Fwd: [CF-metadata] Variable Associations (was CF convention for vector quantities)

[Jonathan Gregory]

Dear Bryan

I think that we don't need to build such structure into the data
which is written. Given that east/north and x/y components can be easily
identified by text substitutions in the standard names, it would be
straightforward to write a program to generate a list of the vector quantities
(i.e. the input file which Bert wants) from the standard name table. No extra
information is required to do this, so it would be an unnecessary complication
of the convention, I feel. We can provide such a list on the CF web site if
it's generally useful.

(The algorithm is that if you can find two names of the general form
[A_]eastward[_B] and [A_]northward[_B], where A and B are the same in the two
cases, they are components of a vector quantity A_B. Similarly with x and y
components.)

Factorising the standard name into bits has the effect of meaning more
attributes have to be checked by data-reading programs, and the data is more
complicated to write. I don't see an advantage in doing it except where the
bits might be multi-valued coordinates.

Best wishes

Jonathan