[CF-metadata] Taxa in CF. Some questions

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 2 Apr 2013 17:38:19 +0100

Dear Roy

Yes, I think you are right that it is useful to have the taxon as a dimension
because it allows you to put several of them in one variable, provided it's
the same quantity, with the same generic standard name. That is just like
bundling up timeseries from different locations into one data variable. This
kind of dimension is called a "discrete axis" in CF 1.6, section 4.5. By
"container variable" CF so far means something different: that's an empty
data variable which exists to hang attributes from, to specify grid_mappings.

I assume that MAXT is the size of the time dimension, isn't it? Could we write
your example like this:

dimensions;
  time=1000;
  string80=80;
  taxon=2;
variables:
  float abundance(time,taxon);
    abundance:standard_name="number_concentration_of_taxon_in_sea_water";
    abundance:coordinates="taxon_identifier taxon_name";
  char taxon_name(taxon,string80);
    taxon_name:standard_name="taxon_name";
  char taxon_identifier(taxon,string80);
    taxon_name:standard_name="taxon_identifier";

I am not sure if I've understood your example, though. Yes, I think both the
taxon descriptions should be string-valued auxiliary coordinate variables, as
I have shown them (CF section 6.1).

If there is only one taxon, the taxon dimension could be omitted.

However, I am a bit disturbed to learn that the taxon_name might not be
reliable or unique. If CF is going to depend on an external vocabulary, I would
argue that it needs one which provides unique and reliable self-describing
identifiers.

Best wishes

Jonathan
Received on Tue Apr 02 2013 - 10:38:19 BST