INTERNET-DRAFT Roger deBry
<draft-ietf-ipp-collection-03.txt> Utah Valley State College
T. Hastings
Xerox Corporation
R. Herriot
Xerox Corporation
K. Ocke
Xerox Corporation
P. Zehler
Xerox Corporation
June 29, 2000
Internet Printing Protocol (IPP):
The 'collection' attribute syntax
Copyright (C) The Internet Society (2000). 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
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Abstract
This document specifies an OPTIONAL attribute syntax called
'collection' for use with the Internet Printing Protocol/1.0
(IPP) [RFC2565, RFC2566], IPP/1.1 [ipp-mod, ipp-pro], and
subsequent versions. 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.
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The full 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 (this document)
Internet Printing Protocol/1.1: Encoding and Transport [IPP-PRO]
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. A few OPTIONAL operator operations have been
added to IPP/1.1.
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
working group's major decisions.
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 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 a
new scheme named 'ipp' 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.
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Table of Contents
1 Problem Statement.................................................5
2 Solution..........................................................5
3 Definition of a Collection Attribute..............................6
3.1 Information to Include.........................................6
3.2 Nested Collections.............................................9
4 Collection Attributes as Attributes in Operations.................9
4.1 General Rules..................................................9
4.2 Unsupported Values.............................................9
5 Example definition of a collection attribute.....................10
5.1 media-col (collection)........................................10
5.1.1media-color (type3 keyword | name(MAX)......................11
5.1.2media-size (collection).....................................11
5.2 media-col-default (collection)................................12
5.3 media-col-ready (1setOf collection)...........................12
5.4 media-col-supported (1setOf type2 keyword)....................12
6 A Second Example Definition Of A Collection Attribute............12
7 Encoding.........................................................13
7.1 Additional tags defined for representing a collection attribute
value..............................................................13
7.2 Example encoding: "media-col" (collection)....................14
8 Legacy issues....................................................17
9 IANA Considerations..............................................18
10 Internationalization Considerations..............................18
11 Security Considerations..........................................18
12 References.......................................................18
13 Author's Addresses...............................................19
14 Appendix A: Encoding Example of a Simple Collection..............20
15 Appendix B: Encoding Example of 1setOf Collection................22
16 Appendix C: Encoding Example of Collection containing 1setOf XXX
attribute............................................................26
17 Appendix D: Full Copyright Statement.............................28
Table of Tables
Table 1 - "media-col" member attributes..............................11
Table 2 - "media-size" collection member attributes..................11
Table 3 - Tags defined for encoding the 'collection' attribute syntax13
Table 4 - Overview Encoding of "media-col" collection................15
Table 5 - Example Encoding of "media-col" collection.................15
Table 6 - Overview Encoding of simple collection.....................21
Table 7 - Example Encoding of simple collection......................21
Table 8 - Overview Encoding of 1setOf collection.....................23
Table 9 - Example Encoding of 1setOf collection......................23
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Table 10 - Overview Encoding of collection with 1setOf value.........26
Table 11 - Example Encoding of collection with 1setOf value..........26
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1 Problem Statement
The IPP Model and Semantics [ipp-mod] 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 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 [ipp-pro]). Current 1.0 and 1.1
parsers that don't support the 'collection' mechanism must not confuse
collections or parts of collection they receive with other attributes.
2 Solution
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-value (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 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 section 3.1would 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 section 3.1.
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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 contains 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
section 13.1.4.1), or (2) accept the request and use only one of each
duplicate member attribute..
3 Definition of a Collection Attribute
This section describes the requirements for any collection attribute
definition.
3.1 Information to Include
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.
4. An "xxx-supported" attribute MUST be specified and it has one of
the following two forms:
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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 supported
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 unique be across
the entire IPP attribute name space.
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
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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 the 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 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 in 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
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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 in 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". Though optional member
attributes may be absent in which case 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.
3.2 Nested Collections
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 section 3.1.
4 Collection Attributes as Attributes in Operations
4.1 General Rules
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.
4.2 Unsupported Values
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 [ipp-mod]
section 4.1) in the Unsupported Attributes Group.
2. If a collection contains unrecognized, unsupported member
attributes and/or conflicting values, the attribute returned in
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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 [ipp-mod] section
4.1). The unsupported member attributes and conflicting values
have their unsupported or conflicting values.
