[CF-metadata] Pre-proposal for "charset"

Jonathan Gregory j.m.gregory at reading.ac.uk
Thu Feb 23 09:22:52 MST 2017


Dear Bob

> CF section 9.5 says: "The variable carrying the cf_role attribute may
> have any data type."
> And that makes sense, because some profile_id might be an integer and
> theoretically could be a single char.
>
>> Yes, I agree that on the basis of netCDF
>> alone
>> you can't tell whether it's a string or a 10-char array. However, the
>> cf_role
>> is a string-valued attribute, according to the CF convention, so it must
>> be a
>> string. I expect that for contents of netCDF files that follow the CF con-
>> vention this ambiguity shouldn't arise - but if there are cases where it
>> does
>> we should consider them.

Sorry. Being in a hurry, because you mentioned cf_role, I assumed you were
referring to the attribute, rather than the variable which has that attribute.

Looking again at the example you sent, I'd say that this file is not a proper
CF DSG file; it contains a number of variables which could be individual
timeseries, but they haven't been combined into a single data variable so
there is no element (or "station") dimension. The "timeseries" variable which
you asked about isn't referred to by any of the data variables. I agree that
its function is unclear, but I would say it's not CF-compliant anyway, so CF
doesn't need to provide an answer to this ambiguity. The file should look
like Example H3, H6 or H7 of the CF document.

Best wishes

Jonathan



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