Dear Jonathan and Martin,
What I was trying to do here was legitimise an already established practice in
at least two communities in the observational oceanographic domain with
thousands of files in existence with the non-standard usage of the Conventions
attribute. I also carried the practice over into the specification of the
SeaDataNet NetCDF generation tool. I can see absolutely no benefit in pushing
through a new attribute for this purpose and so will circumvent the compliance
issue for SeaDataNet by moving the variable attribute into our namespace (i.e.
calling it SDN_Conventions). This leaves Derrick's glider community in the
lurch, but I suggest they either follow us or follow whatever solution the
European GROOM glider community adopts.
Martin's comments on namespace highlight a concern I identified whilst doing
the research for the SeaDataNet specification. Several communities have added
large numbers of both global and variable attributes with no indication of
namespace. Not only does this make it difficult to tease out what is CF and
what is a community extension, but it creates an accident in waiting. What
happens if CF creates a new attribute with a name already in community usage?
In my view it's too late to introduce a CF namespace and prefer the idea that
for a CF-compliant file CF should be the default namespace, with communities
taking responsibility for their extensions. This is what I've done for
SeaDataNet.
Cheers, Roy.
________________________________________
From: CF-metadata [cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Schultz,
Martin [m.schu...@fz-juelich.de]
Sent: 24 January 2013 18:54
To: cf-metadata@cgd.ucar.edu
Subject: Re: [CF-metadata] Usage of the 'Conventions' attribute (Nan
Galbraith)
Dear all,
I fully agree with Jonathan's view that it would not be a good idea to call
this new thing "Convention". On the other hand, I don't really like the term
"flag_convention_name" either, because it doesn't tell me anything. If I
understand correctly, then your desire is different from defining a pointer to
controlled vocabulary. Should it be a similar idea, then I suggest we should
try to follow the ideas and namings of ISO19115 (without being able to tell you
right away what the appropriate term would be). If it's cf specific and indeed
refers to the version of a cf document (or annex or whatever), shouldn't the
attribute then have a name that starts with "cf_"? E.g. cf_attribute_convention
?
Cheers,
Martin
Message: 4
Date: Thu, 24 Jan 2013 12:23:33 +1100
From: Jonathan Gregory <j.m.greg...@reading.ac.uk>
To: cf-metadata@cgd.ucar.edu
Subject: [CF-metadata] Usage of the 'Conventions' attribute
Message-ID: <20130124012333.gc22...@met.reading.ac.uk>
Content-Type: text/plain; charset=us-ascii
Dear Roy
I understand the need but I tend to think this would not be an appropriate
use of the Conventions attribute, which is a general netCDF attribute, not
specific to CF, and refers to files. I do appreciate the logical similarity
but I would have thought it better to define something more specific in CF
for this purpose.
If this is a need which several users have and is required for exchange of
data, then it is reasonable to propose to add something to CF. Since it's
an extra piece of information referring to flags, maybe an attribute such as
flag_convention_name would work? We could make it a requirement that this
attribute was allowed only if the variable had flag_meanings as well, to
prevent its being used as a substitute for spelling out what the flags mean
(as is necessary for the file to be self-describing).
Best wishes
Jonathan
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