5 Example definition of a collection attribute
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 [ipp-mod]), 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
section 3.
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 section 3, 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
section 3, i.e. they potentially occur elsewhere in the IPP attribute
name space.
5.1 media-col (collection)
The "media-col" (collection) attribute augments the IPP/1.1 [ipp-mod]
"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:
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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:
5.1.1 media-color (type3 keyword | name(MAX)
This member attribute identifies the color of the media. Valid
values are 'red', 'white' and 'blue'
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.
5.1.2 media-size (collection)
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 attribute syntax request Printer
name Support
x-dimension integer (0:MAX) MUST MUST
y-dimension integer (0:MAX) MUST MUST
The definitions for the member attributes is given in the
following sub-sections:
5.1.2.1 x-dimension (integer(0:MAX))
This attribute identifies the width of the media in inch units
along the X axis.
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5.1.2.2 y-dimension (integer(0:MAX))
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.
5.2 media-col-default (collection)
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 attribute in the Job Creation operation (and the PDL
doesn't include a media specification). The member attributes 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.
5.3 media-col-ready (1setOf collection)
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.
5.4 media-col-supported (1setOf type2 keyword)
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.
6 A Second Example Definition Of A Collection Attribute
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 section 3, 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-
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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.
If "job-sheet-col" attribute were 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.
7 Encoding
This section defines the additional encoding tags used according to
[ipp-pro] and gives an example of their use.
7.1 Additional tags defined for representing a collection attribute
value
The 'collection' attribute syntax uses the tags defined in Table 3.
Table 3 - Tags defined for encoding the 'collection' attribute syntax
Tag name Tag Meaning
value
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 of 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).
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
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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.
7.2 Example encoding: "media-col" (collection)
The collection specified in section 5is 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 cards and takes 216 octets. The Appendices
contains more complex examples.
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;
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"y-dimension" = 4
}
},
The full encoding is in table 4. 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 "" ""
Table 5 - Example Encoding of "media-col" collection
Octets Symbolic Protocol comments
Value 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 memberAttrNam value-tag starts a new member
e 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
st
media-color media-color value value is name of 1 member
attribute
0x44 keyword type value-tag keyword type
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Octets Symbolic Protocol comments
Value field
0x0000 name- 0 indicates 1setOf
length
no name (since name-length
was 0)
0x0004 value-
length
st
blue blue value value of 1 member
attribute
0x4A memberAttrNam value-tag starts a new member
e 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
nd
media-size media-size value Name of 2 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 memberAttrNam value-tag starts a new member
e 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
st
x-dimension x-dimension value name of 1 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
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Octets Symbolic Protocol comments
Value field
st
0x0006 value value of 1 sub-
collection member attribute
0x4A memberAttrNam value-tag starts a new member
e 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-dimension"
length keyword
nd
y-dimension y-dimension value name of 2 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
nd
0x0004 value value of 2 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
no name (since name-length
was 0)
0x0000 value- defined to be 0 for this
length type
no value (since value-
length was 0)
8 Legacy issues
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
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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 section 4.2).
9 IANA Considerations
This attribute syntax will be registered with IANA after the WG approves
its specification according to the procedures for extension of the
IPP/1.1 Model and Semantics [ipp-mod].
10 Internationalization Considerations
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 [ipp-mod].
11 Security Considerations
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
[ipp-mod].
12 References
[ipp-mod]
Isaacson, S., deBry, R., Hastings, T., Herriot, R., Powell, P.,
"Internet Printing Protocol/1.1: Model and Semantics" draft-ietf-
ipp-model-v11-06.txt, March 1, 2000.
[ipp-ntfy]
Isaacson, S., Martin, J., deBry, R., Hastings, T., Shepherd, M.,
Bergman, R. " Internet Printing Protocol/1.0 & 1.1: IPP Event
Notification Specification" draft-ietf-ipp-not-spec-02.txt, work in
progress, February 2, 2000.
[ipp-pro]
Herriot, R., Butler, S., Moore, P., Turner, R., "Internet Printing
Protocol/1.1: Encoding and Transport", draft-ietf-ipp-protocol-v11-
05.txt, March 1, 2000.
