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Re: Variants

David Brown wrote:
...
> Is a CIF a fixed archive, a place 
> where we entomb a fact of nature, or is it an evolving document that 
> carries it own history along with it?

CIF is becoming the standard data format for working crystallography 
experiments, not just an archival format. Maybe the goal should be that 
_variant components can be removed from archival CIFs, in a way that 
does not complicate non-variant data.

To me, the _diffrn_radiation_wavelength_determinaton approach is 
confusing. The wavelength id is defined mainly for multiple wavelength 
experiments. Using _variant, multiple wavelengths might be defined like 
this:

          loop_
              _diffrn_radiation_wavelength_id
              _diffrn_radiation_wavelength_variant
              _diffrn_radiation_wavelength
                 1   final   1.23456
                 1   prelim   1.25
                 2   final   1.00


Some suggestions:

Maybe use "_variant_id" instead of "_variant_variant"?

Maybe the _variant_* items should include an identifier as to what 
primary value is being varied, when one exists. In this case, the 
wavelength value is the primary varying value, and all others are derived.

Thanks,
Joe Krahn

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