<pre>Network Working Group                                           R. deBry
Request for Comments: 3382                     Utah Valley State College
Updates: <a href="./rfc2910">2910</a>, <a href="./rfc2911">2911</a>                                           R. Herriot
Category: Standards Track                                     Consultant
                                                             T. Hastings
                                                                 K. Ocke
                                                               P. Zehler
                                                       Xerox Corporation
                                                          September 2002


                   <span class="h1">Internet Printing Protocol (IPP):</span>
                   <span class="h1">The 'collection' attribute syntax</span>

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document specifies an OPTIONAL attribute syntax called
   'collection' for use with the Internet Printing Protocol (IPP/1.0 and
   IPP/1.1).  A 'collection' is a container holding one or more named
   values, which are called "member" attributes.  A collection allows
   data to be grouped like a PostScript dictionary or a Java Map.  This
   document also specifies the conformance requirements for a definition
   document that defines a collection attribute.  Finally, this document
   gives some illustrative example collection attribute definitions that
   are not intended as actual attribute specifications.

Table of Contents

   <a href="#section-1">1</a> Introduction.....................................................<a href="#page-3">3</a>
   <a href="#section-1.1">1.1</a> Problem Statement..............................................<a href="#page-3">3</a>
   <a href="#section-1.2">1.2</a> Solution.......................................................<a href="#page-3">3</a>
   <a href="#section-2">2</a> Terminology......................................................<a href="#page-4">4</a>
   <a href="#section-2.1">2.1</a> Conformance Terminology........................................<a href="#page-4">4</a>
   <a href="#section-2.2">2.2</a> Other terminology..............................................<a href="#page-5">5</a>
   <a href="#section-3">3</a> Definition of a Collection Attribute.............................<a href="#page-5">5</a>
   <a href="#section-3.1">3.1</a> Information to Include.........................................<a href="#page-5">5</a>



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   <a href="#section-3.2">3.2</a> Nested Collections.............................................<a href="#page-9">9</a>
   <a href="#section-4">4</a> Collection Attributes as Attributes in Operations................<a href="#page-9">9</a>
   <a href="#section-4.1">4.1</a> General Rules..................................................<a href="#page-9">9</a>
   <a href="#section-4.2">4.2</a> Unsupported Values.............................................<a href="#page-9">9</a>
   <a href="#section-5">5</a> Example definition of a collection attribute.....................<a href="#page-9">9</a>
   <a href="#section-5.1">5.1</a> media-col (collection)........................................<a href="#page-10">10</a>
   <a href="#section-5.1.1">5.1.1</a> media-color (type3 keyword | name(MAX)......................<a href="#page-10">10</a>
   <a href="#section-5.1.2">5.1.2</a> media-size (collection).....................................<a href="#page-11">11</a>
   <a href="#section-5.2">5.2</a> media-col-default (collection)................................<a href="#page-11">11</a>
   <a href="#section-5.3">5.3</a> media-col-ready (1setOf collection)...........................<a href="#page-12">12</a>
   <a href="#section-5.4">5.4</a> media-col-supported (1setOf type2 keyword)....................<a href="#page-12">12</a>
   <a href="#section-6">6</a> A Second Example Definition Of A Collection Attribute...........<a href="#page-12">12</a>
   <a href="#section-7">7</a> Encoding........................................................<a href="#page-13">13</a>
   7.1 Additional tags defined for representing a collection
       attribute value...............................................<a href="#page-13">13</a>
   <a href="#section-7.2">7.2</a> Example encoding: "media-col" (collection)....................<a href="#page-14">14</a>
   <a href="#section-8">8</a> Legacy issues...................................................<a href="#page-20">20</a>
   <a href="#section-9">9</a> IANA Considerations.............................................<a href="#page-20">20</a>
   <a href="#section-10">10</a> Internationalization Considerations............................<a href="#page-20">20</a>
   <a href="#section-11">11</a> Security Considerations........................................<a href="#page-21">21</a>
   <a href="#section-12">12</a> References.....................................................<a href="#page-21">21</a>
   <a href="#appendix-A">Appendix A</a>: Encoding Example of a Simple Collection (Informative).22
   <a href="#appendix-B">Appendix B</a>: Encoding Example of 1setOf Collection (Informative)...<a href="#page-25">25</a>
   <a href="#appendix-C">Appendix C</a>: Encoding Example of Collection containing 1setOf XXX
               attribute (Informative)...............................<a href="#page-31">31</a>
   <a href="#appendix-D">Appendix D</a>: Description of the Base IPP Documents (Informative)...<a href="#page-35">35</a>
   Authors' Addresses................................................<a href="#page-36">36</a>
   Full Copyright Statement..........................................<a href="#page-38">38</a>

Table of Tables

   Table 1 - "media-col" member attributes...........................<a href="#page-10">10</a>
   Table 2 - "media-size" collection member attributes...............<a href="#page-11">11</a>
   Table 3 - Tags defined for encoding the 'collection' attribute
             syntax .................................................<a href="#page-13">13</a>
   Table 4 - Overview Encoding of "media-col" collection.............<a href="#page-15">15</a>
   Table 5 - Example Encoding of "media-col" collection..............<a href="#page-16">16</a>
   Table 6 - Overview Encoding of simple collection..................<a href="#page-22">22</a>
   Table 7 - Example Encoding of simple collection...................<a href="#page-22">22</a>
   Table 8 - Overview Encoding of 1setOf collection..................<a href="#page-25">25</a>
   Table 9 - Example Encoding of 1setOf collection...................<a href="#page-26">26</a>
   Table 10 - Overview Encoding of collection with 1setOf value......<a href="#page-31">31</a>
   Table 11 - Example Encoding of collection with 1setOf value.......<a href="#page-32">32</a>








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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a> Introduction</span>

   This document is an OPTIONAL extension to IPP/1.0 [RFC2565, <a href="./rfc2566">RFC2566</a>]
   and IPP/1.1 [RFC2911, <a href="./rfc2910">RFC2910</a>].  For a description of the base IPP
   documents see <a href="#appendix-D">Appendix D</a>.

