draft-ietf-conneg-feature-type-01.txt   draft-ietf-conneg-feature-type-02.txt 
IETF conneg working group Graham Klyne IETF conneg working group Graham Klyne
Internet draft 5GM/Content Technologies Internet draft Content Technologies
Expires: October 1999 Category: Work-in-progress 30 November 1999
MIME content types in media feature expressions MIME content types in media feature expressions
<draft-ietf-conneg-feature-type-01.txt> <draft-ietf-conneg-feature-type-02.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.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 37 skipping to change at page 1, line 36
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society 1999. All Rights Reserved. Copyright (C) The Internet Society 1999. All Rights Reserved.
Abstract Abstract
In "A syntax for describing media feature sets", an expression In RFC 2533, "A syntax for describing media feature sets", an
format is presented for describing media feature capabilities using expression format is presented for describing media feature
simple media feature tags. capabilities using 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 ....................................3 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
4.3 Voice message 5 4.3 Voice message 5
4.4 Web browser capabilities 5 4.4 Web browser capabilities 6
5. IANA considerations .....................................6 5. IANA considerations .....................................6
6. Security considerations .................................6 6. Security considerations .................................6
7. Full copyright statement ................................6 7. Acknowledgements ........................................6
8. Acknowledgements ........................................6 8. References ..............................................6
9. References ..............................................7 9. Author's address ........................................8
10. Author's address .......................................8 Appendix A: 'Type' feature tag registration ................8
Appendix A: 'Type' feature tag registration ................9 Full copyright statement ...................................10
Appendix B: Revision history ...............................10 Revision history ...........................................11
1. Introduction 1. Introduction
In "A syntax for describing media feature sets" [1], an expression In "A syntax for describing media feature sets" [1], an expression
format is presented for describing media feature capabilities as a format is presented for describing media feature capabilities as a
combination of simple media feature tags, registered according to combination of simple media feature tags, registered according to
"Media Feature Tag Registration Procedure" [2]. This provides a "Media Feature Tag Registration Procedure" [2]. This provides a
format for message handling agents to describe the media feature format for message handling agents to describe the media feature
content of messages that they can handle. content of messages that they can handle.
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.
Note that a content type feature value may contain parameters, but
this is discouraged. See section 3 and appendix A "Summary of the
media features indicated" for discussion of this point.
1.1 Terminology and document conventions 1.1 Terminology and document conventions
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
skipping to change at page 4, line 6 skipping to change at page 4, line 6
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
be apply to content type information unless it appears in the apply to content type information unless it appears in the
feature expression. feature expression.
For example, in HTTP 1.1 [4] with Transparent Content Negotiation For example, in HTTP 1.1 [4] with Transparent Content Negotiation
(TCN) [5] acceptable content types and other media features are (TCN) [5] acceptable content types and other media features are
indicated in different request headers, with no clear way to indicated in different request headers, with no clear way to
indicate that they may be acceptable only in certain indicate that they may be acceptable only in certain
combinations. combinations.
o It is sometimes useful for all media capability information to be o It is sometimes useful for all media capability information to be
included in a single expression. For example, DSN and MDN included in a single expression. For example, DSN and MDN
skipping to change at page 5, line 6 skipping to change at page 5, line 6
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 in the corresponding MIME-
formatted data). formatted data).
The media type should be given without any parameter values. The The media type should be given without any parameter values. The
intention here is that information that is conveyed in MIME content intention here is that information that is conveyed in MIME content
type parameters is more usefully handled in a media feature type parameters is more usefully handled in a media feature
expression by separate feature tags. 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
NOTE: content type parameters in a 'type' value are NOTE: content type parameters in a 'type' value are
strongly discouraged, but not prohibited. In deciding strongly discouraged, but not prohibited. In deciding
whether or not to include a parameter value, implementers whether or not to include a parameter value, implementers
should bear in mind the feature set matching rules [1]. should bear in mind the feature set matching rules [1].
These would cause 'type' values with and without These would cause 'type' values with and without
parameters to be treated as completely distinct values, parameters to be treated as completely distinct values,
which may lead to unexpected results. which may lead to unexpected results.
