standards-track
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... top-level type can be
defined to accommodate it. Such a definition MUST be done via
standards-track RFC; no other mechanism can be used to define
additional top-level content types ...
... protocols must be respected when the specification of a media type is
part of a standards-track protocol. In addition, other standards
bodies making use of the standards tree may have their own rules
...
... registration of a top-level type requires
standards-track processing in the IETF and, hence, RFC publication.
...
... media types MUST have properly formed type and subtype names.
All type names MUST be defined by a standards-track RFC. All
type/subtype name pairs MUST be unique and MUST contain the proper
...