Re: [cf-satellite] Query related to CF conventions

On Jul 29, 2011, at 2:07 PM, John Caron wrote:

> On 7/29/2011 11:31 AM, Lynnes, Christopher S. (GSFC-6102) wrote:
>> On Jul 29, 2011, at 8:40 AM, John Caron wrote:
>> 
>>> 2. CF uses netCDF as its file format.
>> John,
>>   How true is this statement?  Our own Global Modeling and Assimilation 
>> Office claims to be making CF-compliant HDF4 data, and Russ Rew has the 
>> following statement in the RFC about CF that he submitted to the NASA SPG:
>> 
>> "Because of its simplicity and generality, other file formats can be modeled 
>> using the CF data model. Thus the concepts and relationships specified in CF 
>> may be applied to other formats by mapping the variable, dimension, and 
>> attribute abstractions in the CF data model to analogous concepts in the 
>> other formats, in a way that preserves the essential characteristics of the 
>> data model needed by the CF conventions."
>> 
>> Are we just kidding ourselves if we say we have HDF4 data that is 
>> CF-compliant?
>> --
>> 
> 
> Hi Chris:
> 
> Well, I agree with Russ that "other file formats can be modeled", and 
> its not particularly hard. To make an HDF4/CF mapping robust, you should 
> start a public document that clarifies any issues between the netcdf and 
> hdf4 data model that affects CF. One that I know about is the lack of 
> shared dimensions in HDF4. HDF-EOS got around it in their ODL. One could 
> also use dimension scales (is that what you are doing?), although there 
> may be some things to clarify there. There are likely a cases to 
> document. The issue that Ghansham brought up might be another one.
> 
> So id say you arent fooling yourself exactly, but you may not be 
> interoperable with CF-reading software. A public web page that we can 
> link to from our conventions page would likely be the ticket.
> 
> John

Hmmm...OK, food for thought.  I have occasionally argued that someone should 
define what it mean to implement CF in HDF4, but don't want to stick my head 
above the parapet again at this particular time...
--
Dr. Christopher Lynnes     NASA/GSFC, Code 610.2    phone: 301-614-5185