New CIF dictionaries
The last report from the committee appointed by the IUCr to oversee the CIF project, Comcifs, described the current status of the core (coreCIF), powder diffraction (pdCIF) and macromolecular (mmCIF) dictionaries, and gave details of the three dictionary maintenance groups that have been established to continue their development (IUCr Newsletter Vol. 6 No.4 page 6).
New specialized CIF dictionaries to cover branches of crystallography not covered are being prepared. Once provisional approval has been given, the draft dictionaries will be made available on the web for public input. Final approval of the dictionary usually occurs after potential users have had a chance to comment and suggest changes. Below is a summary of the current state of the dictionaries under development. Anyone interested in contributing to them should contact the project leader.
MODULATED STRUCTURES (msCIF.dictionary) Project leader: G. Madariaga (email@example.com) This dictionary will provide the data items needed to give a complete description of modulated structures. It is in an advanced state of preparation and will shortly be presented to Comcifs for provisional approval.
IMAGES AND HIGHER DIMENSIONAL DATA (imgCIF/CBF) Project leader: A. Hammersley (firstname.lastname@example.org) The purpose of this dictionary is image storage. Initially the focus is on 2-D image data-sets, but the dictionary will be flexible enough to allow storage of multi-dimensional data-sets. To encode the large amount of information needed to define an image in a way that made reading and writing the file efficient, the group decided that the image had to be written in binary. Unfortunately, this contravenes the basic premise that all cifs are written in ASCII. Consequently, a CBF (Crystallographic Binary File) will be used for file transfers between computers, while the fully cif compliant imgCIF written in ASCII will be used for archiving. Both files use identical data names and definitions and have the same structure. The only difference is that CBFs are written as binary files and imgCIFs are written as ASCII files. H. Bernstein and P. Ellis have been working on software that will convert one into the other. This dictionary will be coming to Comcifs for tentative approval within the next few months.
SYMMETRY (symCIF.dictionary) Project leader: D. Brown (email@example.com) The purpose of this dictionary is to define all the symmetry items that are needed to describe the contents of International Tables Vol A and to provide a framework in which, for example, tables of sub- and super-groups can be expressed.
DIFFUSE SCATTERING (dsCIF.dictionary) Project leader: T. Proffen (firstname.lastname@example.org) Currently identifying the concepts needed in a diffuse scattering dictionary.
ELECTRON DENSITY (rhoCIF.dictionary) Project leader: P. Mallinson (email@example.com) This dictionary will provide the data items needed for reporting the results of electron density studies.
SMALL ANGLE SCATTERING (sasCIF.dictionary) Project leader: M. Malfois (firstname.lastname@example.org) A draft dictionary describing the items needed in the small angle scattering field.
MAGNETIC STRUCTURES (magCIF.dictionary) Project leader: W. Sikora (email@example.com) This dictionary is being developed in conjunction with the establishment of an electronic version of the Database of Magnetic Structures Determined by Neutron Diffraction in Krakow.
The CIF dictionaries are copyrighted by the IUCr in order to protect the CIF standard. Any file that calls itself a CIF must comply with the standard laid down in these dictionaries. Anyone interested in expanding CIF into areas not covered, should contact the chair of Comcifs, D. Brown (firstname.lastname@example.org) or the secretary (B. McMahon, email@example.com).