" attribute which defines the target for this
         operation as described in [RFC2911] section 3.1.5.

      "notify-subscription-id" (integer (1:MAX)):
         The client MUST supply this attribute.  The Printer MUST
         support this attribute. This attribute specifies the Per-

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         Printer Subscription Object whose lease the Printer MUST renew.
         If the client omits this attribute, the Printer MUST reject
         this request with the 'client-error-bad-request' status code.

      Requesting User Name:
         The "requesting-user-name" (name(MAX)) attribute SHOULD be
         supplied by the client as described in [RFC2911] section 8.3.

   Group 2: Subscription Template Attributes


       "notify-lease-duration" (integer(0:MAX)):
         The client MAY supply this attribute. It indicates the number
         of seconds to renew the lease for the specified Subscription
         Object.  A value of 0 requests an infinite lease (which MAY
         require Operator access rights). If the client omits this
         attribute, the Printer MUST use the value of the Printer's
         "notify-lease-duration-default" attribute. See section 5.3.7
         for more details.


11.2.6.2 Renew-Subscription Response

   The Printer returns the following sets of attributes as part of the
   Renew-Subscription Response:

   Group 1: Operation Attributes

      Status Message:
         Same as [RFC2911].

         The following are some of the status codes returned (see
         [RFC2911]:

            successful-ok: The operation successfully renewed the lease
               on the Subscription Object for the requested duration.
            successful-ok-ignored-or-substituted-attributes: The
               operation successfully renewed the lease on the
               Subscription Object for some duration other than the
               amount requested.
            client-error-not-possible: The operation failed because the
               "notify-subscription-id" Operation attribute identified a
               Per-Job Subscription Object.
            client-error-not-found: The operation failed because the
               "notify-subscription-id" Operation attribute identified a
               non-existent Subscription Object.



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      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.  The
         "attributes-natural-language" MAY be the natural language of
         the Subscription Object, rather than the one requested.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 for details on returning
         Unsupported Attributes.

   Group 3: Subscription Attributes

   The Printer MUST return the following Subscription Attribute:

      "notify-lease-duration" (integer(0:MAX)):
         The value of this attribute MUST be the number of seconds that
         the Printer has granted for the lease of the Subscription
         Object (see section 5.3.7 for details, such as the value of
         this attribute when the Printer doesn't support the requested
         value).




11.2.7 Cancel-Subscription operation

   This operation allows a client to delete a Subscription Object and
   stop the Printer from sending more Event Notifications.  Once
   performed, there is no way to reference the Subscription Object.

   A Printer MUST supported this operation.

   The Printer MUST accept this request in any of the target Printer's
   states, i.e., 'idle', 'processing', or 'stopped', but MUST NOT change
   the Printer's "printer-state" attribute.

   If the specified Subscription Object is a Per-Job Subscription
   Object, the Printer MUST accept this request in any of the target
   Job's states, but MUST NOT change the Job's "job-state" attribute or
   affect the Job.

   Access Rights: The authenticated user (see [RFC2911] section 8.3)
   performing this operation MUST either be the owner of the
   Subscription Object or have Operator or Administrator access rights
   for the Printer (see [RFC2911] sections 1 and 8.5).  Otherwise, the
   Printer MUST reject the operation and return: the 'client-error-


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   forbidden', 'client-error-not-authenticated', or 'client-error-not-
   authorized' status code as appropriate.

   Note:  There is no way to change any attributes on a Subscription
   Object, except the "notify-lease-duration" attribute (using the
   Renew-Subscription operation).  In order to change other attributes,
   a client performs a Subscription Creation Operation and Cancel-
   Subscription operation on the old Subscription Object. If the client
   wants to avoid missing Event Notifications, it performs the
   Subscription Creation Operation first. If this order would create too
   many Subscription Objects on the Printer, the client reverses the
   order.


11.2.7.1 Cancel-Subscription Request

   The following groups of attributes are part of the Cancel-
   Subscription Request:

   Group 1: Operation Attributes

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.1.

      Target:
         The "printer-uri" attribute which defines the target for this
         operation as described in [RFC2911] section 3.1.5.

      "notify-subscription-id" (integer (1:MAX)):
         The client MUST supply this attribute.  The Printer MUST
         support this attribute. This attribute specifies the
         Subscription Object that the Printer MUST cancel. If the client
         omits this attribute, the Printer MUST reject this request with
         the 'client-error-bad-request' status code.

      Requesting User Name:
         The "requesting-user-name" attribute SHOULD be supplied by the
         client as described in [RFC2911] section 8.3.


11.2.7.2 Cancel-Subscription Response

   The Printer returns the following sets of attributes as part of the
   Cancel-Subscription Response:

   Group 1: Operation Attributes


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      Status Message:
         Same as [RFC2911].

         The following are some of the status codes returned (see
         [RFC2911]:

            successful-ok: The operation successfully canceled
               (deleted) the Subscription Object.
            client-error-not-found: The operation failed because the
               "notify-subscription-id" Operation attribute identified a
               non-existent Subscription Object.

      Natural Language and Character Set:
         The "attributes-charset" and "attributes-natural-language"
         attributes as described in [RFC2911] section 3.1.4.2.  The
         "attributes-natural-language" MAY be the natural language of
         the Subscription Object, rather than the one requested.

   Group 2: Unsupported Attributes

         See [RFC2911] section 3.1.7 for details on returning
         Unsupported Attributes.


12 Conformance Requirements

   It is OPTIONAL for IPP clients and Printers to implement this Event
   Notification specification.

   If this Event Notification specification is implemented, Printers
   MUST:

      -  meet the Conformance Requirements detailed in section 5 of
         [RFC2911].

