As per Relevance of the word registration, we have this rfc below:
Network Working Group G.
Request for Comments: 2913 Content
Category: Standards Track September 2000
MIME Content Types in Media Feature
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
In "A Syntax for Describing Media Feature Sets", an expression
is presented for describing media feature capabilities using
media feature tags
This memo defines a media feature tag whose value is a
Internet Mail Extensions (MIME) content type. This allows
construction of feature expressions that take account of the
content type of the corresponding data
Table of
1. Introduction .................................................. 2
1.1 Terminology and document conventions ...................... 2
2. Motivation and goals .......................................... 3
3. MIME content type feature tag ................................. 3
4. Examples ...................................................... 4
4.1 Simple text ............................................... 4
4.2 Fax image ................................................. 4
4.3 Voice message ............................................. 4
4.4 Web browser capabilities .................................. 5
5. IANA Considerations ........................................... 5
6. Security Considerations ....................................... 5
7. Acknowledgements .............................................. 5
8. References .................................................... 6
9. Author's Address .............................................. 6
Appendix A: 'Type' feature tag registration ...................... 7
Full Copyright Statement ......................................... 9
Klyne Standards Track [Page 1]
RFC 2913 MIME Content in Media Feature Expressions September 2000
1.
In "A Syntax for Describing Media Feature Sets" [1], an
format is presented for describing media feature capabilities as
combination of simple media feature tags, registered according
"Media Feature Tag Registration Procedure" [2]. This provides
format for message handling agents to describe the media
content of messages that they can handle
This memo defines a media feature tag whose value is a MIME
type. This allows the construction of feature expressions that
account of the MIME content type of the corresponding data
Note that a content type feature value may contain parameters,
this is discouraged. See section 3 and appendix A, "Summary of
media features indicated" for discussion of this point
1.1 Terminology and document
This section defines a number of terms and other
conventions, which are used with specific meaning in this memo
media
information that indicates facilities assumed to be
for the message content to be properly rendered or
presented. Media features are not intended to
information that affects message transmission
feature
some set of media features described by a media
assertion, as described in "A Syntax for Describing
Feature Sets" [1]. (See that memo for a more formal
of this term.)
feature set
a string that describes some feature set, formulated
to the rules in "A Syntax for Describing Media Feature Sets
[1] (and possibly extended by other specifications).
This specification uses syntax notation and conventions described
RFC 2234, "Augmented BNF for Syntax Specifications: ABNF" [3].
NOTE: Comments like this provide additional
information about the rationale behind this document.
information is not needed for building a
implementation, but may help those who wish to understand
design in greater depth
Klyne Standards Track [Page 2]
RFC 2913 MIME Content in Media Feature Expressions September 2000
2. Motivation and
The media feature expression syntax [1] and feature tags [2]
designed with a view to providing content media information
augments basic MIME content type information. There are
situations where it is useful to be able include that content
information in a media feature expression
o Media feature details may depend upon the content type being used
The media feature combining algebra and syntax [1] cannot apply
content type information unless it appears in the
expression
For example, in HTTP 1.1 [4] with Transparent Content
(TCN) [5] acceptable content types and other media features
indicated in different request headers, with no clear way
indicate that they may be acceptable only in certain combinations
o It is sometimes useful for all media capability information to
included in a single expression. For example, DSN and
extensions [6] that allow a recipient to indicate
capabilities provide a single field for conveying
information
o When media features are used to describe a message content,
may refer to inner parts of a MIME composite; e.g. the
parts of a 'multipart', files in a compressed archive,
encrypted message data
3. MIME content type feature
Feature tag name Legal
---------------- ------------
type
containing a MIME content-type value
Reference: this document, appendix A
The 'type' feature tag indicates a MIME media content type (i.e
that appears in a 'Content-type:' header of the corresponding MIME
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 content type must be given without any content-type
values
Klyne Standards Track [Page 3]
RFC 2913 MIME Content in Media Feature Expressions September 2000
To include information in media feature expressions that is
conveyed in a MIME content-type parameter, a separate media
tag should be registered [2] and used in the media
expression. This is illustrated by the use of 'charset' in
example at 4.1 below -- the 'charset' tag is defined by a
registration [10].
NOTE: Allowing content-type parameters to be part of a type
value was considered, but rejected because of concerns
canonicalization, ordering, case sensitivity, etc. Only exact
case-sensitive, character matching is defined for media
expressions [1].
4.