<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a> Problem Statement</span>

   The IPP Model and Semantics [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>] supports most of the common
   data structures that are available in programming languages.  It
   lacks a mechanism for grouping several attributes of different types.
   The Java language uses the Map to solve this problem and PostScript
   has a dictionary.  The new mechanism for grouping attributes together
   (called 'collection' mechanism) must allow for optional members and
   the subsequent addition of new members.

   The 'collection' mechanism must be encoded in a manner consistent
   with existing 1.0 and 1.1 parsing rules (see [<a href="./rfc2910" title="&quot;Internet Printing Protocol/1.1: Encoding and Transport&quot;">RFC2910</a>]).  Current 1.0
   and 1.1 parsers that don't support the 'collection' mechanism must
   not confuse collections or parts of a collection they receive with
   other attributes.

<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a> Solution</span>

   The new mechanism is a new IPP attribute syntax called a
   'collection'.  As such, each collection value is a value of an
   attribute whose attribute syntax type is defined to be a
   'collection'.  Such an attribute is called a collection attribute.
   The name of the collection attribute serves to identify the
   collection value in an operation request or response, as with any
   attribute value.

   The 'collection' attribute syntax is a container holding one or more
   named values (i.e., attributes), which are called member attributes.
   Each collection attribute definition document lists the mandatory and
   optional member attributes of each collection value.  A collection
   value is similar to an IPP attribute group in a request or a
   response, such as the operation attributes group.  They both consist
   of a set of attributes.

   As with any attribute syntax, the document that defines a collection
   attribute specifies whether the attribute is single-valued
   (collection) or multi-valued (1setOf collection).  If the attribute
   is multi-valued (1setOf collection), each collection value MUST be a
   separate instance of a single definition of a collection, i.e., it
   MUST have the same member attributes except for OPTIONAL member
   attributes.  If we view each collection definition as a separate
   syntax type, this rule continues the IPP/1.1 notion that each



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   attribute has a single type or pattern (e.g., "keyword | name" is a
   pattern).  Without this rule, the supported values would be more
   difficult to describe and the mechanism defined in item 4 of <a href="#section-3.1">section</a>
   <a href="#section-3.1">3.1</a> would not be sufficient.

   The name of each member attribute MUST be unique for a collection
   attribute, but MAY be the same as the name of a member attribute in
   another collection attribute and/or MAY be the same as the name of an
   attribute that is not a member of a collection.  The rules for naming
   member attributes are given in <a href="#section-3.1">section 3.1</a>.

   Each member attribute can have any attribute syntax type, including
   'collection', and can be either single-valued or multi-valued.  The
   length of a collection value is not limited.  However, the length of
   each member attribute MUST NOT exceed the limit of its attribute
   syntax.

   The member attributes in a collection MAY be in any order in a
   request or response.  When a client sends a collection attribute to
   the Printer, the order that the Printer stores the member attributes
   of the collection value and the order returned in a response MAY be
   different from the order sent by the client.

   A collection value MUST NOT contain two or more member attributes
   with the same attribute name.  Such a collection is mal-formed.
   Clients MUST NOT submit such malformed requests and Printers MUST NOT
   return such malformed responses.  If such a malformed request is
   submitted to a Printer, the Printer MUST (depending on
   implementation) either (1) reject the request with the 'client-
   error-bad-request' status code (see <a href="./rfc2911#section-13.1.4.1">[RFC2911] section&nbsp;13.1.4.1</a>), or
   (2) accept the request and use only one of each duplicate member
   attributes.

<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a> Terminology</span>

   This section defines terminology used throughout this document.

<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a> Conformance Terminology</span>

   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 <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a> [<a href="./rfc2119">RFC2119</a>] and <a href="./rfc2911#section-12.1">[RFC2911],
   section&nbsp;12.1</a>.  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.





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<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a> Other terminology</span>

   This document uses terms such as Job object (or Job), IPP Printer
   object (or Printer), "operation", "request", response", "attributes",
   "keywords", and "support".  These terms have special meaning and are
   defined in the model terminology <a href="./rfc2911#section-12.2">[RFC2911] section&nbsp;12.2</a>.  The
   following additional terms are introduced in this document:

      collection: an attribute syntax in which each attribute value is a
         set of attributes, called member attributes.

      member attribute: an attribute that is defined to be used as one
         of the attributes in a collection.

      collection attribute: an attribute whose definition specifies the
         'collection' attribute syntax and each of the member attributes
         that MAY occur in a collection attribute value.

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a> Definition of a Collection Attribute</span>

   This section describes the requirements for any collection attribute
   definition.

<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a> Information to Include</span>

   When a specification document defines an "xxx" collection attribute,
   i.e., an attribute whose attribute syntax type is 'collection' or
   '1setOf collection'; the definition document MUST include the
   following aspects of the attribute semantics.  Suppose the "xxx"
   collection attribute contains N member attributes named  "aaa1",
   "aaa2", ..., "aaaN" ("aaaI" represents any one of these N member
   attributes).

   1. The name of the collection attribute MUST be specified  (e.g.,
      "xxx").  The selection of the name "xxx" MUST follow the same
      rules for uniqueness as for attributes of any other syntax type,
      (as defined by IPP/1.1) unless "xxx" is a member attribute of
      another collection.  Then the selection of the name "xxx" MUST
      follow the rules for uniqueness defined in item 5a) of this list.

   2. The collection attribute syntax MUST be of type 'collection' or
      '1setOf collection'.

   3. The context of the collection attribute MUST be specified, i.e.,
      whether the attribute is an operation attribute, a Job Template
      attribute, a Job Description attribute, a Printer Description
      attribute, a member attribute of a particular collection
      attribute, etc.



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   4. An "xxx-supported" attribute MUST be specified and it has one of
      the following two forms:

      a) "xxx-supported" is a "1setOf collection", which enumerates all
         of the supported collection values of "xxx".  If a collection
         of this form contains a nested collection, it MUST be of the
         same form.

