Hi Jonathan:
Jonathan Gregory wrote:
> Dear all
>
> I confess to not having read what the user guide says (at least, not recently)
> and I have copied it below in case others would like to be reminded as well.
Russ and I are a bit unclear if there are older versions that say something different.
>
> This suggests that Nan's extra conventions for oceansites would correctly be
> denoted "CF-1.4/OceanSITES-1.0", since oceansites accepts all of CF and adds
> some more. We could, for instance, amend the CF convention to recommend this
> format for additional conventions that explicitly say they adopt all of CF
> and add some more. I am sure the checker could be amended to ignore whatever
> follows / in the Conventions attribute.
>
> As a matter of policy, I would hope that subconventions like this would only
> be added if the extra conventions were too application-specific to be of
> general use. New ideas which could apply in other areas could usefully be
> added to the main CF standard.
agree, we should encourage adding generally useful things to the core.
>
> The user guide doesn't say anything about spaces. It doesn't prohibit them,
> but it does talk about conventions names being filenames. Although filenames
> containing spaces are possible, they're a nuisance on Unix, and it seems to me
> they would be a hazard in this context. People often put in extra spaces, or
> leave out spaces, fairly arbitrarily in strings, and if they are significant
> that would be an error. Wouldn't it be better to recommend against spaces in
> conventions names in the netCDF user guide?
yes, i agree to recommend against spaces, just worried about whats already out there. in fact, a brief survey shows that I may be the main offender (sheepish grin)!
>
> This user guide convention with / is for subconventions. It doesn't deal with
> the situation where several separately developed conventions are being used,
> and you might want to put them in a blank-separated or comma-separated list.
> I don't think we should allow that in the Conventions attribute unless and
> until we'd decided how to resolve conflicts between these conventions. (There
> are no conflicts with a subconvention that explicitly accepts all the of the
> standard to which it is adding.)
i think the common use case is this: a group already has their data using their own convention, possibly even documented(!). now they want to get on the CF bandwagon so they are going to try to be CF compliant without breaking their existing software. I dont see how we can disallow that, since CF explicitly allows other metadata. if there are conflicts, then I agree this should not be allowed. it does argue for us to resolve the namespace problem, eg CF:attname = value.
>
> Best wishes
>
> Jonathan
>
>>From http://www.unidata.ucar.edu/software/netcdf/docs/netcdf.html#Attribute-Conventions
>
> If present, 'Conventions' is a global attribute that is a character array for
> the name of the conventions followed by the dataset, in the form of a string
> that is interpreted as a directory name relative to a directory that is a
> repository of documents describing sets of discipline-specific
> conventions. This permits a hierarchical structure for conventions and
> provides a place where descriptions and examples of the conventions may be
> maintained by the defining institutions and groups. The conventions directory
> name is currently interpreted relative to the directory
> pub/netcdf/Conventions/ on the host machine
> ftp.unidata.ucar.edu. Alternatively, a full URL specification may be used to
> name a WWW site where documents that describe the conventions are maintained.
>
> For example, if a group named NUWG agrees upon a set of conventions for
> dimension names, variable names, required attributes, and netCDF
> representations for certain discipline-specific data structures, they may
> store a document describing the agreed-upon conventions in a dataset in the
> NUWG/ subdirectory of the Conventions directory. Datasets that followed these
> conventions would contain a global Conventions attribute with value "NUWG".
>
> Later, if the group agrees upon some additional conventions for a specific
> subset of NUWG data, for example time series data, the description of the
> additional conventions might be stored in the NUWG/Time_series/ subdirectory,
> and datasets that adhered to these additional conventions would use the global
> Conventions attribute with value "NUWG/Time_series", implying that this
> dataset adheres to the NUWG conventions and also to the additional NUWG
> time-series conventions.
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Received on Thu Sep 03 2009 - 08:28:57 BST
