This draft is looking better than the first two.  It's in line with the other structured syntax suffix drafts.  The only comment I have is:

Page 4, IANA Considerations, Contact name: The description of that email address (art@ietf.org) is “Applications and Real-Time Area Discussion”, not "Applications and Real-Time Area Working Group".  It’s not a WG that I am aware of.  Did you want this to use this address or might you prefer appsawg?  APPSAWG is listed as the “ART Area General Applications Working Group”.  RFC 6839 references “Apps Area Working Group (apps-discuss@ietf.org)” in its IANA Considerations section, so I can see how you might have gotten to what you used, but I don't think that's correct.  Give some consideration to the right name and email address for this item and the Author/Change controller.