         For example, "media-size-supported" might have the values {{x-
         dimension:210, y-dimension:297},{x-dimension:297, y-
         dimension:420}} to show that it supports two values of "media
         size": A4 (210x297) and A3 (297x420).  It does not support
         other combinations of "x-dimension" and "y-dimension" member
         attributes, such as 210x420 or 297x297, and it does not support
         non-enumerated values, such as 420x595.

      b) "xxx-supported" is a "1setOf type2 keyword", which enumerates
         the names of all of the member attributes of "xxx": "aaa1",
         "aaa2", ..., "aaaN".  If a collection of this form contains a
         nested collection, it MAY be of either form.  See item 5f)
         below for details on supported values of member attributes.

         For example, "media-col-supported" might have the keyword
         values: "media-size" and "media-color".

   5. The member attributes MUST be defined.  For each member attribute,
      the definition document MUST provide the following information:

      a) The member attribute's name (e.g., "aaa") MUST be unique within
         the collection being defined and MUST either:

           i) reuse the attribute name of another attribute (that is
              unique across the entire IPP attribute name space) and
              have the same syntax and semantics as the reused attribute
              (if the condition of item 4b) above is met).  For example,
              a member attribute definition could reuse the IPP/1.1
              "media" attribute.

          ii) potentially occur elsewhere in the entire IPP attribute
              name space.  (if the condition of item 4a) above is met).
              For example, a member attribute could be "x-dimension",
              which could potentially occur in another collection or as
              an attribute outside of a collection.

         iii) be unique across the entire IPP attribute name space (if
              the condition of item 4b) above is met).  For example, a
              member attribute could be "media-color" which must be
              unique across the entire IPP attribute name space.



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      b) Whether the member attribute is REQUIRED or OPTIONAL for the
         Printer to support.

      c) Whether the member attribute is REQUIRED or OPTIONAL for the
         client to supply in a request.

      d) The member attribute's syntax type, which can be any attribute
         syntax, including '1setOf X', 'collection', and '1setOf
         collection'.  If this attribute name reuses the name of another
         attribute (case of item a1 above), it MUST have the same
         attribute syntax, including cardinality (whether or not
         1setOf).

      e) The semantics of the "aaa" member attribute.  The semantic
         definition MUST include a description of any constraint or
         boundary conditions the member attribute places on the
         associated attribute, especially if the attribute reuses the
         name of another attribute (case of item a1 above).

      f) The supported values for each "aaaI" member attribute (of the
         member attributes  "aaa1", "aaa2", ..., "aaaN") is specified by
         one of two mechanisms.

           i) If "xxx-supported" is a "1setOf collection" (see item 4a)
              above), the value for each "aaaI" is specified in each
              collection value of "xxx-supported", in the context of
              other member attributes.  That is, "xxx-supported"
              enumerates all supported values of "xxx".

          ii) If the value of "xxx-supported" is a "1setOf type2
              keyword" (see item 4b) above), the supported values of
              "aaaI" are the values specified by either i) the "aaaI-
              supported" attribute or ii) the definition of the member
              attribute "aaaI" within the document defining the "xxx"
              attribute.  The values of each member attribute "aaaI" are
              specified independently of other member attributes, though
              a Printer is not required to support all combinations of
              supported values.

              For example, "media-col-supported" might have the keyword
              values: "media-size" and "media-color".  Using the first
              method for defining supported values (an "aaaI-supported"
              attribute), the collection values of "media-col" are
              combinations of values of "media-size-supported" and
              "media-color-supported".  If "media-size-supported" has
              the values of '210x297' and '297x420' and "media-color-
              supported" has the values of 'white' and 'pink', the




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              Printer might support only the combinations 'white-
              210x297', 'pink-210x297' and 'white-297x420', and not
              'pink-297x420'.

              If a collection contains a member "aaaI", whose syntax
              type is "text", the supported values would probably be
              defined by the definition of "xxx" rather than by the
              attribute "aaaI-supported".

      g) the default value of each "aaaI" member attribute if it is
         OPTIONAL for a client to supply the "aaa" member attribute in a
         request.  The default value is specified by the attribute's
         definition within a document and MUST be one of the following:

           i) a fixed default

          ii) a mechanism by which the Printer determines default

         iii) an indefinite default that is left to the implementation.

          iv) an attribute that the Printer uses to determine the
              default

   6. The default value of "xxx", if a client does not supply it.  The
      default value is specified by the attribute's definition within a
      document and MUST be one of the following:

      a) a fixed default

      b) a mechanism by which the Printer determines default

      c) an indefinite default that is left to the implementation

      d) a Printer attribute "xxx-default" which is a collection with
         the same member attributes as "xxx".  If optional member
         attributes are absent, the Printer uses the defaulting rules of
         item 5g) above.

   7. The "xxx-ready (1setOf collection)" attribute, if human
      intervention is required to make many of the supported values
      available.  For example, "media-col" is an attribute which has a
      "ready" attribute.  Most attributes do not have a "ready"
      attribute.








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<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a> Nested Collections</span>

   A member attribute may have a syntax type of 'collection' or '1setOf
   collection', in which case it is called a nested collection
   attribute.  The rules for a nested collection attribute are the same
   as for a collection attribute as specified in <a href="#section-3.1">section 3.1</a>.

<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a> Collection Attributes as Attributes in Operations</span>

<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a> General Rules</span>

   A collection value is like any other IPP/1.1 value, except that it is
   structured.  The rules for attributes with collection values are the
   same as for attributes of any other syntax type (see IPP/1.1), be
   they in any group of a request of a response.

<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a> Unsupported Values</span>

   The rules for returning an unsupported collection attribute are an
   extension to the current rules:

   1. If the entire collection attribute is unsupported, then the
      Printer returns just the collection attribute name with the
      'unsupported' out-of-band value (see the beginning of <a href="./rfc2911#section-4.1">[RFC2911]
      section&nbsp;4.1</a>) in the Unsupported Attributes Group.

