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Variants

  • To: "Discussion list of the IUCr Committee for the Maintenance of the CIFStandard (COMCIFS)" <[email protected]>
  • Subject: Variants
  • From: James Hester <[email protected]>
  • Date: Thu, 26 Nov 2009 10:59:19 +1100
I'm reposting Herbert's message in a new thread to aid organisation.� Herbert wrote:

----
Dear Colleagues,

�While you are revisiting this item, I would suggest you consider the more complete (and, I believe, more elegant and general) solution of defining "variants", that we have introduced into the imgCIF dictionary to handled quantities that may be determined in different ways.

�Instead of adding

�_diffrn_radiation_wavelength_
determination

you would add

�_diffrn_radiation_wavelength_variant

and a new variant category


� � � �_variant_variant
� � � �_variant_role
� � � �_variant_timestamp
� � � �_variant_variant_of
� � � �_variant_details

which would allow you with complete generality to manage any number
a refined or redefined quantities, such as wavelengths. �This would
then allow you to us the same variant identifier, for, say cell
dimensions, which could be expected to change in a coupled manner
with the changes in wavelength.

�If you are interested in this more complete approach, I can provide
you with the full item definitions, but the short form is:

� � � �_variant_variant


� � � � � � �The value of _variant_variant must uniquely identify
� � � � � � �each variant for the given diffraction experiment and/or
� � � � � � �entry

� � � �_variant_role

� � � � � � �The value of _variant_role �specifies a role

� � � � � � �for this variant. �Possible roles are null, "preferred",
� � � � � � �"raw data", and "unsuccessful trial".

� � � �_variant_timestamp


� � � � � � �The date and time identifying a variant. �This is not
� � � � � � �necessarily the precise time of the measurement or
� � � � � � �calculation of the individual related data items, but a timestamp that
� � � � � � �reflects the order in which the variants were defined.

� � � �_variant_variant_of


� � � � � � �The value of _variant.variant_of gives the variant
� � � � � � �from which this variant was derived. �If this value is not
� � � � � � �given, the variant is assumed to be derived from the default
� � � � � � �null variant.

� � � �_variant_details


� � � � � � �A description of special aspects of the variant


An example of how this might be used is:

� � � � loop_
� � � � � � _diffrn_radiation_wavelength_id
� � � � � � _diffrn_radiation_wavelength
� � � � � � _diffrn_radiation_wavelength_determinaton
� � � � � � � �1 � 1.23456 � fundamental
� � � � � � � �2 � 1.25 � � �estimated


would become

� � � � �loop_
� � � � � � �_diffrn_radiation_wavelength_variant
� � � � � � �_diffrn_radiation_wavelength
� � � � � � � � final � 1.23456
� � � � � � � � pelim � 1.25

� � � � �loop_
� � � � � � �_variant_variant
� � � � � � �_variant_role
� � � � � � �_variant_timestamp
� � � � � � �_variant_variant_of
� � � � � � �_variant_details
� � � � � � �final preferred 2007-08-04T01:17:28 prelim refined
� � � � � � �prelim . � � � �2007-08-03T23:20:00 . .

� � � � �loop_
� � � � � � _cell_variant
� � � � � � _cell_length_a
� � � � � � _cell_length_b
� � � � � � _cell_length_c
� � � � � � _cell_angle_alpha
� � � � � � _cell_angle_beta
� � � � � � _cell_angle_gamma
� � � � � � final �22.5 22.5 22.5 90. 90. 90.
� � � � � � prelim 22.3 22.3 22.3 90. 90. 90.


�Regards,
� �Herbert


=====================================================
�Herbert J. Bernstein, Professor of Computer Science
� Dowling College, Kramer Science Center, KSC 121
� � � �Idle Hour Blvd, Oakdale, NY, 11769

� � � � � � � � +1-631-244-3035
� � � � � � � � [email protected]
=====================================================


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