On Media-Types, Content-Types, and related terminology
draft-bormann-core-media-content-type-format-00

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Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Intended status: Standards Track                          March 11, 2019
Expires: September 12, 2019

         On Media-Types, Content-Types, and related terminology
            draft-bormann-core-media-content-type-format-00

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 September 12, 2019.

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Table of Contents

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

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 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, as in

   Media-Type = type-name "/" subtype

   For the purposes of this memo, we define:

   Media-Type:  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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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          = "!" / "#" / "$" / "%" / "&" / "'" / "*"
                  / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
                  / DIGIT / ALPHA
   OWS        = *( SP / HTAB )

   We don't follow the inclusive use established by [RFC2616], parts of
   which became [RFC7231], to use the term media-type for a Media-Type