   2. If a collection contains unrecognized, unsupported member
      attributes and/or conflicting values, the attribute returned in
      the Unsupported Group is a collection containing the unrecognized,
      unsupported member attributes, and/or conflicting values.  The
      unrecognized member attributes have an out-of-band value of
      'unsupported' (see the beginning of <a href="./rfc2911#section-4.1">[RFC2911] section&nbsp;4.1</a>).  The
      unsupported member attributes and conflicting values have their
      unsupported or conflicting values.

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a> Example definition of a collection attribute</span>

   In some printing environments, it is desirable to allow the client to
   select the media by its properties, e.g., weight, color, size, etc.,
   instead of by name.  In IPP/1.1 (see [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>]), the "media (type3
   keyword | name) Job Template attribute allows selection by name.  It
   is tempting to extend the "media" attribute syntax to include
   "collection", but then existing clients could not understand default
   or supported media values that use the collection value.  To preserve
   interoperability, a new attribute MUST BE added, e.g., "media-col
   (collection)".  The following subsections contain a sample definition
   of a simplified "media-col" attribute.  The definition follows the
   rules in <a href="#section-3">section 3</a>.



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   All of the example attribute definitions in this document are
   illustrative examples, rather than actual definitions.  These
   examples are intended to illustrate how to define collection
   attributes.  Other documents MUST define collection attributes for
   use in actual interchange.  Such definitions may be very similar to
   the examples in this document, since we attempted to pick useful
   examples.

   Note: we picked the name "media-col" because the name "media" is
   already in use.  Ordinarily the collection attribute would have a
   name like any other attribute and would not end in "col".

   The member attributes of "media-col" attribute ("media-color (type 3
   keyword)" and "media-size (collection)") both follow the naming rules
   of item 4a3 of <a href="#section-3">section 3</a>, i.e., the names are unique across the
   entire IPP attribute name space.  The member attributes of the
   "media-size (collection)" member attribute ("x-dimension
   (integer(0:MAX))" and "y-dimension (integer(0:MAX))") both follow the
   naming rules of item 4a2 of <a href="#section-3">section 3</a>, i.e., they potentially occur
   elsewhere in the IPP attribute name space.

<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a> media-col (collection)</span>

   The "media-col" (collection) attribute augments the IPP/1.1 [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>]
   "media" attribute.  This collection attribute enables a client end
   user to submit a list of media characteristics to the Printer.  When
   the client specifies media using the "media-col" collection
   attribute, the Printer object MUST match the requested media exactly.
   The 'collection' consists of the following member attributes:

                  Table 1 - "media-col" member attributes

        Attribute name  attribute syntax             request  Printer
                                                              Support

        media-color     type3 keyword | name (MAX)   MAY      MUST

        media-size      collection                   MUST     MUST

   The definitions for the member attributes is given in the following
   sub-sections:

<span class="h4"><a class="selflink" id="section-5.1.1" href="#section-5.1.1">5.1.1</a> media-color (type3 keyword | name(MAX)</span>

   This member attribute identifies the color of the media.  Valid
   values are 'red', 'white' and 'blue'.





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   The "media-color-supported" (1setOf (type3 keyword | name(MAX)))
   Printer attribute identifies the values of this "media-color" member
   attribute that the Printer supports, i.e., the colors supported.

   If the client omits this member attribute, the Printer determines the
   value in an implementation dependent manner.

<span class="h4"><a class="selflink" id="section-5.1.2" href="#section-5.1.2">5.1.2</a> media-size (collection)</span>

   This member attribute identifies the size of the media.  The
   'collection' consists of the member attributes shown in Table 2:

            Table 2 - "media-size" collection member attributes

        Attribute name    attribute syntax      request   Printer
                                                          Support

        x-dimension       integer (0:MAX)       MUST      MUST

        y-dimension       integer (0:MAX)       MUST      MUST

   The definitions for the member attributes are given in the following
   sub-sections:

<span class="h5"><a class="selflink" id="section-5.1.2.1" href="#section-5.1.2.1">5.1.2.1</a>  x-dimension (integer(0:MAX))</span>

   This attribute identifies the width of the media in inch units along
   the X axis.

<span class="h5"><a class="selflink" id="section-5.1.2.2" href="#section-5.1.2.2">5.1.2.2</a>  y-dimension (integer(0:MAX))</span>

   This attribute identifies the height of the media in inch units along
   the Y axis.

   The "media-size-supported" (1setOf collection) Printer attribute
   identifies the values of this "media-size" member attribute that the
   Printer supports, i.e., the size combinations supported.  The names
   of the member attributes are the same as the member attributes of the
   "media-size" collection attribute, namely "x-dimension", and "y-
   dimension", since they have the same attribute syntax and the same
   semantics.

<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a> media-col-default (collection)</span>

   The "media-col-default" Printer attribute specifies the media that
   the Printer uses, if any, if the client omits the "media-col" and
   "media".  Job Template attributes in the Job Creation operation and
   the PDL do not include a media specification.  The member attributes



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   are defined in Table 1.  A Printer MUST support the same member
   attributes for this default collection attribute as it supports for
   the corresponding "media-col" Job Template attribute.

<span class="h3"><a class="selflink" id="section-5.3" href="#section-5.3">5.3</a> media-col-ready (1setOf collection)</span>

   The "media-col-ready" Printer attribute identifies the media that are
   available for use without human intervention, i.e., the media that
   are ready to be used without human intervention.  The collection
   value MUST have all of the member attributes that are supported in
   Table 1.

<span class="h3"><a class="selflink" id="section-5.4" href="#section-5.4">5.4</a> media-col-supported (1setOf type2 keyword)</span>

   The "media-col-supported" Printer attribute identifies the keyword
   names of the member attributes supported in the "media-col"
   collection Job Template attribute, i.e., the keyword names of the
   member attributes in Table 1 that the Printer supports.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a> A Second Example Definition Of A Collection Attribute</span>

   All of the example attribute definitions in this document are
   illustrative examples, rather than actual definitions.  These
   examples are intended to illustrate how to define collection
   attributes.  Other documents MUST define collection attributes for
   use in actual interchange.  Such definitions may be very similar to
   the examples in this document, since we attempted to pick useful
   examples.

