Variants
James Hester
jamesrhester at gmail.com
Thu Nov 26 05:36:56 GMT 2009
I include David's original message below for reference.
---------------------------
(from David Brown)
Dear Colleagues,
Last September I circulated for fast track approvel a recommendation for
adding a new item:
_diffrn_radiation_wavelength_nominal,
to the core dictionary (see below for details). The intent was that this
could be used for giving a nominal wavelength calculated e.g., from the
paparmeters of a diffractometer. It was proposed tht this might be needed
for completeness even though it was not accurate enough for calculating
lattice parameters, etc. This proposal was passed by the core CIR
dictionary maintenance group by default (no one raised any objection). When
this proposal was subsequently presented for final approval to COMCIFS, Nick
Spadaccini suggested a more elegant alternative, namely that by adding
instead the item
_diffrn_radiation_wavelength_determination
we could loop the nomiinal wavelength with the refined (and any other
interesting) wavelengths. This would be more informative and allow for
future expansion.
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
According to our rules, this proposal is being posted for comment to the
coreCIF dictionary maintenance group for the next six weeks. At the end of
this time, if there are no unresolved issues, the core dictionary
maintenance group will be deemed to have accepted the proposal.
David Brown
==============================================================
The proposal is to add the following item to the coreCIF dictionary:
=============================================
2009-09-25 Proposal from the Nick Spadaccini on the COMCIFS dicsussion list
to replace a withdrawn proposal.
data_diffrn_radiation_wavelength_determination
_name '_diffrn_radiation_wavelength_determination'
_category diffrn_radiation_wavelength
_type char
_list both
_list_reference '_diffrn_radiation_wavelength_id'
loop_
_enumeration
_enumeration_detail
'fundamental'
'Wavelength that is a fundamental property of matter e.g. MoK\alpha'
'estimated'
'Estimated from secondary information e.g. monochromator angle or
time of flight'
'refined'
'Based on refinement using a standard material with known cell
parameters'
_definition
; The method of determination of incident wavelength. Further
information may be provided in _diffrn_radiation_special_details
;
On Thu, Nov 26, 2009 at 1:14 PM, Herbert J. Bernstein <
yaya at bernstein-plus-sons.com> wrote:
> You removed David's original message from mine. Please add that to
> the thread as well.
>
>
> =====================================================
> Herbert J. Bernstein, Professor of Computer Science
> Dowling College, Kramer Science Center, KSC 121
> Idle Hour Blvd, Oakdale, NY, 11769
>
> +1-631-244-3035
> yaya at dowling.edu
> =====================================================
>
> On Thu, 26 Nov 2009, James Hester wrote:
>
> 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
>> yaya at dowling.edu
>> =====================================================
>>
>>
>>
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