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

Bob Simons - NOAA Federal bob.simons at noaa.gov
Mon Feb 27 18:43:39 MST 2017

CF section 2.2 already clarifies that it is the "last" (AKA "rightmost")
dimension that specifies the maximum number of characters and is collapsed
to interpret the char array as a String array:
> An n-dimensional array of strings must be implemented as a character array
> of dimension (n,max_string_length), with the last (most rapidly varying)
> dimension declared large enough to contain the longest string in the array.
> All the strings in a given array are therefore defined to be equal in
> length. For example, an array of strings containing the names of the months
> would be dimensioned (12,9) in order to accommodate "September", the month
> with the longest name.

My proposed change does not alter that text.

On Mon, Feb 27, 2017 at 4:58 PM, Chris Barker <chris.barker at noaa.gov> wrote:

> On Wed, Feb 22, 2017 at 11:38 AM, Bob Simons - NOAA Federal <
> bob.simons at noaa.gov> wrote:
>>> We need to either specify the "string" dimension, or have a consistent
>>> convention:
>>> A 10x8 CHAR array could be either 10 8 character strings or 8 ten
>>> character strings. And it gets more confusing with higher dimensions.
>> There is no standard naming system in CF to denote a String dimension
>> (ie, the number of chars, vs a char array). That is a different approach to
>> solving the problem. I don't like that approach as much because so many
>> people have written so much software that writes and reads files using
>> dimension names of their choice. I don't want to tell everyone to rewrite
>> all their exiting files and software/scripts to read/write those files in
>> order to comply with new CF rules.
>> Instead, I'm proposing a separate, new attribute (data_type=string|char),
>> partly because it doesn't interfere with existing dimension names or
>> attribute names.
> I wasn't clear -- even if you know a CHAR array is supposed to be an array
> of strings, you don't know which dimension is the "string" dimension, and
> which is the array dimension. If you have a 3x4 array of length-5 strings,
> what is your CHAR array dimension? either of these would make sense:
> (3,4,5)
> (5,3,4)
> and
> (3,5,4) would be possible, though a bit insane :-)
> even worse, if you see a "string" array that has dimensions of (3,4,5)
> what is that? and (3,4) array of length-5 strings? a (4,5) array or length
> 3 strings?
> -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.Barker at noaa.gov


Bob Simons
IT Specialist
Environmental Research Division
NOAA Southwest Fisheries Science Center
99 Pacific St., Suite 255A      (New!)
Monterey, CA 93940               (New!)
Phone: (831)333-9878            (New!)
Fax:   (831)648-8440
Email: bob.simons at noaa.gov

The contents of this message are mine personally and
do not necessarily reflect any position of the
Government or the National Oceanic and Atmospheric Administration.
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