[CF-metadata] Convention attribute

From: Dave Allured <dave.allured>
Date: Wed, 28 Dec 2011 13:07:09 -0700

Mark,

That is an important question. I suggest that there is only one
practical interpretation for multiple conventions: 100 percent
compiance with the requirements of each listed convention. This leads
to immediate answers for your questions, as follows.

On Wed, Dec 28, 2011 at 9:59 AM, Hedley, Mark
<mark.hedley at metoffice.gov.uk> wrote:
>
> I am interested in the implications for defining multiple conventions in the same file. ?As a data creator, what am I asserting by defining my file with multiple conventions?
>
> It could be said that the conventions attribute provides an implicit name space for the controlled terms it defines. ?This enables a data consumer to assign meaning to the terms defined by the convention which exist within a particular file.
>
> If I have one convention, I can pattern match all the attributes and explicitly link them to a convention. ?All the ones that don't match are user defined, and not part of the convention. ?Does this scale to having multiple conventions defined?

Yes, assuming that there are no incompatibilities between attributes
in use in any given file.

> Do conventions maintain mutually exclusive vocabularies? I don't think they do.

Agreed. Each shared term must be used in a mutually compatible way,
or else it must not be used in the context of two incompatible
definitions.

> Where vocabularies share terms, is there oversight that ensures that shared terms are defined the same way?

Only good judgement on the part of convention designers. In my
limited experience, there are a few popular conventions that have had
considerable influence on the development of other conventions. This
helps to engender conforming usage of attributes. Such conventions
include Unidata's attribute recommendations (mainly User's Guide
appendix B), COARDS, and CF; perhaps others.

> If I assert that two conventions are being used, does that mean that I have checked that my file contains no attributes which are ambiguously defined?

Not necessarily that checks were actually performed, but only that you
are asserting full compliance with each convention.

> If I want to use a term which is ambiguously defined, can I do this effectively?

By "ambiguously defined" do you mean defined incompatibly between two
conventions? I would say No, this would not be allowed if your goal
is to have the term interpreted unambiguously by all possible readers.

> There seems to be significant potential for confusion here; I think care is required.

Requiring independent conformance with each listed convention should
alleviate confusion.

--Dave
Received on Wed Dec 28 2011 - 13:07:09 GMT