On Media-Types, Content-Types, and related terminology
draft-bormann-core-media-content-type-format-01

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Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Intended status: Standards Track                           July 08, 2019
Expires: January 9, 2020

         On Media-Types, Content-Types, and related terminology
            draft-bormann-core-media-content-type-format-01

Abstract

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

   This memo is an attempt at clearing it up.

Status of This Memo

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   This Internet-Draft will expire on January 9, 2020.

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Table of Contents

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

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:

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

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

2.  Media-Type

   However, the term "media type" is now generally used for a registered
   combination of a type-name and a subtype-name.  We further
   disambiguate by calling this a media type name, as, in ABNF:

   Media-Type-Name = type-name "/" subtype-name

   For the purposes of this memo, we define:

   Media-Type-Name:  A combination of a type-name and a subtype-name
      registered in [IANA.media-types], conventionally identified by the
      two names separated by a slash.

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   (This leaves the term "Media Type" for the actual specification that
   is registered under the Media-Type-Name.)

3.  Content-Type

   Media types have parameters [RFC6838], some of which are mandatory.
   In HTTP and many other protocols, these are then used in a "Content-
   Type" header field.  HTTP [RFC7231] uses:

      Content-Type = media-type
      media-type = type "/" subtype *( OWS ";" OWS parameter )
      type       = token
      subtype    = token
      token          = 1*tchar
      tchar          = "!" / "#" / "$" / "%" / "&" / "'" / "*"