[CF-metadata] New standard name: datetime_iso8601 [John Graybeal et al.]

From: Schultz, Martin <m.schultz>
Date: Wed, 20 Mar 2013 08:09:59 +0000

Dear all,

     interesting discussion. From the point of view of an outsider (not dealing with ocean data ;-) there are two issues which still aren't entirely clear to me:

1) as Steve Hankin wrote, this variable has a potential to deflect from the actual physical quantity, which is expressed in the "time" dimension variable. This is no harm as such, but I am wondering if we shouldn't make this relation clearer, for example by defining the standard_name as "time_expressed_as_iso8601", or perhaps more precisely "datetime_expressed_as_iso8601". (Yes, Jonathan, I can see that this could open a backdoor towards replacing the numerical time construct by a string variable eventually...).

2) I agree with a few others that human readability should not be a criterion as such. If you think this through, then we would have to go back to ascii for everything (then I will look for a new job). I do, however, appreciate the need for documenting, i.e. preserving original datetime labels as they may have been sent for example from buoys. But in this sense, this variable only serves as a label and could in principle be some different entity such as a UUID or a random number. This has a very important consequence, because it implies that this datetime information should never be used by any software for processing (date)time information.

I hope you have detected that 1 and 2 are almost orthogonal to each other. I have a feeling that you lean towards 2 with your standard_name proposal, but that you have a secret wish to actually use datetime_iso8601 as a "real" time variable. This makes me slightly worried, unless there is a formal discussion to extend the convention via a track ticket.

Another issue is the default time zone. I couldn't quite follow whether the default will be "local" or "UT" in the end. If "UT" which makes a lot more sense in terms of "CF interoperability", this would break the ISO standard. This can of course be overcome by a community profile, but then there should also be a clear reference to this standard (a namespace attribute?).

Best regards,

Martin



PD Dr. Martin G. Schultz
IEK-8, Forschungszentrum J?lich
D-52425 J?lich
Ph: +49 2461 61 2831




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Received on Wed Mar 20 2013 - 02:09:59 GMT