      -  support the Subscription Template Attributes Group in requests
         and the Subscription Attributes Group in responses.

      -  support all of the following attributes:

         a.REQUIRED Subscription Object attributes in section 5.
         b.REQUIRED Printer Description object attributes in section 6.
         c.REQUIRED attributes in Event Notification content in section
           8.

      -  send Event Notifications that conform to the requirements of
         section 9 and the requirements of the Delivery Method Document
         for each supported Delivery Method (the conformance

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         requirements for Delivery Method Documents is specified in
         section 10).

      -  for all of the Job Creation Operations that the Printer
         supports, MUST support the REQUIRED extensions for notification
         defined in section 11.1.3.

      -  meet the conformance requirements for operations as described
         in Table 16 and meet the requirements for Printers as specified
         in the indicated sub-sections of section 11:


        Table 16 - Printer Conformance Requirements for Operations


   Operation                                         Printer
                                                     Conformance
                                                     Requirements


   Create-Printer-Subscriptions (section 11.1.2)     REQUIRED

   Create-Job-Subscriptions (section 11.1.1)         OPTIONAL

   Get-Subscription-Attributes (section 11.2.3)      REQUIRED

   Get-Subscriptions (section 11.2.5)                REQUIRED

   Renew-Subscription (section 11.2.6)               REQUIRED

   Cancel-Subscription (section 11.2.7)              REQUIRED



13 IANA Considerations

   This section contains the registration information for IANA to add to
   the various IPP Registries according to the procedures defined in RFC
   2911 [RFC2911] section 6 to cover the definitions in this document.
   In addition, this section defines how Events and Delivery Methods
   will be registered when they are defined in other documents.

     Note to RFC Editors:  Replace RFC NNNN below with the RFC number
     for this document, so that it accurately reflects the content of
     the information for the IANA Registry.




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13.1 Attribute Registrations

   The following table lists all the attributes defined in this
   document.   These are to be registered according to the procedures in
   RFC 2911 [RFC2911] section 6.2.

   Subscription Template attributes:               Ref.      Section:
   notify-recipient-uri (uri)                      RFC NNNN     5.3.1
   notify-schemes-supported  (1setOf uriScheme)    RFC NNNN     5.3.1
   notify-events (1setOf type2 keyword)            RFC NNNN     5.3.2
   notify-events-default (1setOf type2 keyword)    RFC NNNN     5.3.2
   notify-events-supported (1setOf type2 keyword)  RFC NNNN     5.3.2
   notify-max-events-supported (integer(2:MAX))    RFC NNNN     5.3.2
   notify-attributes (1setOf type2 keyword)        RFC NNNN     5.3.3
   notify-attributes-supported (1setOf type2 keyword)
                                                   RFC NNNN     5.3.3
   notify-user-data (octetString(63))              RFC NNNN     5.3.4
   notify-charset (charset)                        RFC NNNN     5.3.5
   notify-natural-language (naturalLanguage)       RFC NNNN     5.3.6
   notify-lease-duration (integer(0:67108863))     RFC NNNN     5.3.7
   notify-lease-duration-default (integer(0:67108863))
                                                   RFC NNNN     5.3.7
   notify-lease-duration-supported (1setOf (integer(0: 67108863) |
   rangeOfInteger(0:67108863)))                    RFC NNNN     5.3.7
   notify-time-interval (integer(0:MAX))           RFC NNNN     5.3.8

   Subscription Description Attributes:
   notify-subscription-id  (integer (1:MAX)))      RFC NNNN     5.4.1
   notify-sequence-number (integer (0:MAX)))       RFC NNNN     5.4.2
   notify-lease-expiration-time (integer(0:MAX)))  RFC NNNN     5.4.3
   notify-printer-up-time (integer(1:MAX)))        RFC NNNN     5.4.4
   notify-printer-uri (uri))                       RFC NNNN     5.4.5
   notify-job-id (integer(1:MAX)))                 RFC NNNN     5.4.6
   notify-subscriber-user-name (name(MAX)))        RFC NNNN     5.4.7

   Printer Description Attributes:
   printer-state-change-time (integer(1:MAX)))     RFC NNNN     6.1
   printer-state-change-date-time (dateTime))      RFC NNNN     6.2

   Attributes Only in Event Notifications
   notify-subscribed-event (type2 keyword)         RFC NNNN     8.1
   notify-text (text(MAX))                         RFC NNNN     8.2

   The resulting attribute registrations will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attributes/
   area.



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13.2 Additional Enum Attribute Value Registrations for the "operations-
    supported" Printer Attribute

   The following table lists all the new enum attribute values defined
   in this document as additional type2 enum values for use with the
   "operations-supported" Printer Description attribute.  These are to
   be registered according to the procedures in RFC 2911 [RFC2911]
   section 6.1.

   type2 enum Attribute Values:        Value       Ref.      Section:
   Create-Printer-Subscriptions        0x0016      RFC NNNN     7.1
   Create-Job-Subscriptions            0x0017      RFC NNNN     7.1
   Get-Subscription-Attributes         0x0018      RFC NNNN     7.1
   Get-Subscriptions                   0x0019      RFC NNNN     7.1
   Renew-Subscription                  0x001A      RFC NNNN     7.1
   Cancel-Subscription                 0x001B      RFC NNNN     7.1

   The resulting enum attribute value registrations will be published in
   the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
   values/operations-supported/
   area.


13.3 Operation Registrations

   The following table lists all of the operations defined in this
   document.  These are to be registered according to the procedures in
   RFC 2911 [RFC2911] section 6.4.

