On Media-Types, Content-Types, and related terminology
draft-bormann-core-media-content-type-format-02

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Network Working Group                                         C. Bormann
Internet-Draft                                    Universität Bremen TZI
Intended status: Standards Track                          18 August 2020
Expires: 19 February 2021

         On Media-Types, Content-Types, and related terminology
            draft-bormann-core-media-content-type-format-02

Abstract

   There is a lot of confusion about media-types, content-types, and
   related terminology.

   This memo is an attempt at clearing it up, so we can use consistent
   terminology in CoRE and related specifications.  It also defines some
   ABNF that can be used in these specifications.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 19 February 2021.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Media-Type  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Content-Type  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Content-Coding  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Content-Format  . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Abbreviations . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [RFC1590] introduced media types and their registration.  That
   document took MIME types from [RFC1521] and gave them a new name.  At
   that time, the term "media type" was often used just for the major
   type ("text", "audio"), and what we call a media-type now was the
   combination of a type and a subtype.  This lives on in [RFC6838],
   which does not even have an ABNF [RFC5234] production for media type.
   [RFC6838]'s predecessor, [RFC4288], supplied the ABNF shown in
   (Figure 1).

                 type-name = reg-name
                 subtype-name = reg-name

                 reg-name = 1*127reg-name-chars
                 reg-name-chars = ALPHA / DIGIT / "!" /
                                  "#" / "$" / "&" / "." /
                                  "+" / "-" / "^" / "_"

             Figure 1: ABNF for type and subtype, from RFC 4288

   [RFC4288] contains the semantically equivalent ABNF in Figure 2,
   which also provides comments that limit the use of "." and "+".

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   type-name = restricted-name
   subtype-name = restricted-name

   restricted-name = restricted-name-first *126restricted-name-chars
   restricted-name-first  = ALPHA / DIGIT
   restricted-name-chars  = ALPHA / DIGIT / "!" / "#" /
                            "$" / "&" / "-" / "^" / "_"
   restricted-name-chars =/ "." ; Characters before first dot always
                                ; specify a facet name
   restricted-name-chars =/ "+" ; Characters after last plus always
                                ; specify a structured syntax suffix