Russ and all,
One aspect of netCDF-4 we almost certainly expect to make use of for
CMIP6 is the "automated" compression option. As far as I know, this
does not affect the conventions. If you see a problem with this, please
let me know right away.
Karl
lem any
On 9/10/14, 9:16 AM, Russ Rew wrote:
> Jim,
>
> I'm hoping more data providers follow your approach, as it will
> gradually bring along software developers, other data providers, and
> ultimately conventions authors. I gave a talk
> <http://www.unidata.ucar.edu/presentations/Rew/agu_2010_nc4_Rew.pdf>
> at AGU a few years back about how to manage the transition to the
> netCDF-4 enhanced data model. The obstacles to the transition are
> summarized in slides 19-21, where my lack of artistic talent is
> demonstrated in an illustration of the "chicken and egg logjam".
>
> --Russ
>
>
> On Wed, Sep 10, 2014 at 9:25 AM, Jim Biard <jbiard at cicsnc.org
> <mailto:jbiard at cicsnc.org>> wrote:
>
> Tim,
>
> You can use netCDF-4 without "classic" format, but for true, full
> CF compliance you can't use any new features.
>
> Personal opinion alert!!! The following is just my personal
> opinion. I'm not trying to stir up trouble. I'm just sharing my
> observations on my experiences. Please don't hate me.
>
> The official CF community position is that for
> backwards-compatibility reasons, they would rather not adopt new
> features unless there is no "good" workaround using the old
> feature set. Contention can arise over the question of whether you
> view the workaround as "good" or not, but that seems to be roughly
> how the thought goes. The CF community also do not view themselves
> as developers of new features that aren't driven by present needs.
> They are also interested in maximizing the ability of (sometimes
> theoretical) existing CF-aware analysis packages to properly
> handle all CF-compliant files.
>
> In previous conversations I've been given to understand that the
> effective process for bringing new netCDF features into CF will be
> for someone to use them in a dataset, doing their best to
> interpret CF in the light of the new features. If it is a popular
> dataset, it will push the CF community towards adopting some form
> of those new features.
>
> In a case where I was developing a new dataset that would have
> been particularly unwieldy (in my opinion) without groups, I went
> ahead and used them, applying a hierarchical scope approach to
> file and group attributes. As my dataset is not likely to be
> widely used by any analysis packages, it will not likely cause
> anyone grief or drive the adoption of new netCDF features into CF.
>
> Grace and peace,
>
> Jim
>
>
> On 9/10/14, 9:53 AM, Timothy Patterson wrote:
>> Is it correct to say that, although they don't explicitly state it, the CF conventions (1.6 and the draft 1.7) restrict compliant netCDF products to be either netCDF-3 or netCDF-4 in classic format? There are no conventions for the enhanced features such as groups and user-defined types like enumerated variables, and Section 2.2, as an example, bars the use of unsigned integer variables or string variables (which are even stated not to exist, again implying classic-model only).
>>
>> There are some features of the enhanced model we want to use for our future datasets (such as groups) and some features which would make life easier but could be worked around if it led to CF compliance (enumerated types, unsigned integers, string types, etc.). Are there any plans to introduce conventions for the use of these enhanced features at some point in the future or would non-classic model datasets always be seen as non-compliant?
>>
>> Thanks for your insights on this issue!
>>
>> Regards,
>>
>> Tim Patterson
>>
>>
>>
>> ---------------------
>>
>> Dr. Timothy Patterson
>> Instrument Data Simulation
>> Product Format Specification
>>
>> EUMETSAT, Eumetsatallee 1, D-64295 Darmstadt, Germany
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