   In some printing environments, it is desirable to allow the client to
   select the media for the job start sheet.  The reason for not adding
   the 'collection' attribute syntax to the existing "job-sheets" Job
   Template attribute is the same as for "media".  Instead, a new Job
   Template attribute is introduced, e.g., "job-sheet-col (collection)".

   The member attributes of "job-sheet-col" attribute ("job-sheets (type
   3 keyword)" and "media (type3 keyword | name)") both follow the
   naming rules of item 4a1 of <a href="#section-3">section 3</a>, i.e., they reuse existing IPP
   attributes.  According to the rules, their supported values come from
   the existing IPP attributes: "job-sheets-supported" and "media-
   supported".  However, their default values do not come from "job-
   sheets-default" and "media-default", respectively.  Rather, the
   definition of "job-sheet-col" says that "job-sheets (type 3 keyword)"
   is required and if "media (type3 keyword | name)" is absent, the
   Printer uses the same media as the rest of the job uses.






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   If "job-sheet-col" attribute was defined to contain the member
   attribute "job-sheet-media (type3 keyword | name)" instead of "media
   (type3 keyword | name)", then the definition would also have to
   specify a "job-sheet-media-supported (1setOf (type3 keyword | name))"
   whose values would be independent of "media-supported (1setOf (type3
   keyword | name))" and would be set separately by a System
   Administrator.

   The actual text for the definition of the attribute is left as an
   exercise for the reader.

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a> Encoding</span>

   This section defines the additional encoding tags used according to
   [<a href="./rfc2910" title="&quot;Internet Printing Protocol/1.1: Encoding and Transport&quot;">RFC2910</a>] and gives an example of their use.  The encoding tags
   defined in this document MUST be used by all collection attributes
   defined in other documents.  However, the example of their use is
   illustrative only.

<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a> Additional tags defined for representing a collection attribute</span>
<span class="h3">    value</span>

   The 'collection' attribute syntax uses the tags defined in Table 3.

   Table 3 - Tags defined for encoding the 'collection' attribute syntax

        Tag name         Tag
                         value     Meaning

        begCollection    0x34      Begin the collection attribute value.

        endCollection    0x37      End the collection attribute value.

        memberAttrName   0x4A      The value is the name of the
                                   collection member attribute

   When encoding a collection attribute "xxx" that contains an attribute
   "aaa" and is not inside another collection, the encoding follows
   these rules:

   1. The beginning of the collection is indicated with a value tag that
      MUST be syntax type 'begCollection' (0x34) with a name length and
      Name field that represent the name of the collection attribute
      ("xxx") as with any attribute, followed by a value.  The Printer
      MAY ignore the value and its length MAY be 0.  In the future,
      however, this field MAY contain useful information, such as the
      collection name (cf. the name of a C struct).




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   2. Each member attribute is encoded as a sequence of two or more
      values that appear to be part of a single multi-valued attribute,
      i.e., 1setOf.  The first value after the 'begCollection' value has
      the attribute syntax, 'memberAttrName' (0x4A), and its value holds
      the name of the first member attribute (e.g., "aaa").  The second
      value holds the first member's attribute value, which can be of
      any attribute syntax, except 'memberAttrName' or 'endCollection'.
      If the first member's attribute value is multi-valued, the third
      value holds the second value of the first member's value.
      Otherwise, the third value holds the name of second member
      attribute (e.g., "bbb"), and its attribute syntax is
      'memberAttrName'.  In this case, the fourth member's value is the
      value of "bbb".

      Note that the technique of encoding a 'collection' as a '1setOf'
      makes it easy for a Printer that doesn't support a particular
      collection attribute (or the collection attribute syntax at all)
      to simply skip over the entire collection value.

   3. The end of the collection is indicated with a value tag that MUST
      be syntax type 'endCollection' (e.g., 0x37) and MAY have a zero
      name length and a zero value length.  In the future, this field
      MAY contain useful information, such as the collection name that
      matches the one in the 'begCollection' .

   4. It is valid to have a member attribute that is itself, a
      collection attribute, i.e., collections can be nested within
      collections.  This is represented by the occurrence of a member
      attribute that is of attribute syntax type 'begCollection'.  Such
      a collection is terminated by a matching 'endCollection'.  The
      name of such a member attribute is in the immediately preceding
      value, whose syntax type is 'memberAttrName'.

   5. It is valid for a collection attribute to be multi-valued, i.e.,
      have more than one collection value.  If the next attribute
      immediately following the 'endCollection' has a zero name length
      and a tag of 'begCollection', then the collection attribute is a
      multi-valued collection, as with any attribute.  This statement
      applies to collections within collections and collections that are
      not in collections.

<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a> Example encoding: "media-col" (collection)</span>

   The collection specified in <a href="#section-5">section 5</a> is used for the encoding
   example shown in Table 5.  The example also shows nested collections,
   since the "media-size" member attribute is a 'collection.  The
   encoding example represents a blue 4x6-index card and takes 216
   octets.  The Appendices contain more complex examples.



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   Additional examples have been included in the appendices.

