Network Working Group                                             A. Guy
Internet-Draft                                            Digital Bazaar
Intended status: Standards Track                        October 24, 2020
Expires: April 27, 2021


                   Media Types with Multiple Suffixes
          draft-w3cdidwg-media-types-with-multiple-suffixes-00

Abstract

   This document updates RFC 6838 "Media Type Specifications and
   Registration Procedures" to describe how to interpret subtypes with
   multiple suffixes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 27, 2021.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Media Types with Multiple Suffixes  . . . . . . . . . . .   2
   2.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   3

.  Introduction

   As written, RFC 6838 [RFC6838] permits the registration of media type
   subtype names which contain any number of occurrences of the "+"
   character.  RFC 6838 defines the characters following the final "+"
   to be a structured syntax suffix, but does not define anything
   further about how to interpret subtype names containing more than one
   "+" character.

   This document updates RFC 6838 to clarify how to interpret subtype
   names containing more than one "+" character as subtypes with
   multiple suffixes.

   As registration of media types which use a structured suffix has
   become widely supported, this enables further specialization of media
   types that build on already registered and well-defined media types
   which themselves use a structured suffix.

1.1.  Media Types with Multiple Suffixes

   The following paragraphs are additions to RFC 6838.

   Media types MAY be registered with more than one suffix appended to
   the base subtype name.  The suffixes MUST be interpreted as ordered,
   starting with the most specific (the base subtype name) on the left,
   to the most generic on the right.  Characters before the first "+" in
   a subtype name specify the base subtype name.  Characters following
   each subsequent "+" in a subtype name denote additional syntax
   specifier suffixes.

   This means that receivers of the media type can do generic processing
   on the underlying representation according to their ability to
   process any subset of the right-most suffix(es) in cases where
   specific handling of the exact media type is not required.

   Media types with more than one suffix MUST be registered according to
   the procedure defined in [RFC6838] with the additional requirement
   that each subset of suffixes, starting from the right-most suffix,
   MUST be individually registered as a subtype in its own right.




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   For example, a media type that uses the two suffixes "+svg+xml" is
   only permitted insofar as "svg+xml" is already registered.

.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

Appendix A.  Acknowledgements

   The editors would like to thank the following individuals for
   feedback on and implementations of the specification (in alphabetical
   order):

Author's Address

   Amy Guy
   Digital Bazaar
   203 Roanoke Street W.
   Blacksburg, VA  24060
   US

   Email: rhiaro@digitalbazaar.com
   URI:   https://rhiaro.co.uk/




















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