draft-ietf-conneg-content-features-01.txt   draft-ietf-conneg-content-features-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
Indicating media features for MIME content Indicating media features for MIME content
<draft-ietf-conneg-content-features-01.txt> <draft-ietf-conneg-content-features-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
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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 "A syntax for describing media feature sets", an expression
format is presented for describing media feature capabilities using format is presented for describing media feature capabilities using
simple media feature tags. simple media feature tags.
This memo defines a MIME 'Content-features:' header that can be This memo defines a MIME 'Content-features:' header that can be
used to annotate a MIME message part using this expression format, used to annotate a MIME message part using this expression format,
and indicates some ways it might be used. and indicates some ways it might be used.
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
Table of contents Table of contents
1. Introduction ............................................2 1. Introduction ............................................2
1.1 Terminology and document conventions 3 1.1 Terminology and document conventions 3
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. The 'Content-features:' MIME header .....................4 3. The 'Content-features:' MIME header .....................4
3.1 Usage considerations 4 3.1 Usage considerations 4
3.1.1 Simple message parts 4 3.1.1 Simple message parts 4
3.1.2 Multipart and other composites 5 3.1.2 Multipart and other composites 5
3.1.3 Reference to external data 5 3.1.3 Reference to external data 5
4. Examples ................................................5 4. Examples ................................................5
4.1 Simple message 5 4.1 Simple message 5
4.2 Fax message 6 4.2 Fax message 6
4.3 Multipart/alternative data 7 4.3 Multipart/alternative data 6
4.4 Reference to external message data 7 4.4 Reference to external message data 7
4.5 Compressed data 8 4.5 Compressed data 8
4.6 Multipart/related data 8 4.6 Multipart/related data 8
5. Security considerations .................................9 5. Security considerations .................................9
6. Full copyright statement ................................9 6. Acknowledgements ........................................9
7. Acknowledgements ........................................10 7. References ..............................................9
8. References ..............................................10 8. Author's address ........................................10
9. Author's address ........................................11 Full copyright statement ...................................11
Appendix A: Revision history ...............................11 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.
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expressions. This header provides a means to indicate media- expressions. This header provides a means to indicate media-
related features of message content that go beyond the MIME content related features of message content that go beyond the MIME content
type. type.
Along with the new MIME header definition, consideration is also Along with the new MIME header definition, consideration is also
given to how it may be used to present message media content given to how it may be used to present message media content
information that is problematic to express within the basic MIME information that is problematic to express within the basic MIME
framework. framework.
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
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
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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 Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
2. Motivation and goals 2. Motivation and goals
It is envisaged that media feature labelling of message parts may It is envisaged that media feature labelling of message parts may
be used in the following ways: be used in the following ways:
o to supply more detailed media feature information about a message o to supply more detailed media feature information about a message
content than can be provided by the 'Content-type:' header. content than can be provided by the 'Content-type:' header.
o to provide summary media feature information (possibly including o to provide summary media feature information (possibly including
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3.1 Usage considerations 3.1 Usage considerations
3.1.1 Simple message parts 3.1.1 Simple message parts
When applied to a simple MIME message part, the header should When applied to a simple MIME message part, the header should
appear just once and is used to convey additional information about appear just once and is used to convey additional information about
the message part content that goes beyond that provided by the MIME the message part content that goes beyond that provided by the MIME
'Content-type:' header field. The 'Content-features:' header may 'Content-type:' header field. The 'Content-features:' header may
indicate a content type that is different than that given by the indicate a content type that is different than that given by the
MIME 'Content-type:' header. This is possible but not recommended: MIME 'Content-type:' header. This is possible but not recommended
In such cases, MIME content type processing must be performed in when applied to a non-composite body part: in any case, MIME
accordance with the MIME 'Content-type:' header.
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
content type processing must be performed in accordance with the
'Content-type:' header.
NOTE: Once the message content has been delivered to an NOTE: Once the message content has been delivered to an
application, it is possible that subsequent processing application, it is possible that subsequent processing
may be affected by content type information indicated by may be affected by content type information indicated by
the media feature expression. the media feature expression.
