[CF-metadata] Convention attribute

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 28 Dec 2011 22:22:19 +0000

Dear Mark and Dave

I agree with Dave's answers. If two conventions are used together, it is the
responsibility of the data-writer to guarantee that the metadata supplied is
consistent if there are any overlaps in meaning. A particular case of that is
if the two conventions define attributes with the same names. It has been
suggested that conventions could signal their own name-spaces e.g. CF
attributes could all be prefixed with "cf_" (like the cf_role attribute, which
has been introduced in the new CF section 9). That could help with preventing
collisions of namespaces, but

* it would be cumbersome for writers of files that adhere to only one
convention, which is the usual case, and awkward for programs that read files,
since they would have to check for every attribute by two different names
(with and without the prefix, considering all the data that already exists
without prefixes).

* it doesn't help if the two conventions are inconsistent in their metadata,
whether or not they use similarly named attributes, and this is the more
serious problem, I would argue.

Therefore I don't think this is really a magic solution to get rid of the
potential difficulty. Rather, the writers of conventions have to be aware of
other netCDF conventions that might be used with theirs, and try to use ones
that already exist instead of defining new ones for a given purpose.

Best wishes

Jonathan
Received on Wed Dec 28 2011 - 15:22:19 GMT