   Operations:                                    Ref.      Section:
   Create-Job-Subscriptions Operation             RFC NNNN    11.1.1
   Create-Printer-Subscriptions Operation         RFC NNNN    11.1.2
   Job Creation Operations - Extensions           RFC NNNN    11.1.3
   Validate-Job Operation - Extensions            RFC NNNN    0
   Get-Printer-Attributes - Extensions            RFC NNNN    11.2.3
   Get-Subscription-Attributes Operation          RFC NNNN    11.2.4
   Get-Subscriptions Operation                    RFC NNNN    11.2.5
   Renew-Subscription Operation                   RFC NNNN    11.2.6
   Cancel-Subscription Operation                  RFC NNNN    11.2.7

   The resulting operation registrations will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/operations/
   area.





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13.4 Status code Registrations

   The following table lists all the status codes defined in this
   document.  These are to be registered according to the procedures in
   RFC 2911 [RFC2911] section 6.6.

   Status codes:                                     Ref.      Section:
   successful-ok-ignored-subscriptions (0x0003)      RFC NNNN      16.1
   client-error-ignored-all-subscriptions (0x0414)   RFC NNNN      16.2

   Status Codes in Subscription Attributes Groups:
   client-error-uri-scheme-not-supported (0x040C)    RFC NNNN      17.1
   client-error-too-many-subscriptions (0x0415)      RFC NNNN      17.2
   successful-ok-too-many-events (0x0005)            RFC NNNN      17.3
   successful-ok-ignored-or-substituted-attributes (0x0001)
                                                     RFC NNNN      17.4

   The resulting status code registrations will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/status-codes/
   area.


13.5 Attribute Group tag Registrations

   The following table lists all the attribute group tags defined in
   this document.  These are to be registered according to the
   procedures in RFC 2911 [RFC2911] section 6.5.

   Attribute Group Tags:                Tag Value:   Ref.      Section:
   subscription-attributes-tag          0x06         RFC NNNN       18
   event-notification-attributes-tag    0x07         RFC NNNN       18

   The resulting attribute group tag registrations will be published in
   the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-group-
   tags/
   area.


13.6 Registration of Events

   When other document define additional type2 keywords to be used with
   the "notify-events" Subscription Template attribute (see section
   5.3.2)), these event keywords will be registered according to the
   procedures of [RFC2911] section 7.1 as additional attribute values
   for use with the "notify-events" Subscription Template attribute,
   i.e., the "notify-events", "notify-events-default", and "notify-
   events-supported" attributes.

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   Therefore, the IPP Registry entry for an Event will be of the form:

   type2 enum Attribute Values:                   Ref.       Section:
   <scheme name>                                  RFC xxxx   m.n

   The resulting type2 keyword attribute values will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
      values/notify-events/
   area.


13.7  Registration of Event Notification Delivery Methods

   This section describes the requirements and procedures for
   registration and publication of Event Notification Delivery Methods
   and for the submission of such proposals.


13.7.1 Requirements for Registration of Event Notification Delivery
     Methods

   Registered IPP Event Notification Delivery Methods are expected to
   follow a number of requirements described below.


13.7.1.1 Required Characteristics

   A Delivery Method Document MUST either (1) contain all of the
   semantics of the Delivery Method or (2) contain the IPP Delivery
   Method registration requirements and a profile of some other protocol
   that in combination is the Delivery Method (e.g., mailto).  In either
   case, the Delivery Method Document (and any documents it requires)
   MUST define a URL and be a standards track, informational, or
   experimental RFC that the meets the requirements of [RFC2717].

   IPP Event Notification Delivery Method Documents MUST meet the
   requirements of this document (see sections 9 and 10).

   In addition, a Delivery Method Document MUST contain the following
   information:

     Type of registration:  IPP Event Notification Delivery Method
     Name of this delivery method:
     Proposed URL scheme name of this delivery method:
     Name of proposer:
     Address of proposer:
     Email address of proposer:


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     Is this delivery method REQUIRED or OPTIONAL for conformance to the
     IPP Event Notification and Subscriptions document:
     Is this delivery method defining Machine Consumable and/or Human
     Consumable content:



13.7.1.2 Naming Requirements

   Exactly one name MUST be assigned to each Delivery Method.

   Each assigned name MUST uniquely identify a single Delivery Method.
   All Delivery Method names MUST conform to the rules for URL scheme
   names, according to [RFC2396] and [RFC2717] for schemes in the IETF
   tree.


13.7.1.3 Functionality Requirements

   Delivery Methods MUST function as a protocol that is capable of
   delivering (push or pull) IPP Event Notifications to Notification
   Recipients.


13.7.1.4 Usage and Implementation Requirements

   Use of a large number of Delivery Methods may hamper
   interoperability.  However, the use of a large number of undocumented
   and/or unlabelled Delivery Methods hampers interoperability even
   more.

   A Delivery Method should therefore be registered ONLY if it adds
   significant functionality that is valuable to a large community, OR
   if it documents existing practice in a large community.  Note that
   Delivery Methods registered for the second reason should be
   explicitly marked as being of limited or specialized use and should
   only be used with prior bilateral agreement.


13.7.1.5 Publication Requirements

   Delivery Method Documents MUST be published in a standards track,
   informational, or experimental RFCs.






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13.7.2 Registration Procedure

   The IPP WG is developing a small number of Delivery Methods which are
   intended to be published as standards track RFCs.  However, some
   parties may wish to register additional Delivery Methods in the
   future.  This section describes the procedures for these additional
   Delivery Methods.


