< draft-ietf-conneg-feature-type-02.txt   draft-ietf-conneg-feature-type-03.txt >
IETF conneg working group Graham Klyne IETF conneg working group Graham Klyne
Internet draft Content Technologies Internet draft Content Technologies
Category: Work-in-progress 30 November 1999 Category: Work-in-progress 4 April 2000
Expires: May 2000 Expires: October 2000
MIME content types in media feature expressions MIME content types in media feature expressions
<draft-ietf-conneg-feature-type-02.txt> <draft-ietf-conneg-feature-type-03.txt>
Status of this memo Status of this memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026. all provisions of Section 10 of RFC 2026.
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society 1999. All Rights Reserved. Copyright (C) The Internet Society 2000. All Rights Reserved.
Abstract Abstract
In RFC 2533, "A syntax for describing media feature sets", an In "A syntax for describing media feature sets", an expression
expression format is presented for describing media feature format is presented for describing media feature capabilities using
capabilities using simple media feature tags. simple media feature tags.
This memo defines a media feature tag whose value is a MIME content This memo defines a media feature tag whose value is a MIME content
type. This allows the construction of feature expressions that type. This allows the construction of feature expressions that
take account of the MIME content type of the corresponding data. take account of the MIME content type of the corresponding data.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
Table of contents Table of contents
1. Introduction ............................................2 1. Introduction ............................................2
1.1 Terminology and document conventions 2 1.1 Terminology and document conventions 2
1.2 Discussion of this document 3 1.2 Discussion of this document 3
2. Motivation and goals ....................................4 2. Motivation and goals ....................................4
3. MIME content type feature tag ...........................4 3. MIME content type feature tag ...........................4
4. Examples ................................................5 4. Examples ................................................5
4.1 Simple text 5 4.1 Simple text 5
4.2 Fax image 5 4.2 Fax image 5
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This section defines a number of terms and other document This section defines a number of terms and other document
conventions, which are used with specific meaning in this memo. conventions, which are used with specific meaning in this memo.
media feature media feature
information that indicates facilities assumed to be information that indicates facilities assumed to be
available for the message content to be properly rendered available for the message content to be properly rendered
or otherwise presented. Media features are not intended or otherwise presented. Media features are not intended
to include information that affects message transmission. to include information that affects message transmission.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
feature set feature set
some set of media features described by a media feature some set of media features described by a media feature
assertion, as described in "A syntax for describing media assertion, as described in "A syntax for describing media
feature sets" [1]. (See that memo for a more formal feature sets" [1]. (See that memo for a more formal
definition of this term.) definition of this term.)
feature set expression feature set expression
a string that describes some feature set, formulated a string that describes some feature set, formulated
according to the rules in "A syntax for describing media according to the rules in "A syntax for describing media
feature sets" [1] (and possibly extended by other feature sets" [1] (and possibly extended by other
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ietf-medfree@imc.org ietf-medfree@imc.org
To subscribe to this list, send a message with the body 'subscribe' To subscribe to this list, send a message with the body 'subscribe'
to "ietf-medfree-request@imc.org". to "ietf-medfree-request@imc.org".
To see what has gone on before you subscribed, please see the To see what has gone on before you subscribed, please see the
mailing list archive at: mailing list archive at:
http://www.imc.org/ietf-medfree/ http://www.imc.org/ietf-medfree/
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
2. Motivation and goals 2. Motivation and goals
The media feature expression syntax [1] and feature tags [2] were The media feature expression syntax [1] and feature tags [2] were
designed with a view to providing content media information that designed with a view to providing content media information that
augments basic MIME content type information. There are some augments basic MIME content type information. There are some
situations where it is useful to be able include that content type situations where it is useful to be able include that content type
information in a media feature expression: information in a media feature expression:
o Media feature details may depend upon the content type being o Media feature details may depend upon the content type being
used. The media feature combining algebra and syntax [1] cannot used. The media feature combining algebra and syntax [1] cannot
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o When media features are used to describe a message content, they o When media features are used to describe a message content, they
may refer to inner parts of a MIME composite; e.g. the component may refer to inner parts of a MIME composite; e.g. the component
parts of a 'multipart', files in a compressed archive, or parts of a 'multipart', files in a compressed archive, or
encrypted message data. encrypted message data.
3. MIME content type feature tag 3. MIME content type feature tag
Feature tag name Legal values Feature tag name Legal values
---------------- ------------ ---------------- ------------
type <string> type <string>
containing any MIME content type value. containing a MIME content-type value.
