Dear Martin,
This sounds an excellent idea. What do you thinks of the idea of building the knowledge into NVS to make it accessible in machine-readable form and so the requirements could be enforced by the CF checker?
Cheers, Roy.
-----Original Message-----
From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of martin.juckes at stfc.ac.uk
Sent: 07 July 2016 12:01
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Recording requirements expressed in standard name definitions
Dear All,
in connection with ticket 151 (
http://cf-trac.llnl.gov/trac/ticket/151) I had proposed a section in appendix B listing standard names whose definitions impose additional constraints on variable attributes etc. Jonathan convinced me that ticket 151 was not the right place for this.
The proposal for this new section was motivated by the fact that standard name descriptions cannot include examples or markup, and the specification of the rules is not as clear as in the convention text. It also appears that the rules are not checked by the CF checker (at least not the few that I have looked at in detail) and I think the best way to get consistent checking would be to first create a well structured summary of these rules in the conventions document.
The constraint related to ticket 151 is that variables with standard name "region" or "area_type" must be consistent with the standard region and area type lists.
I have reviewed the first half of the standard name list (a to m) and found the following coordinate constraints expressed:
(1) area_fraction: requires an area_type coordinate;
(2) atmosphere_lifting_condensation_level + 2 others: requires an original_air_pressure_of_lifted_parcel coordinate.
(3) Many "layer" quantities (e.g. dry_static_energy_content_of_atmosphere_layer): require vertical coordinate with bounds.
(4) change_in_energy_content_of_atmosphere_layer_due_to_change_in_sigma_coordinate_wrt_surface_pressure: must have a vertical coordinate variable (axis=Z)
(5) change_over_time_... and .._displacement: require bounds on time coordinate
(6) downwelling_photosynthetic_photon_radiance_in_sea_water and other radiance variables: direction must be specified, e.g. with coordinate of "zenith_angle".
(7) mass_concentration_of_pm..._ambient_aerosol_in_air (and mass_fraction_of_pm..): require air_temperature and relative_humidity
(8) isotropic_radiance_per_unit_wavelength_in_air (and other per_unit_wavelength varables): the definition is slightly ambiguous with the sentence "A coordinate variable for radiation wavelength should be given the standard name radiation_wavelength" which, taken literally, means the use of a wavelength coordinate is optional: should it be "A coordinate variable for radiation wavelength should be given with the standard name radiation_wavelength", making the wavelength coordinate required?
Is it worth completing the review of the standard name desriptions and creating an appendix section to list these constraints, giving examples (or pointing to examples which may be better positioned in relevant portions of the main text)?
regards,
Martin
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Received on Wed Jul 13 2016 - 02:38:04 BST
