[CF-metadata] "positive" attribute

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 28 Jun 2007 17:57:05 +0100

Dear all

I'm not arguing for inertia per se. My argument is that we haven't got a
problem with the present approach. Despite the philosophy about not trying to
design the future, I do also agree that we should look forward to obvious
developments.

So far as I can see the future (not very far, perhaps :-) it doesn't look like
this is going to be a problem for carbon-cycle or chemistry names. We have
already had quite a lot of discussion of chemistry names. The concepts that
have so far been discussed, such as emission and deposition, don't need their
sign-convention stated, any more than we need to state the sign for
evaporation, precipitation, air pressure, windspeed or temperature. I think
this is the case for most quantities, so we can just make it clear for ones
that are ambiguous. If we change our minds later, we can do so using aliases.

Another point is that there is no generic concept of a sign convention. For
vertical fluxes it is up/down, for zonal quantities east/west, for the
biosphere it is in/out, for the atmosphere the same carbon fluxes would
be out/in, for bearings it is clockwise/anticlockwise, for tensors there are
two signs. Hence the permitted values of a sign attribute would depend on the
standard name. This is not a category which can be cleanly factorised (unlike
cell_methods and coordinates).

Indeed files can be repaired after they have written, whether that it is to
change standard names or add an attribute. But that is more work which might
well not be done. CF compliance is not legally enforceable, after all.

Best wishes

Jonathan
Received on Thu Jun 28 2007 - 10:57:05 BST