[CF-metadata] CF Standards

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 24 Feb 2011 12:36:53 +0000

Dear Karl et al.

I think there are several separate points here!

* If the standard_name attr contains the "count" modifier, the quantity is
dimensionless. The checker should take standard_name modifiers into account
(Appendix C) as well as the canonical units from the standard name table
(and the cell_methods) when deciding what units a quantity can have. This is
not explicitly stated in the conformance document, but it should be. I will
create a trac defect ticket for that.

*> I think it is wrong to add a "bounds" attribute to a formula term
> attached to a vertical coordinate. Only the coordinate itself
> should have a bounds attribute.

The CF standard doesn't clarify that. It doesn't say whether formula terms
can have bounds, or whether bounds can have formula terms, or both. If both,
then they have to be consistent somehow. We should clarify this, I think.
You think bounds should have formula terms (if applicable) but not vice-versa,
is that right? What does anyone else think?

*> The reason this seemed to fix the problem is presumably that the CF
> checker does not require (or look for?) units to be attached to
> bounds variables; the units are by convention the same as the
> coordinate variable itself.

In fact the conformance document says

"If a boundary variable has units or standard_name attributes, they must agree
with those of its associated variable."

which seems fine to me. If it doesn't have them, they are implied to be the
same as the coord var itself, as you say.

Best wishes

Jonathan
Received on Thu Feb 24 2011 - 05:36:53 GMT