Hi all,
There seem to be a need for upgrading the text in the CF Conventions
documents about the global "Conventions" attribute. I am thinking of
paragraph 2.6.1 "Identification of Conventions", which seems to have
remained unchanged (except for different Conventions version numbers)
throughout the history of CF.
The text in the CF 1.4 document says: 'We recommend that netCDF files
that follow these conventions indicate this by setting the NUG defined
global attribute Conventions to the string value "CF-1.4" .'
According to the Unidata web page on NetCDF Conventions
(http://www.unidata.ucar.edu/software/netcdf/conventions.html),
specifying multiple conventions (either space separated or comma
separated) in this attribute is allowed. But the text above seems to
indicate that "CF-1.4" should be the only "recommended" value. My
impression, by sporadically following this mail list, is that this
restriction has never been intended, and that other additional
conventions are allowed in the Conventions attribute.
The reason I am raising this issue is an E-mail exchange on the THREDDS
E-mail list (subject "NcML and the <geospatialCoverage> element",
http://www.unidata.ucar.edu/mailing_lists/archives/thredds/2010/subject.html).
See specifically the discussion from January 21 and on. Some confusion
obviously exist on what actually are required by CF.
Further down in the same 2.6.1 paragraph I discovered another problem.
From the document: "The string is interpreted as a directory name
relative to a directory that is a repository of documents describing
sets of discipline-specific conventions. The conventions directory name
is currently interpreted relative to the directory
pub/netcdf/Conventions/ on the host machine ftp.unidata.ucar.edu."
There is no reference to CF on
ftp://ftp.unidata.ucar.edu/pub/netcdf/Conventions/.
Best regards,
Egil Støren
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