Reference: this document, appendix A. Reference: this document, appendix A.
The 'type' feature tag indicates a MIME media content type (i.e. The 'type' feature tag indicates a MIME media content type (i.e.
that appears in a 'Content-type:' header in the corresponding MIME- that appears in a 'Content-type:' header of the corresponding MIME-
formatted data). formatted data). It must be a string of the form "type/subtype",
where 'type' and 'subtype' are defined by the MIME specification
[7]. Only lower-case letters should be used.
The media type should be given without any parameter values. The The content type must be given without any content-type parameter
intention here is that information that is conveyed in MIME content values.
type parameters is more usefully handled in a media feature
expression by separate feature tags.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999 To include information in media feature expressions that is
otherwise conveyed in a MIME content-type parameter, a separate
media feature tag should be registered [2] and used in the media
feature expression. This is illustrated by the use of 'charset' in
the example at 4.1 below -- the 'charset' tag is defined by a
separate registration [10].
NOTE: content type parameters in a 'type' value are NOTE: Allowing content-type parameters to be part of a
strongly discouraged, but not prohibited. In deciding type tag value was considered, but rejected because of
whether or not to include a parameter value, implementers concerns about canonicalization, ordering, case
should bear in mind the feature set matching rules [1]. sensitivity, etc. Only exact, case-sensitive, character
These would cause 'type' values with and without matching is defined for media feature expressions [1].
parameters to be treated as completely distinct values,
which may lead to unexpected results.
4. Examples 4. Examples
4.1 Simple text 4.1 Simple text
(& (type="text/plain") (charset=US-ASCII) (& (type="text/plain") (charset=US-ASCII)
(color=binary) (paper-size=A4) ) (color=binary) (paper-size=A4) )
4.2 Fax image 4.2 Fax image
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(ua-terminal=mobile-handset) (ua-terminal=mobile-handset)
(audio-channels=1) ) (audio-channels=1) )
NOTE: in this case, some media features apply to MIME NOTE: in this case, some media features apply to MIME
parts contained within the declared 'multipart/voice- parts contained within the declared 'multipart/voice-
message' content type. The goal here is not so much to message' content type. The goal here is not so much to
mirror the MIME structure as to convey useful information mirror the MIME structure as to convey useful information
about the (possible) message content. about the (possible) message content.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
4.4 Web browser capabilities 4.4 Web browser capabilities
(& (pix-x<=800) (pix-y<=600) (& (pix-x<=800) (pix-y<=600)
(| (& (type="text/html") (charset=iso-8859-1) (color=limited)) (| (& (type="text/html") (charset=iso-8859-1)
(color=limited) )
(& (type="text/plain") (charset=US-ASCII) ) (& (type="text/plain") (charset=US-ASCII) )
(& (type="image/gif") (color=mapped)) (& (type="image/gif") (color=mapped))
(& (type="image/jpeg") (color=full) ) ) ) (& (type="image/jpeg") (color=full) ) ) )
This example describes an HTML viewer that can deal with a limited This example describes an HTML viewer that can deal with a limited
number of color text tags, a gif viewer that supports mapped color, number of color text tags, a gif viewer that supports mapped color,
and a jpeg viewer that supports color. and a jpeg viewer that supports color.
5. IANA considerations 5. IANA considerations
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expressions [1,2]. expressions [1,2].
7. Acknowledgements 7. Acknowledgements
This proposal draws from discussions in the IETF 'conneg' working This proposal draws from discussions in the IETF 'conneg' working
group. The voice message example is based on some ideas by Glen group. The voice message example is based on some ideas by Glen
Parsons. Parsons.
The author would like to thank the following people who offered The author would like to thank the following people who offered
comments that led to significant improvements: Ted Hardie, Larry comments that led to significant improvements: Ted Hardie, Larry
Masinter, Paul Hoffman, Jacob Palme. Masinter, Paul Hoffman, Jacob Palme, Ned Freed.
8. References 8. References
[1] RFC 2533, "A syntax for describing media feature sets" [1] RFC 2533, "A syntax for describing media feature sets"
Graham Klyne, 5GM/Content Technologies Graham Klyne, 5GM/Content Technologies
March 1999. March 1999.
Internet draft MIME content types in media feature expressions
[2] RFC 2506, "Media Feature Tag Registration Procedure" [2] RFC 2506, "Media Feature Tag Registration Procedure"
Koen Holtman, TUE Koen Holtman, TUE
Andrew Mutz, Hewlett-Packard Andrew Mutz, Hewlett-Packard
Ted Hardie, NASA Ted Hardie, NASA
March 1999. March 1999.
