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-bounces at cgd.ucar.edu] On Behalf Of Schultz, Martin [m.schultz at fz-juelich.de]
Sent: 24 January 2013 18:54
To: cf-metadata at 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.gregory at reading.ac.uk>
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Usage of the 'Conventions' attribute
Message-ID: <20130124012333.GC22156 at 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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Received on Mon Jan 28 2013 - 01:11:09 GMT