4. Examples 4. Examples
4.1 Simple text 4.1 Simple text
(& (type="text/plain") (color=binary) (paper-size=A4) ) (& (type="text/plain") (charset=US-ASCII)
(color=binary) (paper-size=A4) )
4.2 Fax image 4.2 Fax image
(& (type="image/tiff") (& (type="image/tiff")
(color=binary) (color=binary)
(image-file-structure=TIFF-S) (image-file-structure=TIFF-S)
(dpi=200) (dpi=200)
(dpi-xyratio=[200/100,200/200]) (dpi-xyratio=[200/100,200/200])
(paper-size=A4) (paper-size=A4)
(image-coding=MH) (MRC-mode=0) (image-coding=MH) (MRC-mode=0)
skipping to change at page 6, line 6 skipping to change at page 6, line 6
(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") (color=limited)) (| (& (type="text/html") (charset=iso-8859-1) (color=limited))
(type="text/plain") (& (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
Appendix A of this document calls for registrations of feature tags Appendix A of this document calls for registration of a feature tag
in the "IETF tree", as defined in section 3.1.1 of "Media Feature in the "IETF tree", as defined in section 3.1.1 of "Media Feature
Tag Registration Procedure" [2] (i.e. these feature tags are Tag Registration Procedure" [2] (i.e. these feature tags are
subject to the "IETF Consensus" policies described in RFC 2434 subject to the "IETF Consensus" policies described in RFC 2434
[9]). [9]).
ASN.1 identifiers should be assigned for each of these registered An ASN.1 identifier should be assigned for this registered feature
feature tags and replaced in the body of the registration. tag and replaced in the body of the registration.
6. Security considerations 6. Security considerations
This memo is not believed to introduce any security considerations This memo is not believed to introduce any security considerations
that are not already inherent in the use of media feature tags and that are not already inherent in the use of media feature tags and
expressions [1,2]. expressions [1,2].
7. Full copyright statement 7. Acknowledgements
Copyright (C) The Internet Society 1999. 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.
Internet draft MIME content types in media feature expressions
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.
8. 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. Masinter, Paul Hoffman, Jacob Palme.
9. References 8. References
[1] RFC 2253, "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.
[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.
[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.
Internet draft MIME content types in media feature expressions
[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.
[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.
skipping to change at page 8, line 30 skipping to change at page 7, line 49
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.
10. Author's address [10] "Registration of Charset and Languages Media Features Tags"
Paul Hoffman, IMC
Internet draft: <draft-hoffman-char-lang-media-01.txt>
Work in progress, July 1999.
Internet draft MIME content types in media feature expressions
30 November 1999
9. Author's address
Graham Klyne Graham Klyne
5th Generation Messaging Ltd. Content Technologies Ltd. Content Technologies Ltd.
5 Watlington Street Forum 1, Station Road 1220 Parkview,
Nettlebed Theale Arlington Business Park
Henley-on-Thames, RG9 5AB Reading, RG7 4RA Theale
United Kingdom United Kingdom. Reading, RG7 4SA
Telephone: +44 1491 641 641 +44 118 930 1300 United Kingdom.
Facsimile: +44 1491 641 611 +44 118 930 1301 Telephone: +44 118 930 1300
Facsimile: +44 118 930 1301
E-mail: GK@ACM.ORG E-mail: GK@ACM.ORG
Internet draft MIME content types in media feature expressions
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 identifiers associated with this feature tag:
[[[New assignments by IANA]]] [[[New assignments by IANA]]]
skipping to change at page 9, line 42 skipping to change at page 9, line 5
- 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
30 November 1999
- Examples of typical use: - Examples of typical use:
(type="text/plain") (type="text/plain")
(type="text/plain;charset=iso-8859-1") (type="text/plain;charset=iso-8859-1")
The second example is not a recommended form. But note that all The second example is not a recommended form; the preferred form
is to use a 'charset' feature tag, per [10]. But note that all
spaces around the 'charset' parameter are removed, and the name spaces around the 'charset' parameter are removed, and the name
and value are presented in lower case. 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]
Internet draft MIME content types in media feature expressions Registration of Charset and Languages Media Features Tags [10]
- Considerations particular to use in individual applications, - Considerations particular to use in individual applications,
protocols, services, or negotiation mechanisms: protocols, services, or negotiation mechanisms:
(N/A) (N/A)
- Interoperability considerations: - Interoperability considerations:
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
skipping to change at page 11, line 6 skipping to change at page 10, line 6
- 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
Appendix B: Revision history Full copyright statement
Copyright (C) The Internet Society 1999. 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.
Internet draft MIME content types in media feature expressions
30 November 1999
Revision history
[[[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.
01c 29-Apr-1999 Improved web browser example. 01c 29-Apr-1999 Improved web browser example.
TODO: 02a 29-Apr-1999 Highlight and forward reference the content-type
parameter issue in the introduction.
o Discuss: should the feature syntax be extended to allow content 02b 20-Jul-1999 Incorporate review comments. Also cite charset
types to be "unstringed", hence providing more relaxed matching feature type registration work-in-progress.
rules?
02c 14-Nov-1999 Fix RFC 2533 number in references.
02d 30-Nov-1999 Add note about 'charset' feature tag to
registration template. Moved copyright notice to
end of document text.
 End of changes. 33 change blocks. 
71 lines changed or deleted 101 lines changed or added

This html diff was produced by rfcdiff 1.34. The latest version is available from http://tools.ietf.org/tools/rfcdiff/