3.1.2 Multipart and other composites 3.1.2 Multipart and other composites
'Content-features:' headers may be applied to a MIME multipart 'Content-features:' headers may be applied to a MIME multipart
indicating information about the inner content of the multipart. indicating information about the inner content of the multipart.
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For example, media information --including contained MIME content For example, media information --including contained MIME content
type(s)-- about the data referenced by a MIME 'Message/external- type(s)-- about the data referenced by a MIME 'Message/external-
body' may be conveyed. body' may be conveyed.
4. Examples 4. Examples
4.1 Simple message 4.1 Simple message
Mime-Version: 1.0 Mime-Version: 1.0
Content-type: text/plain Content-type: text/plain;charset=US-ASCII
Content-features: (& (paper-size=A4) (ua-media=stationery) ) Content-features: (& (paper-size=A4) (ua-media=stationery) )
: :
(data) (data)
: :
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
4.2 Fax message 4.2 Fax message
Mime-Version: 1.0 Mime-Version: 1.0
Content-Type: multipart/fax-message; boundary="break" Content-Type: multipart/mixed; boundary="break"
Content-features: Content-features:
(& (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) (dpi-xyratio=200/100)
(paper-size=A4) (paper-size=A4)
(image-coding=MH) (MRC-mode=0) (image-coding=MH) (MRC-mode=0)
(ua-media=stationery) ) (ua-media=stationery) )
--break --break
Content-Type: image/tiff; name="coverpage.tiff" Content-Type: image/tiff; name="coverpage.tiff"
Content-Coverpage: yes
Content-Transfer-Encoding: base64 Content-Transfer-Encoding: base64
Content-Description: This part is a coverpage Content-Description: This part is a coverpage
Content-Disposition: attachment; filename="coverpage.tiff" Content-Disposition: attachment; filename="coverpage.tiff"
0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAAAAAA 0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAAAAAA
AAAAAAAAEAAAZAAAAAEAAAD+////AAAAAAAAAAD//////////////////// AAAAAAAAEAAAZAAAAAEAAAD+////AAAAAAAAAAD////////////////////
: :
(more data) (more data)
: :
--break --break
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Content-Transfer-Encoding: base64 Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="document.tiff" Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
: :
(more data) (more data)
: :
--break-- --break--
Internet draft Indicating media features for MIME content
13 April 1999
4.3 Multipart/alternative data 4.3 Multipart/alternative data
This example illustrates two points:
o Information about the various parts in a multipart/alternative
can be made available before the alternative body parts are
processed. This may facilitiate optimum one-pass processing of
multipart/alternative data.
o There may be alternatives having the same basic MIME content-
type, but differing in the content features that they use.
Internet draft Indicating media features for MIME content
30 November 1999
Mime-Version: 1.0 Mime-Version: 1.0
Content-Type: multipart/alternative; bounday="break" Content-Type: multipart/alternative; boundary="break"
Content-features: (Type="text/plain") Content-features: (& (Type="text/plain") (charset=US-ASCII) )
Content-features: (& (Type="text/html") (color=binary) ) Content-features:
Content-features: (& (Type="text/html") (color=limited) ) (& (Type="text/html") (charset=ISO-8859-1) (color=binary) )
Content-features:
(& (Type="text/html") (charset=ISO-8859-1) (color=limited) )
--break --break
Content-type: (Type="text/plain") Content-type: "text/plain";charset="US-ASCII"
: :
(data) (data)
: :
--break --break
Content-type: text/html Content-type: text/html;charset="iso-8859-1"
Content-features: (color=binary) Content-features: (color=binary)
: :
(data) (data)
: :
--break --break
Content-type: text/html Content-type: text/html;charset="iso-8859-1"
Content-features: (color=limited) Content-features: (color=limited)
: :
(data) (data)
: :
--break-- --break--
4.4 Reference to external message data 4.4 Reference to external message data
Mime-Version: 1.0 Mime-Version: 1.0
Content-type: message/external-body; access-type=URL; Content-type: message/external-body; access-type=URL;
URL="http://www.foo.com/file1.html" URL="http://www.foo.com/file1.html"
Content-type: Multipart/mixed Content-type: Multipart/mixed
Content-features: (Type="text/plain") Content-features: (& (Type="text/plain") (charset=US-ASCII) )
Content-features: (& (Type="image/tiff") (color=limited) ) Content-features: (& (Type="image/tiff") (color=limited) )
<end> <end>
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
4.5 Compressed data 4.5 Compressed data
This example shows how the "Content-features" header can be used to This example shows how the "Content-features" header can be used to
overcome the problem noted in the MIME registration for overcome the problem noted in the MIME registration for
"Application/zip" regarding information about the data content. "Application/zip" regarding information about the data content.