Internet draft MIME content types in media feature expressions
30 November 1999
[3] RFC 2234, "Augmented BNF for Syntax Specifications: ABNF" [3] RFC 2234, "Augmented BNF for Syntax Specifications: ABNF"
D. Crocker (editor), Internet Mail Consortium D. Crocker (editor), Internet Mail Consortium
P. Overell, Demon Internet Ltd. P. Overell, Demon Internet Ltd.
November 1997. November 1997.
[4] RFC 2068, "Hyptertext Transfer Protocol -- HTTP/1.1" [4] RFC 2068, "Hyptertext Transfer Protocol -- HTTP/1.1"
R. Fielding, UC Irvine R. Fielding, UC Irvine
J. Gettys, J. Gettys,
J. Mogul, DEC J. Mogul, DEC
H. Frytyk, H. Frytyk,
T. Berners-Lee, MIT/LCS T. Berners-Lee, MIT/LCS
January 1997. January 1997.
(Non-normative)
[5] RFC 2295, "Transparent Content Negotiation in HTTP" [5] RFC 2295, "Transparent Content Negotiation in HTTP"
Koen Holtman, TUE Koen Holtman, TUE
Andrew Mutz, Hewlett Packard Andrew Mutz, Hewlett Packard
March 1998. March 1998.
(Non-normative)
[6] RFC 2530, "Indicating Supported Media Features Using Extensions [6] RFC 2530, "Indicating Supported Media Features Using Extensions
to DSN and MDN" to DSN and MDN"
Dan Wing, Cisco Systems Dan Wing, Cisco Systems
March 1999. March 1999.
(Non-normative)
[7] RFC 2045, "Multipurpose Internet Mail Extensions (MIME) [7] RFC 2045, "Multipurpose Internet Mail Extensions (MIME)
Part 1: Format of Internet message bodies" Part 1: Format of Internet message bodies"
N. Freed, Innosoft N. Freed, Innosoft
N. Borenstein, First Virtual N. Borenstein, First Virtual
November 1996. November 1996.
[8] RFC 2046, "Multipurpose Internet Mail Extensions (MIME) [8] RFC 2046, "Multipurpose Internet Mail Extensions (MIME)
Part 2: Media types" Part 2: Media types"
N. Freed, Innosoft N. Freed, Innosoft
N. Borenstein, First Virtual N. Borenstein, First Virtual
November 1996. November 1996.
[9] RFC 2434, "Guidelines for Writing an IANA Considerations Section [9] RFC 2434, "Guidelines for Writing an IANA Considerations Section
in RFCs" in RFCs"
T. Narten, IBM T. Narten, IBM
H. Alvestrand, Maxware H. Alvestrand, Maxware
October 1998. October 1998.
Internet draft MIME content types in media feature expressions
[10] "Registration of Charset and Languages Media Features Tags" [10] "Registration of Charset and Languages Media Features Tags"
Paul Hoffman, IMC Paul Hoffman, IMC
Internet draft: <draft-hoffman-char-lang-media-01.txt> Internet draft: <draft-hoffman-char-lang-media-01.txt>
Work in progress, July 1999. Work in progress, July 1999.
(Non-normative)
Internet draft MIME content types in media feature expressions
30 November 1999
9. Author's address 9. Author's address
Graham Klyne Graham Klyne
Content Technologies Ltd. Content Technologies Ltd.
1220 Parkview, 1220 Parkview,
Arlington Business Park Arlington Business Park
Theale Theale
Reading, RG7 4SA Reading, RG7 4SA
United Kingdom. United Kingdom.
Telephone: +44 118 930 1300 Telephone: +44 118 930 1300
Facsimile: +44 118 930 1301 Facsimile: +44 118 930 1301
E-mail: GK@ACM.ORG E-mail: GK@ACM.ORG
Appendix A: 'Type' feature tag registration Appendix A: 'Type' feature tag registration
- Media Feature tag name(s): - Media Feature tag name(s):
Type Type
- ASN.1 identifiers associated with this feature tag: - ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]] [[[New assignment by IANA]]]
- Summary of the media features indicated: - Summary of the media features indicated:
This feature tag indicates a MIME content type that a message This feature tag indicates a MIME content type that a message
agent is capable of handling, or contained within some message agent is capable of handling, or that is contained within some
data. message data.
The content type consists of the MIME media type and subtype, The content type consists of the MIME media type and subtype,
presented using all lower case letters and with any whitespace presented using all lower case letters and with any whitespace
characters removed. characters removed.