13.7.2.1 Present the proposal to the Community

   First the Delivery Method Document MUST be an Internet-Draft with a
   target category of standards track, informational, or experimental.
   The same MUST be true for any documents that it references.

   Send the proposed Delivery Method Document proposal to the
   "ipp@pwg.org" mailing list.  This mailing list has been established
   by [RFC2911] for reviewing proposed registrations and discussing
   other IPP matters.  Proposed Delivery Method Documents are not
   formally registered and MUST NOT be used until approved.

   The intent of the public posting is to solicit comments and feedback
   on the definition and suitability of the Delivery Method and the name
   chosen for it over a four week period.


13.7.2.2 Delivery Method Reviewer

   The Delivery Method Reviewer is the same person who has been
   appointed by the IETF Application Area Director(s) as the IPP
   Designated Expert according to [RFC2911] and [IANA-CON].  When the
   four week period is over and the IPP Designated Expert is convinced
   that consensus has been achieved, the IPP Designated Expert either
   approves the request for registration or rejects it.  Rejection may
   occur because of significant objections raised on the list or
   objections raised externally.

   Decisions made by the Reviewer must be posted to the ipp@pwg.org
   mailing list within 14 days. Decisions made by the Reviewer may be
   appealed to the IESG.


13.7.2.3 IANA Registration

   Provided that the Delivery Method registration proposal has either
   passed review or has been successfully appealed to the IESG, the IANA
   will register the Delivery Method and make it available to the
   community.

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13.7.3 Delivery Method Document Registrations

   Each Delivery Method Document defines a URI scheme which is
   registered as an additional value of the "notify-schemes-supported"
   Printer attribute.  These uriScheme values will be registered
   according to the procedures of [RFC2911] section 7.1 for additional
   attribute values.  Therefore, the IPP Registry entry for a Delivery
   Method will be of the form:

   uriScheme Attribute Values:                    Ref.       Section:
   <scheme name>                                  RFC xxxx   m.n

   The resulting Delivery Method URI schemes will be published in the
   ftp://ftp.iana.org/in-notes/iana/assignments/ipp/attribute-
   values/notify-schemes-supported/
   area.


13.7.4 Registration Template

   To: ipp@pwg.org
   Subject: Registration of a new Delivery Method

   Delivery Method name:

   (All names must be suitable for use as the value of a URL scheme in
   the IETF tree)

   Published specification(s):

   (A specification for the Delivery Method must be openly available
   that accurately describes what is being registered.)

   Person & email address to contact for further information:

14 Internationalization Considerations

   This IPP Notification specification continues support for the
   internationalization of [RFC2911] of attributes containing text
   strings and names.  Allowing a Subscribing Client to specify a
   different natural language and charset for each Subscription Object
   increases the internationalization support.

   The Printer MUST be able to localize the content of Human Consumable
   Event Notifications and to localize the value of "notify-text"
   attribute in Machine Consumable Event Notifications that it sends to
   Notification Recipients. For localization, the Printer MUST use the
   value of the "notify-charset" attribute and the "notify-natural-

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   language" attribute in the Subscription Object supplied by the
   Subscribing Client.


15 Security Considerations

   By far the biggest security concern is the abuse of notification:
   sending unwanted Event Notifications to third parties (i.e., spam).
   The problem is made worse by notification addresses that may be
   redistributed to multiple parties (e.g., mailing lists).  There exist
   scenarios where third party notification is required (see Scenario #2
   and #3 in [ipp-not-req]).  The fully secure solution would require
   active agreement of all recipients before sending out anything.
   However, requirement #9 in [ipp-req] ("There is no requirement for
   IPP Printer receiving the print request to validate the identity of
   an Event recipient") argues against this.  Certain systems may decide
   to disallow third party Event Notifications (a traditional fax
   model).

   Clients submitting Notification requests to the IPP Printer have the
   same security issues as submitting an IPP/1.1 print job request.  The
   same mechanisms used by IPP/1.1 can therefore be used by the client
   Notification submission.  Operations that require authentication can
   use the HTTP authentication.  Operations that require privacy can use
   the HTTP/TLS privacy.  As with IPP/1.1 Print Jobs, if there is no
   security on Subscription Objects, sequential assignment of
   subscription-ids exposes the system to a passive traffic monitoring
   threat.

   The Notification access control model should be similar to the IPP
   access control model for Jobs.  Creating a Per-Printer Subscription
   Object is associated with a user.  Only the creator or an Operator
   can cancel the Subscription Object.  The system may limit the listing
   of items to only those items owned by the user.  Some Subscription
   Objects (e.g., those that have a lifetime longer than a job) can be
   done only by privileged users (users having Operator and/or
   Administrator access rights), if that is the authorization policy.

   The standard security concerns (delivery to the right user, privacy
   of content, tamper proof content) apply to the Delivery Method.  IPP
   should use the security mechanism of the Delivery Method used.  Some
   delivery mechanisms are more secure than others.  Therefore,
   sensitive Event Notifications should use the Delivery Method that has
   the strongest security.





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16 Status Codes

   The following status codes are defined as extensions for Notification
   and are returned as the value of the "status-code" parameter in the
   Operation Attributes Group of a response (see [RFC2911] section
   3.1.6.1). Operations in this document can also return the status
   codes defined in section 13 of [RFC2911]. The 'successful-ok' status
   code is an example of such a status code.


16.1 successful-ok-ignored-subscriptions (0x0003)

   The Subscription Creation Operation was unable to create all
   requested Subscription Objects.

   For a Create-Job-Subscriptions or Create-Printer-Subscriptions
   operation, this status code means that the Printer created one or
   more Subscription Objects, but not all requested Subscription
   Objects.

