Hi Steve
> A high
> level description of the CF data model (pinning down concepts
> intuitively for readers as well as formal UML) would be a valuable
> addition to the document. (Maybe make this a trac ticket?)
Agreed: we need both ...
> Bryan -- I'd like to make sure that the vocabulary is clear in
> interpreting your words. "NetCDF" is an ambiguous term in this
> context, because it is both a data model and a file format. I see
> the CF data model as a specialization of the netCDF data model,
> rather that a roll-your-own from scratch. To borrow the
> terminology from the de jure world, I see the netCDF-3 data model as
> a normative standard for CF. From a standard pov CF is stronger
> because it builds upon the netCDF data model. From your UML I
> infer that you are seeing things the same way. (It was the words
> that seemed ambiguous.)
Clearly the existing CF definition builds from NetCDF, logically from the
NetCDF data model ... as you say, that's the way it is, so that's the
way I modelled it. Clearly the implementation is wrt the NetCDF data
format. As Russ points out in his email, the extension to other formats
could simply involve making sure one can implement the NetCDF parts of
the data model in those formats ...
It might be that with some slight tweaking of a *future* version of CF,
expressed only as a data model, we can further simplify the
implementation of CF in other formats. It may be that such
simplilfication is unnecessary. Where it becomes interesting is when
someone wants to consider using aspects of the netcdf4 data model
directly within CF. Ideally we separate the efficient implementation from
the underlying data model, but pragmatism usually requires a compromise.
> What seems a significant omission in this discussion, though, is the
> coupling to the CDM, which has already traversed much of this formal
> data modeling terrain. There is much to be gained in merging the
> two bodies of work. (And much to be lost by diverging.) This
> effort seems like the opportunity to pin down the areas where there
> is currently divergence.
I think we start with what we have, agree on a precise description of
that, then we evolve. I suspect we should see the CDM as a profile of CF
... (perhaps for our community, *the* profile, but for me, that would
depend on the complete convergence of the logical properties of CSML and
CDM).
Cheers
Bryan
--
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
Received on Wed Jan 12 2011 - 02:02:45 GMT