Mime-Version: 1.0 Mime-Version: 1.0
Content-type: application/zip Content-type: application/zip
Content-features: (Type="text/plain") Content-features: (& (Type="text/plain") (charset=US-ASCII) )
Content-features: (& (Type="image/tiff") (color=limited) ) Content-features: (& (Type="image/tiff") (color=limited) )
Content-transfer-encoding: base64 Content-transfer-encoding: base64
: :
(data) (data)
: :
<end> <end>
4.6 Multipart/related data 4.6 Multipart/related data
(See also: RFC 2387, "The MIME Multipart/Related Content-type" [8])
Mime-Version: 1.0 Mime-Version: 1.0
Content-Type: multipart/related; boundary="boundary-example"; Content-Type: multipart/related; boundary="boundary-example";
type="text/html"; start="<foo3@foo1@bar.net>" type="text/html"; start="<foo3@foo1@bar.net>"
Content-features: (type="text/html") Content-features: (& (type="text/html") (charset=US-ASCII) )
Content-features: (type="image/gif") Content-features: (type="image/gif")
--boundary-example --boundary-example
Content-Type: text/html;charset="US-ASCII" Content-Type: text/html;charset="US-ASCII"
Content-ID: <foo3@foo1@bar.net> Content-ID: <foo3@foo1@bar.net>
... text of the HTML document, which might contain a URI ... text of the HTML document, which might contain a URI
referencing a resource in another body part, for example referencing a resource in another body part, for example
through a statement such as: through a statement such as:
<IMG SRC="http://www.ietf.cnri.reston.va.us/images/ietflogo.gif" <IMG SRC="http://www.ietf.cnri.reston.va.us/images/ietflogo.gif"
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Content-Type: IMAGE/GIF Content-Type: IMAGE/GIF
Content-Transfer-Encoding: BASE64 Content-Transfer-Encoding: BASE64
R0lGODlhGAGgAPEAAP/////ZRaCgoAAAACH+PUNvcHlyaWdodCAoQykgMTk5 R0lGODlhGAGgAPEAAP/////ZRaCgoAAAACH+PUNvcHlyaWdodCAoQykgMTk5
NSBJRVRGLiBVbmF1dGhvcml6ZWQgZHVwbGljYXRpb24gcHJvaGliaXRlZC4A NSBJRVRGLiBVbmF1dGhvcml6ZWQgZHVwbGljYXRpb24gcHJvaGliaXRlZC4A
etc... etc...
--boundary-example-- --boundary-example--
Internet draft Indicating media features for MIME content Internet draft Indicating media features for MIME content
13 April 1999 30 November 1999
5. Security considerations 5. Security considerations
When applied to simple or multipart MIME formatted data, a media When applied to simple or multipart MIME formatted data, a media
feature expression provides summary information about the message feature expression provides summary information about the message
data, which in many cases can be determined by examination of the data, which in many cases can be determined by examination of the
message content. Under these circumstances, no additional security message content. Under these circumstances, no additional security
considerations appear to be raised. considerations appear to be raised.
When applied to other message composites, especially encrypted When applied to other message composites, especially encrypted
message content, feature expressions may disclose information that message content, feature expressions may disclose information that
is otherwise unavailable. In these cases, some security is otherwise unavailable. In these cases, some security
considerations associated with media content negotiation [1,2] may considerations associated with media content negotiation [1,2] may
have greater relevance. have greater relevance.
