Hi Jonathan
Thanks for doing this. I think it's an important step.
Unequiviocally: CF needs an explict data model, independent of netCDF!
My take on this is that the right way to go forward is to produce an
abstract description (aka a data model) for CF as is now - which means
it explicitly includes NetCDF dependencies.
Then we explicity identify those dependencies (and assumptions) and
identify the underlying data model.
In doing so, I think we want to use *existing* data modelling tools and
language, rather than inventing our own.
I had a stab at this a few years ago, an image of which is attached. I
know it's wrong in a couple of details, but I never got back to finish
it. Had I done so, I would have documented (*) it and shared it with the
CF community. then.
(* by which I mean, explain in more neutral langauge what the UML was
intended to convey).
With those thoughts in mind, a couple of comments on your web page.
Firsty, and most importantly, most of the important ideas are there, and
I think it's a great start. however, it's in the nature of these things
to criticise:
- I don't like the concept of a space construct. It's a new term to me
which doesn't carry any useful attributes. I much prefer the use of
object, which *is* a language neutral term (in data modelling). If you
use object, you can then use existing data modelling tools and
voabularies.
-I don't like central assumptions that are violated. Either we make it
or we don't. You can make that assumption property of some attributes of
space constructs.
- I think text without pictures is just as unhelpful as pictures without
text (my version :-).
With my last point in mind, and in an effort to be constructive: howabout
I spend an afternoon with you, and see if we can get my picture and your
text congruent? We might as well exploit our geographic adjacency :-)
Cheers
Bryan
> Dear all
>
> Although CF is primarily a file format convention, we often have in
> mind a logical data model for CF data while we are discussing
> modifications and extensions to CF. In principle the data model can
> be separated from the mechanics, restrictions and requirements of
> netCDF itself, and could apply to other file formats. In
> http://www.met.rdg.ac.uk/~jonathan/CF_metadata/cfdm.html I have
> outlined my perception of the CF data model. I know this is not the
> only such description. For example, libcf implicitly has a CF data
> model, but it is generally more low-level, it seems to me. I may
> well be completely unaware of other relevant documents, and I'd be
> grateful to hear of them, and in any case for comments on my version
> of the data model. Would it be useful to write down a data model as
> part of the CF standard document, I wonder?
>
> Cheers
>
> Jonathan
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
Bryan Lawrence
Director of Environmental Archival and Associated Research
(NCAS/British Atmospheric Data Centre and NCEO/NERC NEODC)
STFC, Rutherford Appleton Laboratory
Phone +44 1235 445012; Fax ... 5848;
Web: home.badc.rl.ac.uk/lawrence
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Received on Tue Jan 11 2011 - 05:28:54 GMT
