The Commission conducted its work during the triennium either by letter or by fax, being able to make use of electronic mail only during the first and last days of the period. Membership of the Commission increased sharply following the Bordeaux General Assembly. All members are ex officio appointments as Editors of the IUCr journals, each volume of the International Tables for Crystallography and Structure Reports. In addition, the Chairs of the IUCr/OUP Book Series Committee and the Commission on Crystallographic Teaching are new appointments, resulting in a total strength of 11 members. Its principal activities have been carried out, as has been customary, by its Committees, Sub-committees and Working Groups.
The final Report of the IUCr ad hoc Committee on the Nomenclature of Symmetry, under the Chairmanship of P. M. de Wolff, was published in Acta Cryst. (1992), A48, 727-732. In addition to redefining printed symbols for symmetry elements, the Report recommends use of the letters e and k for certain glide planes that previously were without either a unique or a specific symbol.
The Sub-committee on the Nomenclature of N-Dimensional Crystallography, under the Chairmanship of A. J. C. Wilson and with membership as given in Acta Cryst. (1991), A47, 611, set up a Working Group with the limited task of comparing and evaluating the existing nomenclatures of crystal families, crystal systems and Bravais lattices in four dimensions followed by the presentation of a recommended nomenclature. The first task was completed early in the triennium. The Working Group, however, has not found it possible to resolve the differences between several widely divergent naming and notation proposals. Accordingly, the Commission is considering a temporary suspension of activity in this nomenclature area to allow fresh thought to develop in this growing crystallographic field.
A Working Group of the Commission, consisting of the Editors (V. Kopsky and D. B. Litvin) of Volume E of International Tables for Crystallography, has completed a Report entitled Nomenclature, Symbols and Classification of the Subperiodic Groups. The Commission accepted the final Report, which will be published in Volume E in due course, and agreed that an Abstract of the Report should be published in Acta Cryst. as a form of advance notice to the crystallographic community. Preprints of the Report are available from D. B. Litvin. The Report recommends symbols for the seven frieze groups, 80 rod groups, and 75 layer groups together with symmetry tables and a classification of the subperiodic groups.
The Commission is considering the establishment of a Working Group to examine the recently issued ISO Guide to the Expression of Uncertainty in Measurement for its possible impact on the nomenclature of statistical techniques used in crystallography and to be charged with making such recommendations as are appropriate.
15 February 1993 S. C. ABRAHAMS, Chairman
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