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Re: proposal for valence items



Dear David,

  Thank you for your ingenious idea of putting the chirality definition
into CIF form. I must confess that in setting down one example I rather
feared that you would be able to find some specific trick for squeezing
it into CIF format.

   Even as a specific example, I do not find it satisfactory as it
attributes possible data values of 'yes' or'no' to a text definition.
This is just what I wish to avoid.

> I don't know what other items you want to define, so I can't
> comment on whether the same trick would work for them.

   I could tell you all about the ones that I already need but there
will always be others in the pipe line presenting new difficulties if we
adopt the 'trick' technology. To a user hunting for data terms in the
CIF dictionnary, it will be far from obvious which data values are the
ones that are intended for real use, and which are those present as a
trick to allow a dictionnary definition. 

> Is it worth
> thinking again about adding these definitions?

  As I understand things today, I am not in favour of following your
approach.

Best wishes,
  Howard

-- 
Howard Flack        http://www.unige.ch/crystal/ahdf/Howard.Flack.html
Laboratoire de Cristallographie               Phone: 41 (22) 702 62 49
24 quai Ernest-Ansermet             mailto:Howard.Flack@cryst.unige.ch
CH-1211 Geneva 4, Switzerland                   Fax: 41 (22) 702 61 08

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