   For a Job Creation operation, this status code means that the Printer
   created the Job along with zero or more Subscription Objects. The
   Printer returns this status code even if other job attributes are
   unsupported or in conflict.  That is, if an IPP Printer finds a
   warning that would allow it to return  'successful-ok-ignored-
   subscriptions' and either 'successful-ok-ignored-or-substituted-
   attributes' and/or 'successful-ok-conflicting-attributes', it MUST
   return 'successful-ok-ignored-subscriptions'.


16.2 client-error-ignored-all-subscriptions (0x0414)

   This status code is the same as 'successful-ok-ignored-subscriptions'
   except that only the Create-Job-Subscriptions and Create-Printer-
   Subscriptions operation return it. They return this status code only
   when the Printer creates zero Subscription Objects.


17 Status Codes in Subscription Attributes Groups

   This section contains values of the "notify-status-code" (type2 enum)
   attribute that the Printer returns in a Subscription Attributes Group
   in a response when the corresponding Subscription Object:

     1.is not created or

     2.is created and some of the client-supplied attributes are not
       supported.

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   The following sections are ordered in decreasing order of importance
   of the status-codes.


17.1 client-error-uri-scheme-not-supported (0x040C)

   This status code is defined in [RFC2911]. This document extends its
   meaning and allows it to be in a Subscription Attributes Group of a
   response.

   The scheme of the client-supplied URI in a "notify-recipient-uri"
   Subscription Template Attribute in a Subscription Creation Operation
   is not supported.  See section 5.3.1.


17.2 client-error-too-many-subscriptions (0x0415)

   The number of Subscription Objects supported by the Printer would be
   exceeded if this Subscription Object were created (see section 5.2).


17.3 successful-ok-too-many-events (0x0005)

   The client supplied more Events in the "notify-events" operation
   attribute of a Subscription Creation Operation than the Printer
   supports, as indicated in its "notify-max-events-supported" Printer
   attribute (see section 5.3.2).


17.4 successful-ok-ignored-or-substituted-attributes (0x0001)

   This status code is defined in [RFC2911]. This document extends its
   meaning to include unsupported Subscription Template Attributes and
   it can appear in a Subscription Attributes Group.


18 Encodings of Additional Attribute Tags

   This section assigns values to two attributes tags as extensions to
   the encoding defined in [RFC2910]).

   The "subscription-attributes-tag" delimits Subscription Template
   Attributes Groups in requests and Subscription Attributes Groups in
   responses.

   The "event-notification-attributes-tag" delimits Event Notifications
   in Delivery Methods that use an IPP-like encoding.


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   The following table specifies the values for the delimiter tags:


       Tag Value (Hex)   Meaning


       0x06              "subscription-attributes-tag"

       0x07              "event-notification-attributes-tag"


19 References

   [IANA-CON]
     Narte, T. and Alvestrand, H.T.:  Guidelines for Writing an IANA
     Considerations Section in RFCs, BCP 26, RFC 2434, October 1998.

   [ipp-not-req]
     deBry, R., Lewis, H., Hastings, T., "Internet Printing
     Protocol/1.1: Requirements for IPP Notifications", <draft-ietf-ipp-
     not-06.txt>, work in progress, July 17, 2001.

   [ipp-prog]
     Hastings, T., Bergman, R., Lewis, H., "IPP: Job Progress
          Attributes", <draft-ietf-ipp-job-prog-03.txt> work in
          progress,  July 17, 2001.

   [ipp-set]
     Kugler, C., Hastings, T., Herriot, R., Lewis, H, "Internet Printing
     Protocol (IPP): Job and Printer Set Operations", <draft-ietf-ipp-
     job-printer-set-ops-04.txt>, work in progress, July 17, 2001.

   [RFC2026]
     S. Bradner, "The Internet Standards Process -- Revision 3", RFC
     2026, October 1996.

   [RFC2119]
     S. Bradner, "Key words for use in RFCs to Indicate Requirement
     Levels", RFC 2119 , March 1997

   [RFC2396]
     Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource
     Identifiers (URI): Generic Syntax", RFC 2396, August 1998.

   [RFC2565]
     Herriot, R., Butler, S., Moore, P., and R. Turner, "Internet
     Printing Protocol/1.0: Encoding and Transport", RFC 2565, April
     1999.

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   [RFC2566]
     deBry, R., , Hastings, T., Herriot, R., Isaacson, S., Powell, P.,
     "Internet Printing Protocol/1.0: Model and Semantics", RFC 2566,
     April 1999.

   [RFC2567]
     Wright, D., "Design Goals for an Internet Printing Protocol", RFC
     2567, April 1999.

   [RFC2568]
     Zilles, S., "Rationale for the Structure and Model and Protocol for
     the Internet Printing Protocol", RFC 2568, April 1999.

   [RFC2569]
     Herriot, R., Hastings, T., Jacobs, N., Martin, J., "Mapping between
     LPD and IPP Protocols", RFC 2569, April 1999.

   [RFC2717]
     R. Petke and I. King, "Registration Procedures for URL Scheme
     Names", RFC 2717, November 1999.

   [RFC2910]
     Herriot, R., Butler, S., Moore, P., Turner, R., "Internet Printing
     Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.

   [RFC2911]
     deBry, R., , Hastings, T., Herriot, R., Isaacson, S., Powell, P.,
     "Internet Printing Protocol/1.1: Model and Semantics", RFC 2911,
     September 2000.


