[CF-metadata] Reverse-time trajectory

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 1 May 2012 22:23:42 +0100

Dear Steve

> As the famed Henning piece on CORBA stated -- in standards
> committees "no" is a preferable answer to "yes" all other things
> considered. More generality can often lead to less
> interoperability in CF or other data standards.

I think that's too negative myself. CF is successful partly because it tries
to accommodate what people want to do, by and large, usually with existing
mechanisms, sometimes with new ones. This is more effective for encouraging
take-up of a standard than it would be to tell people what they have to do.
I agree that "No" is the starting-point when we have a proposal to add or
change conventions; there has to be a good reason for adding more complexity,
and even more for breaking backward compatibility. However, what is already
permitted by the standard is surely OK, isn't it, even if it is unusual. CF
has always permitted coordinate axes to run in either sense, and never said
anything special about time in that respect. I see no reason why a time
coordinate axis shouldn't run backwards, just as a latitude axis could be
N-S or S-N. Apart from Richard's example, paleoclimate timeseries often have
backward time axes.

Richard asked about discrete sampling geometries in particular. Here, there
is a question whether we really need to require time to run forwards in the
new representations (orthogonal multidimensional and ragged representations).
It would be interesting to know what John thinks, since his software is
probably the most widely used implementation of sect 9.

Best wishes

Jonathan
Received on Tue May 01 2012 - 15:23:42 BST