   The overall structure of the two collection values can be pictorially
   represented as:

      "media-col" =
        {  "media-color" =  'blue';
           "media-size" =
           {    "x-dimension" = 6;
                "y-dimension" = 4
             }
        },

   The full encoding is in table 5.  A simplified view of the encoding
   looks like this:

           Table 4 - Overview Encoding of "media-col" collection

      Tag Value             Name                  Value

      begCollection         media-col             ""

      memberAttrName        ""                    media-color

      keyword               ""                    blue

      memberAttrName        ""                    media-size

      begCollection         ""                    ""

      memberAttrName        ""                    x-dimension

      integer               ""                    6

      memberAttrName        ""                    y-dimension

      integer               ""                    4

      endCollection         ""                    ""

      endCollection         ""                    ""










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           Table 5 - Example Encoding of "media-col" collection

      Octets       Symbolic Value  Protocol   comments
                                   field

      0x34         begCollection   value-tag  beginning of the "media-
                                              col" collection attribute

      0x0009                       name-      length of (collection)
                                   length     attribute name

      media-col    media-col       name       name of (collection)
                                              attribute

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "media-color"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of "media-color"
                                   length     keyword

      media-color  media-color     value      value is name of 1st
                                              member attribute


      0x44         keyword type    value-tag  keyword type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)








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      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0004                       value-
                                   length

      blue         blue            value      value of 1st member
                                              attribute


      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "media-size"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000A                       value-     length of "media-size"
                                   length     keyword

      media-size   media-size      value      Name of 2nd member
                                              attribute

      0x34         begCollection   value-tag  Beginning of the "media-
                                              size" collection attribute
                                              which is a sub-collection

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     collection attribute names
                                   length     have no value

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "x-dimension"








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      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of "x-dimension"
                                   length     keyword

      x-dimension  x-dimension     value      name of  1st sub-
                                              collection member
                                              attribute


      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0006                       value      value of  1st sub-
                                              collection member
                                              attribute

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "y-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of the "y-
                                   length     dimension" keyword








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      Octets       Symbolic Value  Protocol   comments
                                   field

      y-dimension  y-dimension     value      name of  2nd sub-
                                              collection member
                                              attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0004                       value      value of  2nd sub-
                                              collection member
                                              attribute

      0x37         endCollection   value-tag  end of the sub-collection

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x37         endCollection   value-tag  end of the 1st collection
                                              value in 1setOf

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf










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      Octets       Symbolic Value  Protocol   comments
                                   field

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a> Legacy issues</span>

   IPP 1.x Printers and Clients will gracefully ignore collections and
   its member attributes if it does not understand the collection.  The
   begCollection and endCollection elements each look like an attribute
   with an attribute syntax that the recipient doesn't support and so
   should ignore the entire attribute.  The individual member attributes
   and their values will look like a 1setOf values of the collection
   attribute, so that the Printer simply ignores the entire attribute
   and all of its values.  Returning unsupported attributes is also
   simple, since only the name of the collection attribute is returned
   with the 'unsupported' out-of-band value (see <a href="#section-4.2">section 4.2</a>).

<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a> IANA Considerations</span>

   The following table provides registration for the 'collection'
   attribute syntax defined in this document.  This is to be registered
   according to the procedures in <a href="./rfc2911">RFC 2911</a> <a href="./rfc2911#section-6.3">[RFC2911] section&nbsp;6.3</a>.

   Tag value:      Attribute Syntaxes:            Ref.      Section:
   collection                                     <a href="./rfc3382">RFC 3382</a>         3
     0x34          begCollection                  <a href="./rfc3382">RFC 3382</a>       7.1
     0x37          endCollection                  <a href="./rfc3382">RFC 3382</a>       7.1
     0x4A          memberAttrName                 <a href="./rfc3382">RFC 3382</a>       7.1

   The resulting attribute syntax registration will be published in the
   <a href="http://www.iana.org/assignments/ipp-registrations">http://www.iana.org/assignments/ipp-registrations</a> registry.

<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a> Internationalization Considerations</span>

   This attribute syntax by itself has no impact on
   internationalization.  However, the member attributes that are
   subsequently defined for use in a collection may have
   internationalization considerations, as may any attribute, according
   to [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>].




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<span class="h2"><a class="selflink" id="section-11" href="#section-11">11</a> Security Considerations</span>

   This attribute syntax causes no more security concerns than any other
   attribute syntax.  It is only the attributes that are subsequently
   defined, to use this or any other attribute syntax, that may have
   security concerns, depending on the semantics of the attribute,
   according to [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>].

<span class="h2"><a class="selflink" id="section-12" href="#section-12">12</a> References</span>

<span class="h3"><a class="selflink" id="section-12.1" href="#section-12.1">12.1</a> Normative References</span>

   [<a id="ref-RFC2910">RFC2910</a>] Herriot, R., Butler, S., Moore, P. and R. Turner, "Internet
             Printing Protocol/1.1: Encoding and Transport", <a href="./rfc2910">RFC 2910</a>,
             September 2000.

   [<a id="ref-RFC2911">RFC2911</a>] Isaacson, S., deBry, R., Hastings, T., Herriot, R. and P.
             Powell, "Internet Printing Protocol/1.1: Model and
             Semantics", <a href="./rfc2911">RFC 2911</a>, September 2000.

<span class="h3"><a class="selflink" id="section-12.2" href="#section-12.2">12.2</a> Informative References</span>

   [<a id="ref-RFC2565">RFC2565</a>] Herriot, R., Butler, S., Moore, P. and R. Tuner, "Internet
             Printing Protocol/1.0: Encoding and Transport", <a href="./rfc2565">RFC 2565</a>,
             April 1999.

   [<a id="ref-RFC2566">RFC2566</a>] deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P.
             Powell, "Internet Printing Protocol/1.0: Model and
             Semantics", <a href="./rfc2566">RFC 2566</a>, April 1999.

   [<a id="ref-RFC2567">RFC2567</a>] Wright, D., "Design Goals for an Internet Printing
             Protocol", <a href="./rfc2567">RFC 2567</a>, April 1999.

   [<a id="ref-RFC2568">RFC2568</a>] Zilles, S., "Rationale for the Structure and Model and
             Protocol for the Internet Printing Protocol", <a href="./rfc2568">RFC 2568</a>,
             April 1999.

   [<a id="ref-RFC2569">RFC2569</a>] Herriot, R., Hastings, T., Jacobs, N. and J. Martin,
             "Mapping between LPD and IPP Protocols", <a href="./rfc2569">RFC 2569</a>, April
             1999.

   [<a id="ref-RFC2616">RFC2616</a>] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,
             L., Leach, P. and T. Berners-Lee, "Hypertext Transfer
             Protocol - HTTP/1.1", <a href="./rfc2616">RFC 2616</a>, June 1999.