20 Author's Addresses

   Robert Herriot
   Xerox Corporation
   3400 Hillview Ave., Bldg #1
   Palo Alto, CA 94304

   Phone: 650-813-7696
   Fax:  650-813-6860
   Email: robert.herriot@pahv.xerox.com

   Tom Hastings
   Xerox Corporation
   737 Hawaii St.  ESAE 231
   El Segundo, CA  90245

   Phone: 310-333-6413

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   Fax: 310-333-5514
   e-mail: hastings@cp10.es.xerox.com


   Scott A. Isaacson
   Novell, Inc.
   122 E 1700 S
   Provo, UT  84606

   Phone: 801-861-7366
   Fax: 801-861-2517
   e-mail: sisaacson@novell.com


   Roger deBry
   Utah Valley State College
   Orem, UT 84058

   Phone: (801) 222-8000
   EMail: debryro@uvsc.edu

   Jay Martin
   Underscore Inc.
   9 Jacqueline St.
   Hudson, NH 03051-5308
   603-889-7000
   fax: 775-414-0245
   e-mail: jkm@underscore.com


   Michael Shepherd
   Xerox Corporation
   800 Phillips Road  MS 128-51E
   Webster, NY  14450

   Phone: 716-422-2338
   Fax: 716-265-8871
   e-mail: mshepherd@crt.xerox.com











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   Ron Bergman
   Hitachi Koki Imaging Solutions
   1757 Tapo Canyon Road
   Simi Valley, CA 93063-3394

   Phone: 805-578-4421
   Fax:  805-578-4001
   Email: rbergma@hitachi-hkis.com

   IPP Web Page:  http://www.pwg.org/ipp/
   IPP Mailing List:  ipp@pwg.org

   To subscribe to the ipp mailing list, send the following email:
     1) send it to majordomo@pwg.org
     2) leave the subject line blank
     3) put the following two lines in the message body:
          subscribe ipp
          end

   Implementers of this specification document are encouraged to join
   the IPP Mailing List in order to participate in any discussions of
   clarification issues and review of registration proposals for
   additional attributes and values.  In order to reduce spam the
   mailing list rejects mail from non-subscribers, so you must subscribe
   to the mailing list in order to send a question or comment to the
   mailing list.


A.   Appendix - Model for Notification with Cascading Printers

   With this model (see Figure 2), there is an intervening Print server
   between the human user and the output-device. So the system
   effectively has two Printers.  There are two cases to consider.

   1.When the Printer 1 (in the server) generates Events, the system
     behaves like the client and Printer in Figure 1. In this case,
     Printer 1 sends Event Notifications that are shown as Event
     Notifications (A) of  Figure 2,.

   2.When the Printer 2 (in the output-device) generates Events, there
     are two possible system configurations:

     a)Printer 1 forwards the client-supplied Subscription Creation
       Operations to the downstream Printer 2 and lets Printer 2 send
       the Event Notifications directly to the Notification Recipients
       supplied by the Client (Event Notifications(C) in the diagram).



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     b)Printer 1 performs the client-supplied Subscription Creation
       Operations and also forwards the Subscription Creation
       Operations to Printer 2 with the Notification Recipient changed
       to be the Printer 1. When an Event occurs in Printer 2, Printer
       2 sends the Event Notification (B) to Notification Recipient of
       Printer 1, which relays the received Event Notification (B) to
       the client-supplied Notification Recipient (as Event
       Notifications(A) in the diagram). Note, when a client performs a
       Subscription Creation Operation, Printer 1 need not forward the
       Subscription Creation Operation to Printer 2 if it would create
       a duplicate Subscription Object on Printer 2.

   Note: when Printer 1 is forwarding Subscription Creation Operations
   to Printer 2, it may request Printer 2 to create additional
   Subscription Objects (called "piggy-backing").  Piggy-backing is
   useful when:

      -  Device A is configured to accept (IPP or non-IPP) requests from
         other servers.

      -  Server S wants to receive Job Events that the client didn't
         request and Server S wants these Events for jobs it submits and
         not for other jobs.

                              server S                       device A
                           +------------+                 +------------+
                           |            |                 |            |
   +--------+ Subscription | ###########|                 | ###########|
   | client |--Creation ----># Printer #|  Subscription   | # Printer #|
   +--------+  Operation   | # Object 1#|---Creation------|># Object 2#|
                           | ###|#######|   Operation     | ####|#|####|
                           +----|---^---+                 +-----|-|----+
   +--------+     Event         |   |                           | |
   |Notific-|<-Notifications(A)-+   +-- Event Notifications(B)--+ |
   |ation Re|<-------------Event Notifications(C)-----------------+
   |cipient |
   +--------+

         Figure 2 - Model for Notification with Cascading Printers


B.   Appendix - Distributed Model for Notification

   A Printer implementation could use some other remote notification
   service to provide some or most of the service. For example, the
   remote notification service could send Event Notifications using
   Delivery Methods that are not directly supported by the output device
   or server. Or, the remote notification service could store

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   Subscription Objects (passed to it from the output device in response
   to Subscription Creation requests), accept Events, format the Event
   Notification in the natural language of the Notification Recipient,
   and send the Event Notifications to the Notification Recipient(s).

   Figure 3 shows this partitioning. The interface between the output
   device (or server) and the remote notification service is outside the
   scope of this document and is intended to be transparent to the
   client and this document.  The combination of the output device (or
   server) and the notification service together constitute an IPP
   Printer conforming to this Notification document.



