One area for TAG/IAB collaboration might be "extensibility" (including versioning, of course).
From: Bernard Aboba [mailto:bernard_aboba@hotmail.com]
Sent: Sunday, October 16, 2011 2:17 PM
To: duerst@it.aoyama.ac.jp; Larry Masinter
Cc: happiana@ietf.org
Subject: RE: [happiana] Policy for registries for extensibility points
> > d) If there is a registry, it is only useful if values are registered. A registry which does not match actual use (as with URI schemes, Media Types) is harmful.
[BA] This seems like an important point which might be worth making within an IAB document on the subject of extensibility (draft-iab-extension-recs). If people have suggested text (which might fit in Section 3.6), feel free to suggest it.