[CF-metadata] some concerns about the "ensemble axis" proposal

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 22 Mar 2007 22:51:03 +0000

Dear Steve

You make a specific suggestion that we could use a mandatory axis attribute to
identify ensemble axes. I think that's a useful idea. Although it should not be
difficult to use such an axis when you know which one it is, I agree that
identifying it could be tricky.

You express many other concerns about the CF standard and its development. My
perception is quite different from yours. I think we have been rather careful
about the additions we make. It is not my impression that the standard has
suffered from "instability and snow-balling complexity". We only add things
that people need. In doing that, we should try to anticipate obvious next steps
and generalisations which are very likely to be needed, but I do not think we
should hold up development because we cannot see the way to an all-encompassing
solution. Also, I don't understand the problem about unintelligibility by
existing applications. Pretty much all of CF is optional; only the COARDS core
is not. Old applications should simply be able to ignore new parts. They won't
be able to understand them, but they should not be broken by them. I think the
only significant departure from COARDS is the one which perhaps worries you
viz. in CF 2.4:

"A variable may have any number of dimensions, including zero, and the
dimensions must all have different names. COARDS strongly recommends limiting
the number of dimensions to four, but we wish to allow greater flexibility."

Even COARDS does not forbid more than four dimensions. CF has had this
statement allowing more than four from its early drafts, whenever that was -
probably more then seven years ago - so suggesting a possible fifth dimension
for ensembles is hardly an innovation now.

I agree with you that it is difficult to know we are making the best decisions
if few people express a view. On this particular thread (about the ensemble
axis) an unusually large number of people have expressed views, and that's
good. I would say there is a majority in favour of the proposal among those
who have contributed, but unanimity would be better than a majority. This is
not a new problem. We have convened the committees partly to engage more
people in the process. It could be that the silent majority sees no particular
problem with the proposal.

My concern is that our decision-making presently is terribly slow. We have not
definitely enacted any change for more than three years, although we have in
effect agreed several on the email list. I don't think that's satisfactory. I
will try to find time to repropose the apparently agreed versions of some of
them through the Trac system, so that we have them clearly visible. But we do
need to agree reasonable timescales for making decisions, I think.

Best wishes

Jonathan
Received on Thu Mar 22 2007 - 16:51:03 GMT