                                         ***********************
                                         *
                                            * Printer (including
                                         * the distributed
                                         * Notification Service)
                                         *
                                            * output device or server
                                            * +---------------+
      PDA, desktop, or server               * +  ###########  +
           +--------+                       * |  # partial #  |
           | client |---IPP Subscription--------># Printer #  |
           +--------+   Creation operation  * |  # Object  #  |
                                            * |  #####|#####  |
                                            * +-------|-------+
                                            *         | Subscriptions
                                            *         | OR Event
        +------------+                      *         | Notifications
        |Notification|   IPP-defined        *  +------v--------+
        |Recipient   |<--Event Notifications---| Notification  |
        +------------+                      *  | Service       |
                                            *  +---------------+
                                            *
                                            *************************
     *** = Implementation configuration opaque boundary


    Figure 3 - Opaque Use of a Notification Service Transparent to the
                                  Client


C.   Appendix - Extended Notification Recipient

   The model allows for an extended Notification Recipient that is
   itself a notification service that forwards each Event Notification

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   to another recipient (called the Ultimate Notification Recipient in
   this section). The Delivery Method to the Ultimate Recipient is
   probably different from the Delivery Method used by the Printer to
   the extended Notification Recipient.

   This extended Notification Recipient is transparent to the Printer
   but not to the client.

   When a client performs a Subscription Creation Operation, it
   specifies the extended Notification Recipient as it would any
   Notification Recipient. In addition, the client specifies the
   Ultimate Notification Recipient in the Subscription Creation
   Operation in a manner specified by the extended Notification
   Recipient. Typically, it is either some bytes in the value of
   "notify-user-data" or some additional parameter in the value of
   "notify-recipient-uri". The client also subscribes directly with the
   extended Notification Recipient (by means outside this document),
   since it is a notification service in its own right.

   The IPP Printer treats the extended Notification Recipient like any
   other Notification Recipient and the IPP Printer is not aware of the
   forwarding. The Delivery Method that the extended Notification
   Recipient uses for delivering the Event Notification to the Ultimate
   Notification Recipient is beyond the scope of this document and is
   transparent to the IPP Printer.

   Examples of this extended Notification Recipient are paging,
   immediate messaging services, general notification services, and NOS
   vendors' infrastructure.  Figure 4 shows this approach.


      PDA, desktop, or server                    server or output device
                                                      +---------------+
          +--------+                                  |  ###########  |
          | client |---Subscription Creation -----------># Printer #  |
          +--------+       Operation                  |  # Object  #  |
                                                      |  #####|#####  |
   +------------+     +------------+   IPP-defined    +-------|-------+
   |Ultimate    | any |Notification|<--Event Notifications----+
   |Notification|<----|Recipient   |
   |Recipient   |     +------------+
   +------------+     (Notification Service)

    Figure 4 - Use of an Extended Notification Recipient transparent to
                                the Printer




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D.   Appendix - Details about Conformance Terminology

   The following paragraphs provide more details about conformance
      terminology.

   REQUIRED - an adjective used to indicate that a conforming IPP
      Printer implementation MUST support the indicated operation,
      object, attribute, attribute value, status code, or out-of-band
      value in requests and responses.  See [RFC2911] "Appendix A -
      Terminology for a definition of "support".  Since support of this
      entire Notification specification is OPTIONAL for conformance to
      IPP/1.0 or IPP/1.1, the use of the term REQUIRED in this document
      means "REQUIRED if this OPTIONAL Notification specification is
      implemented".

   RECOMMENDED - an adjective used to indicate that a conforming IPP
      Printer implementation is recommended to support the indicated
      operation, object, attribute, attribute value, status code, or
      out-of-band value in requests and responses.  Since support of
      this entire Notification specification is OPTIONAL for conformance
      to IPP/1.0 or IPP/1.1, the use of the term RECOMMENDED in this
      document means "RECOMMENDED if this OPTIONAL Notification
      specification is implemented".

   OPTIONAL - an adjective used to indicate that a conforming IPP
      Printer implementation MAY, but is NOT REQUIRED to, support the
      indicated operation, object, attribute, attribute value, status
      code, or out-of-band value in requests and responses.


E.   Appendix - Object Model for Notification

   This section describes the Notification object model that adds a
   Subscription Object which together with the Job and Printer object
   provide the complete Notification semantics.














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   The object relationships can be seen pictorially as:


     Subscription Objects (Per-Printer Subscriptions)     Printer object
     +----+                                               +------------+
     | s1 |<--------------------------------------------->|            |
     +----++                                              |            |
      | s2 |<-------------------------------------------->|     p1     |
      +----++                                             |            |
       | s3 |<------------------------------------------->|            |
       +----+                                             +------------+
                      Job objects
                      +---------+
                      |         |
       +----+         |   j1    |
       | s4 |<------->|         |
       +----+         |         |
                      |         |    s4 is a Per-Job Subscription Object
                      ++--------++
                       |         |
         +----+        |   j2    |
         | s5 |<------>|         |
         +----++       |         |
          | s6 |<----->|         |    s5 and s6 are Per-Job Subscription
          +----+       ++--------++                  Objects
                        |         |
                        |   j3    |
                        |         |
                        |         |         <----> indicates association
                        +---------+

                 Figure 5 - Object Model for Notification

     s1, s2, and s3 are Per-Printer Subscription Objects and can
     identify Printer and/or Job Events.
     s4, s5, and s6 are Per-Job Subscription Objects and can identify
     Printer and/or Job Events.

E.1  Appendix - Object relationships

   This sub-section defines the object relationships between the
   Printer, Job, and Subscription Objects by example.  Whether Per-
   Printer Subscription Objects are actually contained in a Printer
   object or are just bi-directionally associated with them in some way
   is IMPLEMENTATION DEPENDENT and is transparent to the client.
   Similarly, whether Per-Job Subscription Objects are actually
   contained in a Job object or are just bi-directionally associated


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   with them in some way is IMPLEMENTATION DEPENDENT and is transparent
   to the client.  The object relationships are defined as follows:


E.2  Printer Object and Per-Printer Subscription Objects

     1.The Printer object contains (is associated with) zero or more
       Per-Printer Subscription Objects (p1 contains s1-s3 Per-Printer
       Subscription Objects).

