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

Chris Barker chris.barker at noaa.gov
Mon Mar 6 12:16:35 MST 2017


On Mon, Mar 6, 2017 at 9:47 AM, Jonathan Gregory <j.m.gregory at reading.ac.uk>
wrote:

> Yes, we can reopen the ticket. I think the _Encoding for char is a good
> idea,
> especially if it's an NUG convention.


so let's do that part at least.

> Are there any files out in the wild that DO use ND arrays of NC_CHAR that
> > are not intended to be interpreted as a (N-1)D array of Strings?
>
> That is the question. In particular, since this the CF convention we're
> talking about, are there any char arrays which are part of CF,


indeed.


> where the
> intent is not clear?
>

We need to be "clear" about what we mean by "the intent is clear". I think
that much of the point of CF is to be as explicit as possible, -- i.e. the
reader of a CF file should not have to know anything about how given data
tends to be used in order to determine what data type an array should be
(or what shape it should be).

I saw this an an author of sometimes generic tools -- the tool should be
able to read the file, and produce the appropriate native array for the
task at hand, without knowing something like: "ahh, this is the ID of a
Acme-ocean-widget -- those use char IDs -- so this must be a char" --
Humans can do that -- software can't (not easily anyway!)

And clearly specifying whether a char array is a char array or a string
array will better unify netcdf3 and netcdf4.

netcdf4 can be explicit about it -- netcdf3 can't -- so it'd be nice if CF
could fill that gap.

Now that I think about it, this really should be a netcdf convention --
like _FillValue, but this is a CF list....

-CHB

-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
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Chris.Barker at noaa.gov
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