Indicating Media Features for MIME Content
RFC 2912

Document Type RFC - Proposed Standard (September 2000; No errata)
Last updated 2013-03-02
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Network Working Group                                           G. Klyne
Request for Comments: 2912                          Content Technologies
Category: Standards Track                                 September 2000

               Indicating Media Features for MIME Content

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   In "A Syntax for Describing Media Feature Sets", an expression format
   is presented for describing media feature capabilities using simple
   media feature tags.

   This memo defines a Multipurpose Internet Mail Extensions (MIME)
   'Content-features:' header that can be used to annotate a MIME
   message part using this expression format, and indicates some ways it
   might be used.

Klyne                       Standards Track                     [Page 1]
RFC 2912       Indicating Media Features for MIME Content September 2000

Table of Contents

   1. Introduction ...............................................  2
      1.1 Terminology and document conventions ...................  2
   2. Motivation and goals .......................................  3
   3. The 'Content-features:' MIME header ........................  4
      3.1 Whitespace and folding long headers ....................  4
      3.2 Usage considerations ...................................  4
        3.2.1 Simple message parts ...............................  4
        3.2.2 Multipart and other composites .....................  5
        3.2.3 Reference to external data .........................  5
   4. Examples ...................................................  5
      4.1 Simple message .........................................  5
      4.2 Fax message ............................................  6
      4.3 Multipart/alternative data .............................  6
      4.4 Reference to external message data .....................  8
      4.5 Compressed data ........................................  8
      4.6 Multipart/related data .................................  8
   5. Security Considerations ....................................  9
   6. Acknowledgements ........................................... 10
   7. References ................................................. 10
   8. Author's Address ........................................... 10
   Full Copyright Statement ...................................... 11

1. Introduction

   In "A Syntax for Describing Media Feature Sets" [1], an expression
   format is presented for describing media feature capabilities as a
   combination of simple media feature tags, registered according to
   "Media Feature Tag Registration Procedure" [2].  This provides a
   format for message handling agents to describe the media feature
   content of messages that they can handle.

   This memo defines a MIME 'Content-features:' header that can be used
   to annotate a MIME message part using these feature expressions.
   This header provides a means to indicate media-related features of
   message content that go beyond the MIME content type.

   Consideration is also given to how it may be used to present message
   media content information that is problematic to express within the
   basic MIME framework.

1.1 Terminology and document conventions

   This section defines a number of terms and other document
   conventions, which are used with specific meaning in this memo.

Klyne                       Standards Track                     [Page 2]
RFC 2912       Indicating Media Features for MIME Content September 2000

   media feature
         information that indicates facilities assumed to be available
         for the message content to be properly rendered or otherwise
         presented.  Media features are not intended to include
         information that affects message transmission.

   feature set
         some set of media features described by a media feature
         assertion, as described in "A Syntax for Describing Media
         Feature Sets" [1].  (See that memo for a more formal definition
         of this term.)

   feature set expression
         a string that describes some feature set, formulated according
         to the rules in "A Syntax for Describing Media Feature Sets"
         [1] (and possibly extended by other specifications).
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