4.1 Simple
(& (type="text/plain") (charset=US-ASCII
(color=binary) (paper-size=A4) )
4.2 Fax
(& (type="image/tiff")
(color=binary
(image-file-structure=TIFF-S
(dpi=200)
(dpi-xyratio=[200/100,200/200])
(paper-size=A4)
(image-coding=MH) (MRC-mode=0)
(ua-media=stationery) )
4.3 Voice
(& (type="multipart/voice-message")
(VPIM-version="3.0")
(audio-codec=[G726-32,GSM-610])
(audio-file-structure=[None,WAV])
(ua-terminal=mobile-handset
(audio-channels=1) )
NOTE: in this case, some media features apply to MIME
contained within the declared 'multipart/voice- message
content type. The goal here is not so much to mirror the
structure as to convey useful information about the (possible
message content
Klyne Standards Track [Page 4]
RFC 2913 MIME Content in Media Feature Expressions September 2000
4.4 Web browser
(& (pix-x<=800) (pix-y<=600)
(| (& (type="text/html") (charset=iso-8859-1)
(color=limited) )
(& (type="text/plain") (charset=US-ASCII) )
(& (type="image/gif") (color=mapped))
(& (type="image/jpeg") (color=full) ) ) )
This example describes an HTML viewer that can deal with a
number of color text tags, a gif viewer that supports mapped color
and a jpeg viewer that supports color
5. IANA
Appendix A of this document calls for registration of a feature
in the "IETF tree", as defined in section 3.1.1 of "Media Feature
Registration Procedure" [2] (i.e. these feature tags are subject
the "IETF Consensus" policies described in RFC 2434 [9]).
ASN.1 identifier 1.3.6.1.8.1.30 has been assigned by the IANA
this registered feature tag and has been placed in the body of
registration
6. Security
This memo is not believed to introduce any security
that are not already inherent in the use of media feature tags
expressions [1,2].
7.
This proposal draws from discussions in the IETF 'conneg'
group. The voice message example is based on some ideas by
Parsons
The author would like to thank the following people who
comments that led to significant improvements: Ted Hardie,
Masinter, Paul Hoffman, Jacob Palme, Ned Freed
Klyne Standards Track [Page 5]
RFC 2913 MIME Content in Media Feature Expressions September 2000
8.
[1] Klyne, G., "A Syntax for Describing Media Feature Sets",
2533, March 1999.
[2] Holtman, K., Mutz, A. and T. Hardie, "Media Feature
Registration Procedure", RFC 2506, March 1999.
[3] Crocker, D. and P. Overell, "Augmented BNF for
Specifications: ABNF", RFC 2234, November 1997.
[4] Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2068, January 1997.
[5] Holtman, K. and A. Mutz, "Transparent Content Negotiation
HTTP", RFC 2295, March 1998.
[6] Wing, D., "Indicating Supported Media Features Using
to DSN and MDN", RFC 2530, March 1999.
[7] Freed, N. and N. Borenstein, "Multipurpose Internet
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
[8] Freed, N. and N. Borenstein, "Multipurpose Internet
Extensions (MIME) Part Two: Media Types", RFC 2046,
1996.
[9] Narten, T. and H. Alvestrand, "Guidelines for Writing an
Considerations Section in RFCs", RFC 2434, October 1998.
[10] Hoffman, P., "Registration of Charset and Languages
Features Tags", Work in Progress
9. Author's
Graham
Content Technologies Ltd
1220 Parkview
Arlington Business
Reading, RG7 4
United
Phone: +44 118 930 1300
Fax: +44 118 930 1301
EMail: GK@ACM.
Klyne Standards Track [Page 6]
RFC 2913 MIME Content in Media Feature Expressions September 2000
Appendix A: 'Type' feature tag
- Media Feature tag name(s):
- ASN.1 identifier associated with this feature tag
1.3.6.1.8.1.30
- Summary of the media features indicated
This feature tag indicates a MIME content type that a
agent is capable of handling, or that is contained within
message data
The content type consists of the MIME media type and subtype
presented using all lower case letters and with any
characters removed
- Values appropriate for use with this feature tag
- The feature tag is intended primarily for use in the
applications, protocols, services, or negotiation mechanisms
Any application that wishes to convey MIME content
information in a media feature expression
- Examples of typical use
(type="image/tiff")
(& (type="text/plain") (charset=US-ASCII) )
- Related standards or documents
MIME, RFC 2045 [7]
MIME, RFC 2046 [8]
Registration of Charset and Languages Media Features Tags [10]
- Considerations particular to use in individual applications
protocols, services, or negotiation mechanisms
(N/A
Klyne Standards Track [Page 7]
RFC 2913 MIME Content in Media Feature Expressions September 2000
- Interoperability considerations
String feature matching is case sensitive, so consistent use
case for content type values and parameters is essential
content type value matching is to be achieved in a
consistent with MIME content type matching
Similarly, white space must be used consistently
This registration specifies a canonical form to be used
content type values (lower case letters and remove
whitespace).
- Related feature tags
(N/A
- Intended usage
- Author/Change controller
Klyne Standards Track [Page 8]
RFC 2913 MIME Content in Media Feature Expressions September 2000
Full Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Klyne Standards Track [Page 9]
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