     2.Each Per-Printer Subscription Object (s1, s2, and s3) is
       contained in (or is associated with) exactly one Printer object
       (p1).


E.3  Job Object and Per-Job Subscription Objects

     1.A Job object (j1, j2, j3) is associated with zero or more Per-
       Job Subscription Objects (s4-s6).  Job j1 is associated with
       Per-Job Subscription Object s4, Job j2 is associated with Per-
       Job Subscription Objects s5 and s6, and Job j3 is not associated
       with any Per-Job Subscription Object.

     2.Each Per-Job Subscription Object is associated with exactly one
       Job object.


F.   Appendix - Per-Job versus Per-Printer Subscription Objects

   Per-Job and Per-Printer Subscription Objects are quite similar.
   Either type of Subscription Object can subscribe to Job Events,
   Printer Events, or both.  Both types of Subscription Objects can be
   queried using the Get-Subscriptions and Get-Subscription-Attributes
   operations and canceled using the Cancel-Subscription operation.
   Both types of Subscription Objects create Subscription Objects which
   have the same Subscription Object attributes defined.  However, there
   are some semantic differences between Per-Job Subscription Objects
   and Per-Printer Subscription Objects.  A Per-Job Subscription Object
   is established by the client when submitting a job and after creating
   the job using the Create-Job-Subscriptions operation by specifying
   the "job-id" of the Job with the "notify-job-id" attribute.  A Per-
   Printer Subscription Object is established between a client and a
   Printer using the Create-Printer-Subscriptions operation.  Some
   specific differences are:

     1.A client usually creates one or more Per-Job Subscription
       Objects as part of the Job Creation operations (Create-Job,
       Print-Job, and Print-URI), rather than using the OPTIONAL

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       Create-Job-Subscriptions operation, especially since Printer
       implementations NEED NOT support the Create-Job-Subscriptions
       operation, since it is OPTIONAL.

     2.For Per-Job Subscription Objects, the Subscription Object is
       only valid while the job is "not-complete" (see sections 5.4.3)
       while for the Per-Printer Subscription Objects, the Subscription
       Object is valid until the time (in seconds) that the Printer
       returned in the "notify-lease-expiration-time" operation
       attribute.

     3.Job Events in a Per-Job Subscription Object apply only to "one
       job" (the Job created by the Job Creation  operation or
       references by the Create-Job-Subscriptions operation) while Job
       Events in a Per-Printer Subscription Object apply to ALL jobs
       contained in the IPP Printer.


G.   Appendix - Description of the base IPP documents

   The base set of IPP documents includes:

     Design Goals for an Internet Printing Protocol [RFC2567]
     Rationale for the Structure and Model and Protocol for the Internet
        Printing Protocol [RFC2568]
     Internet Printing Protocol/1.1: Model and Semantics [RFC2911]
     Internet Printing Protocol/1.1: Encoding and Transport [RFC2910]
     Internet Printing Protocol/1.1: Implementer's Guide [IPP-IIG]
     Mapping between LPD and IPP Protocols [RFC2569]

   The "Design Goals for an Internet Printing Protocol" document takes a
   broad look at distributed printing functionality, and it enumerates
   real-life scenarios that help to clarify the features that need to be
   included in a printing protocol for the Internet.  It identifies
   requirements for three types of users: end users, operators, and
   administrators.  It calls out a subset of end user requirements that
   are satisfied in IPP/1.0 [RFC2566, RFC2565].  A few OPTIONAL operator
   operations have been added to IPP/1.1 [RFC2911, RFC2910].

   The "Rationale for the Structure and Model and Protocol for the
   Internet Printing Protocol" document describes IPP from a high level
   view, defines a roadmap for the various documents that form the suite
   of IPP specification documents, and gives background and rationale
   for the IETF IPP working group's major decisions.

   The "Internet Printing Protocol/1.1: Model and Semantics" document
   describes a simplified model with abstract objects, their attributes,
   and their operations.  The model introduces a Printer and a Job.  The

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   Job supports multiple documents per Job.  The model document also
   addresses how security, internationalization, and directory issues
   are addressed.

   The "Internet Printing Protocol/1.1: Encoding and Transport" document
   is a formal mapping of the abstract operations and attributes defined
   in the model document onto HTTP/1.1 [RFC2616].  It also defines the
   encoding rules for a new Internet MIME media type called
   "application/ipp".  This document also defines the rules for
   transporting over HTTP a message body whose Content-Type is
   "application/ipp".  This document defines the 'ipp' scheme for
   identifying IPP printers and jobs.

   The "Internet Printing Protocol/1.1: Implementer's Guide" document
   gives insight and advice to implementers of IPP clients and IPP
   objects.  It is intended to help them understand IPP/1.1 and some of
   the considerations that may assist them in the design of their client
   and/or IPP object implementations.  For example, a typical order of
   processing requests is given, including error checking.  Motivation
   for some of the specification decisions is also included.

   The "Mapping between LPD and IPP Protocols" document gives some
   advice to implementers of gateways between IPP and LPD (Line Printer
   Daemon) implementations.


H.   Appendix - Full Copyright Statement

   Copyright (C) The Internet Society (1998,1999,2000,2001). All Rights
   Reserved

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.


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   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.






































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