[RFC2565]
Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet Printing
Protocol/1.0: Encoding and Transport", RFC 2565, April 1999.
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INTERNET-DRAFT IPP: The 'collection' attribute syntax June 29, 2000
[RFC2566]
R. deBry, T. Hastings, R. Herriot, S. Isaacson, P. Powell,
"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.
[RFC2616]
R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P.
Leach, T. Berners-Lee, "Hypertext Transfer Protocol - HTTP/1.1",
RFC 2616, June 1999.
13 Author's 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
e-mail: hastings@cp10.es.xerox.com
Robert Herriot
Xerox Corp.
3400 Hill View Ave, Building 1
Palo Alto, CA 94304
Phone: 650-813-7696
Fax: 650-813-6860
e-mail: robert.herriot@pahv.xerox.com
Kirk Ocke
Xerox Corp.
800 Phillips Rd
M/S 139-05A
Webster, NY 14580
Phone: (716) 442-4832
EMail: kirk.ocke@usa.xerox.com
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Peter Zehler
Xerox Corp.
800 Phillips Rd
M/S 139-05A
Webster, NY 14580
Phone: (716) 265-8755
EMail: peter.zehler@usa.xerox.com
14 Appendix A: Encoding Example of a Simple Collection
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:
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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 Protocol comments
Value 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
0x0000 value- defined to be 0 for this
length type
no value (since value-
length was 0)
0x4A memberAttrNam value-tag starts member attribute:
e "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
st
x-dimension x-dimension value name of 1 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
st
0x0006 value value of 1 collection
member attribute
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Octets Symbolic Protocol comments
Value field
0x4A memberAttrNam value-tag starts a new member
e 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-dimension"
length keyword
nd
y-dimension y-dimension value name of 2 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
nd
0x0004 value value of 2 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)
15 Appendix B: Encoding Example of 1setOf Collection
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:
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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 "" ""
Table 9 - Example Encoding of 1setOf collection
Octets Symbolic Protocol comments
Value 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 memberAttrNam value-tag starts member attribute:
e "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
st
x-dimension x-dimension value name of 1 collection
member attribute
0x21 integer type value-tag attribute type
0x0000 name- 0 indicates 1setOf
length
no name (since name-length
was 0)
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Octets Symbolic Protocol comments
Value field
0x0004 value- length of an integer = 4
length
st
0x0006 value value of 1 collection
member attribute
0x4A memberAttrNam value-tag starts member attribute:
e "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-dimension"
length keyword
nd
y-dimension y-dimension value name of 2 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
nd
0x0004 value value of 2 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)
nd
0x34 begCollection value-tag beginning of the 2 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 memberAttrNam value-tag starts member attribute:
e "x-dimension"
0x0000 name- defined to be 0 for this
length type, so part of 1setOf
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Octets Symbolic Protocol comments
Value field
no name (since name-length
was 0)
0x000B value- length of "x-dimension"
length keyword
st
x-dimension x-dimension value name of 1 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
st
0x0003 value value of 1 collection
member attribute
0x4A memberAttrNam value-tag starts member attribute:
e "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-dimension"
length keyword
nd
y-dimension y-dimension value name of 2 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
nd
0x0005 value value of 2 collection
member attribute
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)
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16 Appendix C: Encoding Example of Collection containing 1setOf XXX
attribute
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 "" ""
Table 11 - Example Encoding of collection with 1setOf value
Octets Symbolic Protocol comments
Value 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 memberAttrNam value-tag starts a new member
e 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
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Octets Symbolic Protocol comments
Value field
st
colors colosr value value is name of 1 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
st
blue blue value value of 1 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
st
red red value value of 1 member
attribute
0x4A memberAttrNam value-tag starts a new member
e 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
nd
sizes sizes value Name of 2 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
st
0x0004 value 1 value for 1SetOf
integer attribute
0x21 integer type value-tag attribute type
0x0000 name- 0 indicates 1setOf
length
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Octets Symbolic Protocol comments
Value field
no name (since name-length
was 0)
0x0004 value- length of an integer = 4
length
nd
0x0006 value 2 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
rd
0x0008 value 3 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
no value (since value-
length was 0)
17 Appendix D: Full Copyright Statement
Copyright (C) The Internet Society (1998,1999,2000). 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.
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