All Steve's questions seem good to me. The last paragraph, about just
being a "basis for their community standard", raises another: Is that
the model CF intends to follow?
My assumption, having understood that CF wants to be capable of
representing observational data, was that CF would want to go 'all the
way', and be capable of representing any of the observational data
that the community collects and exchanges for oceanographic science
reasons. This can include strange new concepts, many raw (not yet in
science units, or not yet calibrated) data items, and diagnostic and
engineering data.
Steve's cited examples perhaps reflect the distance that has to be
covered. In our research environment, CF standard_names are only
occasionally applicable to the collected raw data.
So I'm hoping the question of intended CF scope is answered, or at
least addressed, in the course of resolving this specific instance.
john
On Oct 27, 2008, at 8:44 AM, Steve Hankin wrote:
> Hi all,
>
> Please forgive me for butting in late in a discussion. As an
> listener, but not a participant, I find that I am not clear on the
> ground rules for making decisions. Should CF standard names convey:
> how a measurement was made?
> for what purpose a parameter was measured?
> Underlying this discussion is a discomfort with the notion that
> there could be more than one variable in a CF file bearing the
> standard_name "time". Is this a valid discomfort?
>
> I'd note that observation communities such as OceanSites, Argo and
> GOSUD that have adopted CF have regarded CF only as the basis for
> their community standard. CF is not presumed to be sufficient as-
> is. They have extended CF with many additional attributes and
> variables that convey the subtler levels of semantics their
> community requires to capture all of the details of a measurement
> type.
>
> - Steve
>
> P.S. Regarding the question below -- "which is the true time?" --
> can this be addressed through the use of the CF "coordinate = "
> attribute?
>
> ================================================================
>
> Jonathan Gregory wrote:
>>
>> Dear John
>>
>>
>>> Uh, to an observing systems/cyberinfrastructure person, ALL time
>>> values have errors, _especially_ those from devices.
>>>
>> I think the point is, as Nan says, that the data user will want
>> there to be one
>> "time" which is to be regarded as coordinated, as the "true" time,
>> in the sense
>> that data values with the same coordinate of time are to be
>> regarded as truly
>> simultaneous. It is up to the data-writer to provide this
>> coordinate if
>> possible as they are typically better able to do it than the user.
>> This one has
>> the standard_name of "time".
>>
>> Regarding time_from_device, I would say that is not clear to me,
>> because *all*
>> times come from some device, even if it is an atomic clock
>> determining the UTC
>> standard! What about time_from_instrument. Would that be clearer
>> than sensor?
>> I think a sensor is a sampler in the existing name
>> temperature_of_sensor_for_oxygen_in_sea_water
>> but perhaps Nan or Roy could comment.
>>
>>
>>> mission_elapsed_time is fine.
>>>
>> OK.
>>
>> My point about redundancy refers particularly to the time within
>> year and day.
>> Do you mean the device is giving you both the time (elapsed since
>> some
>> reference) and its components (time within year and day etc.). The
>> time and
>> its components are related by well-defined arithmetic. Do you want
>> to record
>> them all separately? If so, why? Perhaps for completeness, to be on
>> the safe
>> side?
>>
>> Thanks for the discussion. Best wishes
>>
>> Jonathan
>> _______________________________________________
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>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
>
> --
> Steve Hankin, NOAA/PMEL -- Steven.C.Hankin at noaa.gov
> 7600 Sand Point Way NE, Seattle, WA 98115-0070
> ph. (206) 526-6080, FAX (206) 526-6744
>
> "The only thing necessary for the triumph of evil is for good men
> to do nothing." -- Edmund Burke
> _______________________________________________
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John
--------------
John Graybeal <mailto:graybeal at mbari.org> -- 831-775-1956
Monterey Bay Aquarium Research Institute
Marine Metadata Interoperability Project:
http://marinemetadata.org
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