   [<a id="ref-RFC3196">RFC3196</a>] Hastings, T., Manros, C., Zehler, P., Kugler, C. and H.
             Holst, "Internet Printing Protocol/1.1: Implementor's
             Guide", <a href="./rfc3196">RFC 3196</a>, November 2001.



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Appendix A: Encoding Example of a Simple Collection (Informative)

   The overall structure of the collection value can be pictorially
   represented as:

      "media-size" =
        {  "x-dimension" = 6;
           "y-dimension" = 4
        }

   A simplified view of the encoding would look like this:

             Table 6 - Overview Encoding of simple collection

      Tag Value             Name                  Value

      begCollection         media-size            ""

      memberAttrName        ""                    x-dimension

      integer               ""                    6

      memberAttrName        ""                    y-dimension

      integer               ""                    4

      endCollection         ""                    ""

      Note: "" represents a name or value whose length is 0.

              Table 7 - Example Encoding of simple collection

      Octets       Symbolic Value  Protocol   comments
                                   field

      0x34         begCollection   value-tag  beginning of the "media-
                                              size" collection attribute

      0x000A                       name-      length of (collection)
                                   length     attribute name

      media-size   media-size      name       name of (collection)
                                              attribute








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      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts member attribute:
                                              "x-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of "x-dimension"
                                   length     keyword

      x-dimension  x-dimension     value      name of  1st collection
                                              member attribute


      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0006                       value      value of  1st collection
                                              member attribute

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "y-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)




<span class="grey">deBry, et. al.              Standards Track                    [Page 23]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-24" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


      Octets       Symbolic Value  Protocol   comments
                                   field

      0x000B                       value-     length of the "y-
                                   length     dimension" keyword

      y-dimension  y-dimension     value      name of  2nd collection
                                              member attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf for
                                   length     media-size

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0004                       value      value of  2nd collection
                                              member attribute

      0x37         endCollection   value-tag  end of the collection

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)















<span class="grey">deBry, et. al.              Standards Track                    [Page 24]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-25" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


Appendix B: Encoding Example of 1setOf Collection (Informative)

   The overall structure of the collection value can be pictorially
   represented as:

      "media-size-supported" =
        {  "x-dimension" = 6;
           "y-dimension" = 4
        },
        {  "x-dimension" = 3;
           "y-dimension" = 5
        };

   A simplified view of the encoding would look like this:

             Table 8 - Overview Encoding of 1setOf collection

      Tag Value              Name                 Value

      begCollection          media-size-          ""
                             supported

      memberAttrName         ""                   x-dimension

      integer                ""                   6

      memberAttrName         ""                   y-dimension

      integer                ""                   4

      endCollection          ""                   ""

      begCollection          ""                   ""

      memberAttrName         ""                   x-dimension

      integer                ""                   3

      memberAttrName         ""                   y-dimension

      integer                ""                   5

      endCollection          ""                   ""








<span class="grey">deBry, et. al.              Standards Track                    [Page 25]</span></pre>
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<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


              Table 9 - Example Encoding of 1setOf collection

      Octets       Symbolic Value  Protocol   comments
                                   field

      0x34         begCollection   value-tag  beginning of the "media-
                                              size-supported (1setOf
                                              collection" attribute

      0x00014                      name-      length of (collection)
                                   length     attribute name

      media-size-  media-size-     name       name of (collection)
      supported    supported                  attribute

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts member attribute:
                                              "x-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of "x-dimension"
                                   length     keyword

      x-dimension  x-dimension     value      name of  1st collection
                                              member attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)








<span class="grey">deBry, et. al.              Standards Track                    [Page 26]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-27" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0004                       value-     length of an integer = 4
                                   length

      0x0006                       value      value of  1st collection
                                              member attribute

      0x4A         memberAttrName  value-tag  starts member attribute:
                                              "y-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of the "y-
                                   length     dimension" keyword

      y-dimension  y-dimension     value      name of  2nd collection
                                              member attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0004                       value      value of  2nd collection
                                              member attribute

      0x37         endCollection   value-tag  end of the collection

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)






<span class="grey">deBry, et. al.              Standards Track                    [Page 27]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-28" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x34         begCollection   value-tag  beginning of the 2nd
                                              member of the 1setOf
                                              "sizes-avail " collection
                                              attribute

      0x0000                       name-      Zero length name indicates
                                   length     this is member of previous
                                              attribute

                                   name       no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts member attribute:
                                              "x-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of "x-dimension"
                                   length     keyword

      x-dimension  x-dimension     value      name of  1st collection
                                              member attribute

      0x21         integer type    value-tag  attribute type








<span class="grey">deBry, et. al.              Standards Track                    [Page 28]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-29" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0003                       value      value of  1st collection
                                              member attribute

      0x4A         memberAttrName  value-tag  starts member attribute:
                                              "y-dimension"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x000B                       value-     length of the "y-
                                   length     dimension" keyword

      y-dimension  y-dimension     value      name of  2nd collection
                                              member attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0005                       value      value of  2nd collection
                                              member attribute








<span class="grey">deBry, et. al.              Standards Track                    [Page 29]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-30" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


      Octets       Symbolic Value  Protocol   comments
                                   field

      0x37         endCollection   value-tag  end of the 1setOf
                                              collection value

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)


































<span class="grey">deBry, et. al.              Standards Track                    [Page 30]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-31" ></span>
<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


Appendix C: Encoding Example of Collection containing 1setOf XXX
            attribute (Informative)

   The overall structure of the collection value can be pictorially
   represented as:

      "wagons" =
        {  "colors" = red, blue;
           "sizes" = 4, 6, 8
        }

   A simplified view of the encoding would look like this:

       Table 10 - Overview Encoding of collection with 1setOf value

            Tag Value                Name                Value

            begCollection            wagons              ""

            memberAttrName           ""                  colors

            keyword                  ""                  red

            keyword                  ""                  blue

            memberAttrName           ""                  sizes

            integer                  ""                  4

            integer                  ""                  6

            integer                  ""                  8

            endCollection            ""                  ""

















