[CF-metadata] subgrid variation

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 8 Feb 2005 08:54:19 +0000

Dear Steve

> They
> are now creating files which have "standard_name" attributes. In most cases they
> lack cell_methods attributes. They believe that they are creating CF 1.0
> compliant files. Does your proposal "(2)" imply that valid CF 1.0 files which
> use "standard_name" will become invalid CF 2.0 files? If so isn't this a serious
> backwards compatibility concern?

Yes, it would. Karl has also made that point. Strangely, Karl's posting doesn't
appear on the news archive.

I agree, we can only make cell_methods strongly recommended, rather than
mandatory, in order that previous CF files remain valid. I think that such a
recommendation is needed, because really people ought to record what they
intend a quantity to be, and when there is subgrid variation of surface types,
for instance, there is a real ambiguity. The standard name alone is not
sufficient metadata.

> Before we introduce further complexity to the sub-grid cell_methods machinery
> (which is not one of the more "transparent" aspects of CF already), has there been
> a serious exploration of alternatives?
...
> I'm tempted to think that a thoughtful discussion on how to systematize these
> modifiers is in order.

So far, I have not managed to think of better ways myself, and believe me, I
have spent hours thinking about it! But anyone's welcome to make proposals, of
course. Yes, the standard_name and its modifiers and the cell_methods together
specify the quantity. This is a step towards some "factorisation" of the
description, in order to limit the expansion of the standard name table, and I
think it's quite systematic. We are following a path between the extremes of
putting all the definition in one attribute, and breaking it down into many
attributes.

> Listening
> to the general community chatter there's no doubt that plenty of groups have
> picked up the "standard_name" attribute and are thrilled to have found it.

That is encouraging. Of course, it means we need to arrange ways of making it
easier to add and modify standard names. That's something I hope we can discuss
at the meeting at the GO-ESSP meeting at the BADC in June.

Best wishes

Jonathan
Received on Tue Feb 08 2005 - 01:54:19 GMT