Internet Media Type for DFXP

While updating the list of media types related assigned to W3C [1], I
noticed that DFXP [2] does not define an Internet Media Type (s?).
Note that "W3C Working Groups engaged in defining a language SHOULD
arrange for the registration of an Internet Media Type [3]". Unless the
media type defintion are added into the specification, the Working Group
will need to produce an RFC in order to register them with IANA (ie the
Group will need to follow the old procedure in [1]).

Regards,
Philippe

[1] http://www.w3.org/2002/06/registering-mediatype
[2] http://www.w3.org/TR/ttaf1-dfxp/
[3] http://www.w3.org/2001/tag/2002/0129-mime#registration