It is suggested here that media feature descriptions may be It is suggested here that media feature descriptions may be
usefully employed with encrypted message content. In doing this, usefully employed with encrypted message content. In doing this,
take care to ensure that the purpose of encryption is not take care to ensure that the purpose of encryption is not
compromised. compromised (e.g. encryption might be intended to conceal the fact
that a particular application data format is being used, which fact
6. Full copyright statement might be disclosed by an injudiciously applied Content-features
header).
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 Indicating media features for MIME content
13 April 1999
7. Acknowledgements 6. Acknowledgements
This proposal draws from discussions with Dan Wing. The fax This proposal draws from discussions with Dan Wing. The fax
message example was taken from a proposal by Mike Ruhl. The message example was taken from a proposal by Mike Ruhl. The
multipart/related example is developed from RFC 2557. multipart/related example is developed from RFC 2557.
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: Mr Hiroshi Tamura, comments that led to significant improvements: Mr Hiroshi Tamura,
Ted Hardie. Ted Hardie, Maurizio Codogno, Jacob Palme.
8. References 7. 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.
[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.
[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.
Internet draft Indicating media features for MIME content
30 November 1999
[4] RFC 822, "Standard for the format of ARPA Internet text messages" [4] RFC 822, "Standard for the format of ARPA Internet text messages"
D. Crocker, Department of Electrical Engineering, University of D. Crocker, Department of Electrical Engineering, University of
Delaware Delaware
August 1982. August 1982.
To be replaced by: To be replaced by:
"Internet Message Format Standard" "Internet Message Format Standard"
P. Resnick (editor), QUALCOMM Incorporated P. Resnick (editor), QUALCOMM Incorporated
Internet draft: <draft-ietf-drums-msg-fmt-07.txt> Internet draft: <draft-ietf-drums-msg-fmt-07.txt>
Work in progress, January 1999. Work in progress, January 1999.
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N. Freed, Innosoft N. Freed, Innosoft
N. Borenstein, First Virtual N. Borenstein, First Virtual
November 1996. November 1996.
[6] RFC 2046, "Multipurpose Internet Mail Extensions (MIME) [6] 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.
Internet draft Indicating media features for MIME content
13 April 1999
[7] RFC 2017, "Definition of the URL MIME External-Body Access-Type" [7] RFC 2017, "Definition of the URL MIME External-Body Access-Type"
N. Freed, Innosoft N. Freed, Innosoft
K. Moore, University of Tennessee K. Moore, University of Tennessee
A. Cargille, WG Chair A. Cargille, WG Chair
October 1996 October 1996
9. Author's address [8] RFC 2387, "The MIME Multipart/Related Content-type"
E. Levinson
August 1998
[9] "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.
8. 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
Appendix A: Revision history Internet draft Indicating media features for MIME content
30 November 1999
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.
Revision history
[[[RFC editor: please remove this section on publication]]] [[[RFC editor: please remove this section on publication]]]
00a 10-Feb-1999 Initial draft. 00a 10-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 changes. Added placeholder for 01b 04-Mar-1999 Various editorial changes. Added placeholder for
multipart/related example. multipart/related example.
01c 13-Apr-1999 Separated multipart/alternative and 01c 13-Apr-1999 Separated multipart/alternative and
message/external-body into separate examples. message/external-body into separate examples.
Added example for compressed data. Added example Added example for compressed data. Added example
for multipart/related data. Updated references. for multipart/related data. Updated references.
02a 20-Jul-1999 Incorporated review comments -- editorial changes.
02b 29-Nov-1999 Added (charset=...) to (type=text/*) examples.
Added citation to charset and language feature
registration document.
Internet draft Indicating media features for MIME content
30 November 1999
02c 29-Nov-1999 Indicated motivation for multipart/alternative
example. Moved copyright section to end of text.
 End of changes. 37 change blocks. 
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