Dear Chris > 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).
Yes, I agree with that. However, if you're reading a CF file, you aren't just reading plain variables. If you're using/writing software which knows how to interpret the file following the CF convention, it should know what the "intent" is, in a CF context, of each of the variables of interest. For example, you know that an auxiliary coordinate variable of char data must be a vector of strings, and the trailing or only dimension is the max string length. If you came across this variable when scanning all the variables in a netCDF file, with no interest in CF, you wouldn't know that it was an array of strings, but if you are using it as a CF aux coord var, you do know that, so I don't think any further signal is needed - it would be redundant. Best wishes Jonathan ----- Forwarded message from Chris Barker <chris.bar...@noaa.gov> ----- > Date: Mon, 6 Mar 2017 11:16:35 -0800 > From: Chris Barker <chris.bar...@noaa.gov> > To: Jonathan Gregory <j.m.greg...@reading.ac.uk> > CC: "cf-metadata@cgd.ucar.edu" <cf-metadata@cgd.ucar.edu> > Subject: Re: [CF-metadata] Pre-proposal for "charset" > > On Mon, Mar 6, 2017 at 9:47 AM, Jonathan Gregory <j.m.greg...@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 > 7600 Sand Point Way NE (206) 526-6329 fax > Seattle, WA 98115 (206) 526-6317 main reception > > chris.bar...@noaa.gov ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
