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update



Dear Colleagues,

	It is time for a brief update on developments in the review of the
cif_core dictionary over the summer.

	The items already accepted by the Dictionary Maintenance Group
(DMG) were sent to COMCIFS for formal acceptance.  COMCIFS queried some
items and these were referred back to the DMG for further consideration.
The other items were all accepted in time to make the deadline for
International Tables vol. G which will describe the CIF project as it is
at the moment.  The new version, cif_core_2.3, has been approved and will
shortly be posted on the IUCr web site.

	There was an informal meeting of the people formulating items for
TWINNING at the ACA meeting in Cincinnati.  The names of some items have
been proposed, but there are still some conceptual problems related to the
labelling of reflections that need to be worked out.  Victor Young is
leading this group.

	One of the items that was referred back to the DMG concerned the
definition of Z'.  It was pointed out that we cannot define Z' until we
have defined the molecule to which it refers.  This drew attention to the
fact that CIF currently defines many crystallographic items, but very few
chemical items (properties of atoms, bonds, molecules, complexes etc.)
Adding these items is not a trivial exercise since they will need their
own categories with links to the existing crystallographic items, so I am
assembling a small group to look at the problem.  I will be instructing
them to report back to the DMG with suggesions that we can consider.

	This still leaves a number of items for us to work on while we
wait for the other groups to report, and I will be circulating another
list of suggested revisions shortly so that we can continue to work
towards version 2.4.

				David
				Chair of the core DMG


*****************************************************
Dr.I.David Brown,  Professor Emeritus
Brockhouse Institute for Materials Research,
McMaster University, Hamilton, Ontario, Canada
Tel: 1-(905)-525-9140 ext 24710
Fax: 1-(905)-521-2773
idbrown@mcmaster.ca
*****************************************************


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