I've just been alerted (thanks Peter) to a problem in the teibare.odd 
which appears in the current TEI/exemplars directory (and is part of the 
oxygen TEI framework, updated at each release).

According to the text of the ODD "Finally three of  the TEI attribute 
classes are simplified. The attributes xml:space, rend, and xml:base
are removed from the class, so that this now makes available 
to all elements only the following attributes: <att>xml:id</att>, 
<att>n</att>, and
<att>xml:lang</att>. " But of course this is no longer true, because 
@rend is now supplied by rather than by 
(along with a lot of other weird attributes which weren't there before).

One solution might be to tie this ODD explicitly to a much earlier 
release of the Guidelines by means of a @source parameter. That would 
test whether all the tools in the processing chain Do The Right Thing in 
such a case.

Another might be to bring the ODD up to date, e.g. by deleting the class. That would probably be less upsetting for 
existing tools.

Or we could just leave well alone, and be prepared to shrug when people 
complain that TEI Bare is really not as bare as it claims to be...