In exceptional cases, content type parameters may be included, in
which case the parameter name is also presented in lower case
letters, with all whitespace surrounding the ';' and '=' removed.
The parameter value should be presented in some canonical form.
- Values appropriate for use with this feature tag: - Values appropriate for use with this feature tag:
String String
- The feature tag is intended primarily for use in the following - The feature tag is intended primarily for use in the following
applications, protocols, services, or negotiation mechanisms: applications, protocols, services, or negotiation mechanisms:
Any application that wishes to convey MIME content type Any application that wishes to convey MIME content type
information in a media feature expression. information in a media feature expression.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
- Examples of typical use: - Examples of typical use:
(type="text/plain") (type="image/tiff")
(type="text/plain;charset=iso-8859-1")
The second example is not a recommended form; the preferred form (& (type="text/plain") (charset=US-ASCII) )
is to use a 'charset' feature tag, per [10]. But note that all
spaces around the 'charset' parameter are removed, and the name
and value are presented in lower case.
- Related standards or documents: - Related standards or documents:
MIME, RFC 2045 [7] MIME, RFC 2045 [7]
MIME, RFC 2046 [8] MIME, RFC 2046 [8]
Registration of Charset and Languages Media Features Tags [10] Registration of Charset and Languages Media Features Tags [10]
- Considerations particular to use in individual applications, - Considerations particular to use in individual applications,
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String feature matching is case sensitive, so consistent use of String feature matching is case sensitive, so consistent use of
case for content type values and parameters is essential if case for content type values and parameters is essential if
content type value matching is to be achieved in a fashion content type value matching is to be achieved in a fashion
consistent with MIME content type matching. consistent with MIME content type matching.
Similarly, white space must be used consistently. Similarly, white space must be used consistently.
This registration specifies a canonical form to be used for This registration specifies a canonical form to be used for
content type values (lower case letters and remove all content type values (lower case letters and remove all
whitespace). If content type parameters are introduced, all whitespace).
letters and whitespace that are not part of the parameter value
are treated similarly. The canonical form for parameter values
must be appropriate to the equivalence rules for that value.
- Related feature tags: - Related feature tags:
(N/A) (N/A)
- Intended usage: - Intended usage:
Common Common
- Author/Change controller: - Author/Change controller:
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(N/A) (N/A)
- Intended usage: - Intended usage:
Common Common
- Author/Change controller: - Author/Change controller:
IETF IETF
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
Full copyright statement Full copyright statement
Copyright (C) The Internet Society 1999. All Rights Reserved. Copyright (C) The Internet Society 2000. All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied, it or assist in its implementation may be prepared, copied,
published and distributed, in whole or in part, without restriction published and distributed, in whole or in part, without restriction
of any kind, provided that the above copyright notice and this of any kind, provided that the above copyright notice and this
paragraph are included on all such copies and derivative works. paragraph are included on all such copies and derivative works.
However, this document itself may not be modified in any way, such However, this document itself may not be modified in any way, such
as by removing the copyright notice or references to the Internet as by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the Society or other Internet organizations, except as needed for the
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revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Internet draft MIME content types in media feature expressions Internet draft MIME content types in media feature expressions
30 November 1999
Revision history Revision history
[[[RFC editor: please reove this section on publication]]] [[[RFC editor: please reove this section on publication]]]
00a 16-Feb-1999 Initial draft. 00a 16-Feb-1999 Initial draft.
01a 16-Feb-1999 Added pointers to mailing list for discussion. 01a 16-Feb-1999 Added pointers to mailing list for discussion.
01b 04-Mar-1999 Various editorial improvements. 01b 04-Mar-1999 Various editorial improvements.
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parameter issue in the introduction. parameter issue in the introduction.
02b 20-Jul-1999 Incorporate review comments. Also cite charset 02b 20-Jul-1999 Incorporate review comments. Also cite charset
feature type registration work-in-progress. feature type registration work-in-progress.
02c 14-Nov-1999 Fix RFC 2533 number in references. 02c 14-Nov-1999 Fix RFC 2533 number in references.
02d 30-Nov-1999 Add note about 'charset' feature tag to 02d 30-Nov-1999 Add note about 'charset' feature tag to
registration template. Moved copyright notice to registration template. Moved copyright notice to
end of document text. end of document text.
03a 04-Apr-2000 Restrict type tag value to content-type, without
parameters. Add text explaining how to deal with
content-type parameters in media feature
expressions.
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