Maybe it?s way too late now, but why does the data model have to allow only
one attribute: global or variable?
Why not simply keep the distinction between variable and global attributes?
That is, global attributes apply to the entire dataset, and variable
attributes apply to each variable.
So if there is a global attribute ?global1?, it applies to variable_a, but
you don?t say that variable_a has that attribute at all.
-CHB
On Mar 15, 2019, at 5:48 AM, B?rring Lars <Lars.Barring at smhi.se> wrote:
Dear all,
I have come across many CMIP5 files that have the same attribute [name]
attached to the data variable as found in the globals.
In particular it seems that CMOR was writing variable processing history
attached to the variable, and more general file processing in the global
history.
I have also seen that "comment" sometimes occur both as global and as
variable attribute.
If such a duplication occurs, CF writes:
"When an attribute appears both globally and as a variable attribute, the
variable?s version has precedence."
My interpretation of this is that if there are contradictory information
then the variable's attribute has precedence, but otherwise it does not
invalidate or overshadows what is in the global attribute.
However, the data model presented in the GMD paper (
https://www.geosci-model-dev.net/10/4619/2017/ page 4629, [page 11], under
"4.1 The field construct") presents a more restrictive interpretation:
"In the data model, we consider that netCDF global file attributes apply to
every data variable in the file, except where they are superseded by netCDF
data variable attributes with the same name."
I understand this to mean that if the same attributes (e.g. comment or
history) is present both as global and variable attribute, then the global
attribute is overshadowed (as if it did not exist at all)?
Is this correct? If so, is this the best solution?
Would not concatenating the information contained in each (putting the
variable text first) be a more appropriate way to resolve the situation
(and thus specify in the data model)?
Kind regards,
Lars
--
Lars B?rring
FDr, Forskare
PhD, Research Scientist
SMHI / Swedish Meteorological and Hydrological Institute
Rossby Centre
SE - 601 76 NORRK?PING
http://www.smhi.se
E-post / Email: lars.barring at smhi.se
Tel / Phone: +46 (0)11 495 8604
Fax: +46 (0)11 495 8001
Bes?ksadress / Visiting address: Folkborgsv?gen 17
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