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 provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 27, 2021. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Guy Expires April 27, 2021 [Page 1] Internet-Draft Media Types with Multiple Suffixes October 2020 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 1. 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. Guy Expires April 27, 2021 [Page 2] Internet-Draft Media Types with Multiple Suffixes October 2020 For example, a media type that uses the two suffixes "+svg+xml" is only permitted insofar as "svg+xml" is already registered. 2. 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, . [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . 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/ Guy Expires April 27, 2021 [Page 3]