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Status of updated version of DDLm core cif

  • To: Distribution list of the IUCr COMCIFS Core Dictionary Maintenance Group <coredmg@iucr.org>
  • Subject: Status of updated version of DDLm core cif
  • From: James Hester <jamesrhester@gmail.com>
  • Date: Mon, 27 Jun 2016 13:53:47 +1000
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Dear Core Dictionary Maintenance Group,

The 6-week review of the DDLm version of the core dictionary has ended.  However, serious discussion is continuing in the DDLm group (see messages following from http://www.iucr.org/__data/iucr/lists/ddlm-group/msg01428.html and subsequent threads) around a way to allow looping of ordinarily single-valued datanames.  That discussion arose from a need to resolve the schizophrenic nature of the symmetry dictionary datanames: they are loopable, but are aliased to the old 'unloopable' symmetry datanames, and are indeed almost exclusively assumed to be unlooped in current software; for more details see that discussion thread. 

While undesirable, it is just possible that, as a result of these discussions, the DDLm core dictionary may need some minor changes. If any changes involve a changed dataname or interpretation of a dataname, the changed portions will be presented here for your review.

In any case, I will hold off passing the DDLm core_cif dictionary to COMCIFS for final approval until the discussions in the DDLm group have been resolved, so I continue to invite any further comments that you have on the current version.

best wishes,
James Hester
Acting Core DMG chair

On 13 May 2016 at 12:22, James Hester <jamesrhester@gmail.com> wrote:
Dear Core CIF DMG members,

I have completed merging the symmetry dictionary into the draft DDLm core CIF dictionary with advice from David Brown. To avoid cluttering your mailboxes with 1M files, the link to the latest version is:


Unfortunately there are too many changes for the Github automated 'diff' listing of the changes to be provided. The important changes can all be found following the 'SPACE GROUP' category, and see my notes below.

A new 6-week review period starts today.  As before, please check those areas of the dictionary that time and your expertise permit, and start a new mail thread for each distinct topic to help manage the conversation. Even if you find no issues, a public message that you have conducted a review and are satisfied is better than silence.

James Hester (acting Core DMG chair).

Notes on the symmetry dictionary merging:

(1) Categories 'symmetry' and 'symmetry_equiv' have been changed to 'space_group' and 'space_group_symop' respectively, in line with the names used in the symmetry, modulated structures, and forthcoming magnetic dictionaries.
(1.1) Where the part of the name following the category name differs, the symmetry dictionary version was chosen.
(2) Category 'space_group_Wyckoff' has been transferred across from the symmetry dictionary
(3) New category 'space_group_generator' has been created as the space group generators should not be looped together with the symmetry operators.
(4) Category 'space_group' is now not loopable, that is, only a single space group can be provided in any data block (as was the case for the 'symmetry' category). If this wrecks your use case, please start a conversation.
(4.1) Any datanames used to identify a particular space group from the loop of space groups have therefore been dropped as they are now unnecessary
(5) Datanames from the symmetry dictionary linked to the reference setting have not been merged as, to be useful, they would require new datanames for every affected concept e.g. atom_site.pos_x_reference, refln.hkl_reference. These would only clutter up the core dictionary but might be usefully defined in a reborn symmetry dictionary if anyone wants to volunteer.

T +61 (02) 9717 9907
F +61 (02) 9717 3145
M +61 (04) 0249 4148

T +61 (02) 9717 9907
F +61 (02) 9717 3145
M +61 (04) 0249 4148
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