<span class="grey">deBry, et. al.              Standards Track                    [Page 31]</span></pre>
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<span class="grey"><a href="./rfc3382">RFC 3382</a>         IPP: The 'collection' attribute syntax   September 2002</span>


        Table 11 - Example Encoding of collection with 1setOf value

      Octets       Symbolic Value  Protocol   comments
                                   field

      0x34         begCollection   value-tag  beginning of the "wagons"
                                              collection attribute

      0x0005                       name-      length of (collection)
                                   length     attribute name

      wagons       wagons          name       name of (collection)
                                              attribute

      0x0000                       value-     defined to be 0 for this
                                   length     type

                                              no value (since value-
                                              length was 0)

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "colors"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0006                       value-     length of "colors" keyword
                                   length

      colors       colors          value      value is name of 1st
                                              member attribute

      0x44         keyword type    value-tag  keyword type

      0x0000                       name-      0 indicates 1setOf wagons
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-
                                   length






<span class="grey">deBry, et. al.              Standards Track                    [Page 32]</span></pre>
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      Octets       Symbolic Value  Protocol   comments
                                   field

      blue         blue            value      value of 1st member
                                              attribute

      0x44         keyword type    value-tag  keyword type

      0x0000                       name-      0 indicates 1setOf wagons
                                   length

                                              no name (since name-length
                                              was 0)

      0x0003                       value-
                                   length

      red          red             value      value of 1st member
                                              attribute

      0x4A         memberAttrName  value-tag  starts a new member
                                              attribute: "sizes"

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0005                       value-     length of "length-avail"
                                   length     keyword

      sizes        sizes           value      Name of 2nd member
                                              attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf wagons
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length






<span class="grey">deBry, et. al.              Standards Track                    [Page 33]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-34" ></span>
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      Octets       Symbolic Value  Protocol   comments
                                   field

      0x0004                       value      1st value for 1setOf
                                              integer attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-
                                   length     length of an integer = 4

      0x0006                       value      2nd value for 1setOf
                                              integer attribute

      0x21         integer type    value-tag  attribute type

      0x0000                       name-      0 indicates 1setOf
                                   length

                                              no name (since name-length
                                              was 0)

      0x0004                       value-     length of an integer = 4
                                   length

      0x0008                       value      3rd  value for 1setOf
                                              integer attribute

      0x37         endCollection   value-tag  end of the collection

      0x0000                       name-      defined to be 0 for this
                                   length     type, so part of 1setOf

                                              no name (since name-length
                                              was 0)

      0x0000                       value-     defined to be 0 for this
                                   length     type







<span class="grey">deBry, et. al.              Standards Track                    [Page 34]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-35" ></span>
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      Octets       Symbolic Value  Protocol   comments
                                   field

                                              no value (since value-
                                              length was 0)

Appendix D: Description of the Base IPP Documents (Informative)

   The base set of IPP documents includes:

      Design Goals for an Internet Printing Protocol [<a href="./rfc2567" title="&quot;Design Goals for an Internet Printing Protocol&quot;">RFC2567</a>]
      Rationale for the Structure and Model and Protocol for the
      Internet Printing Protocol [<a href="./rfc2568" title="&quot;Rationale for the Structure and Model and Protocol for the Internet Printing Protocol&quot;">RFC2568</a>]
      Internet Printing Protocol/1.1: Model and Semantics [<a href="./rfc2911" title="&quot;Internet Printing Protocol/1.1: Model and Semantics&quot;">RFC2911</a>]
      Internet Printing Protocol/1.1: Encoding and Transport [<a href="./rfc2910" title="&quot;Internet Printing Protocol/1.1: Encoding and Transport&quot;">RFC2910</a>]
      Internet Printing Protocol/1.1: Implementer's Guide [<a href="./rfc3196" title="&quot;Internet Printing Protocol/1.1: Implementor's Guide&quot;">RFC3196</a>]
      Mapping between LPD and IPP Protocols [<a href="./rfc2569" title="&quot;Mapping between LPD and IPP Protocols&quot;">RFC2569</a>]

   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, <a href="./rfc2565">RFC2565</a>].  A few OPTIONAL operator
   operations have been added to IPP/1.1 [RFC2911, <a href="./rfc2910">RFC2910</a>].

   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
   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 [<a href="./rfc2616" title="&quot;Hypertext Transfer Protocol - HTTP/1.1&quot;">RFC2616</a>].  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.



<span class="grey">deBry, et. al.              Standards Track                    [Page 35]</span></pre>
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   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.

Authors' Addresses

   Roger deBry
   Utah Valley State College
   Orem, UT 84058

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


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

   Phone: 310-333-6413
   Fax: 310-333-5514
   EMail: hastings@cp10.es.xerox.com


   Robert Herriot
   Consultant
   706 Colorado Ave
   Palo Alto, CA 94303

   Phone: 650-327-4466
   Fax: 650-327-4466
   EMail: bob@herriot.com











<span class="grey">deBry, et. al.              Standards Track                    [Page 36]</span></pre>
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   Kirk Ocke
   Xerox Corp.
   800 Phillips Rd
   M/S 128-30E
   Webster, NY 14580

   Phone: (585) 442-4832
   EMail: KOcke@crt.xerox.com


   Peter Zehler
   Xerox Corp.
   800 Phillips Rd
   M/S 128-30E
   Webster, NY 14580

   Phone: (585) 265-8755
   EMail: PZehler@crt.xerox.com

   IPP Web Page:  <a href="http://www.pwg.org/ipp/IPP">http://www.pwg.org/ipp/</a>
   <a href="http://www.pwg.org/ipp/IPP">IPP</a> 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.














<span class="grey">deBry, et. al.              Standards Track                    [Page 37]</span></pre>
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Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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.

   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.



















deBry, et. al.              Standards Track                    [Page 38]
</pre>