On 3/25/2013 10:40 AM, Jonathan Gregory wrote:
Dear Ken
Thanks for your response too (copied here? is it bad form in a listserv to
consolidate responses like this?)
I think it's convenient, myself!
That answer seems so easy and obvious that I wonder if I asked the question
properly! I'll have to ask Tim to be sure, but I think the standard deviation
is the standard deviation over time, of means generated in each time-area-depth
cell.
But I think the question still remains about being able to use a standard name, which we
would like to do of course? I am pretty sure in this example for this standard deviation
variable we should NOT use sea_water_temperature for standard_name, and that it would be
good if there were more standard name modifiers to choose from. If there were, perhaps
we could set standard name to something like "sea_water_temperature
standard_deviation".
You *should* use sea_water_temperature as the standard_name. The standard_name
alone is not to be regarded as the description of the metadata. It has to be
taken in combination with cell_methods and modifiers. Maybe it seems more
surprising that a temporal standard deviation of sea_water_temperature has
sea_water_temperature for its standard name, but it's really the same kind of
idea - i.e. a statistic - as a temporal mean or a temporal maximum, isn't it.
Even if it was variance its standard_name would be sea_water_temperature, and
in that case the units would be different too.
Hi Jonathan,
What you have just described is the state of CF standard_name today.
But elements of it remain problematic. What do you see as the *purpose*
of CF standard_names? What are the use cases by which standard_names
will lead to better interoperability?
One use case that we are already seeing is that standard_name attributes
are harvested from CF files and used in search engines. If a variable
named as sea_water_temperature in a file is really
time_variance_of_sea_water_temperature, because of its cell_methods,
then we need to be pro-active in making sure that the search engines
harvest the information found in cell_methods, too. This level of
sophistication has not yet emerged into the ISO metadata world. I'm
concerned that if we invoke sophisticated ISO machinery(*) to solve the
problem, we may have a solution in name only -- will this level of
complexity have a hope of becoming widely enough used to bring
interoperability?
- Steve
* Our colleague Dave Neufeld at NOAA/NGDC has pointed out that the ISO
"lineage" model may address the semantics of cell_methods --
https://geo-ide.noaa.gov/wiki/index.php?title=ISO_Lineage.
Cheers
Jonathan
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