Tables for
Volume G
Definition and exchange of crystallographic data
Edited by S. R. Hall and B. McMahon

International Tables for Crystallography (2006). Vol. G, ch. 2.2, p. 33

Section Name space

S. R. Hall,a* N. Spadaccini,c I. D. Brown,d H. J. Bernstein,e J. D. Westbrookb and B. McMahonf Name space

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(9) The intention of the maintainers of public CIF dictionaries is to formulate a single authoritative set of data names for each CIF dialect (i.e. DDL1 and DDL2), thus facilitating the reliable archive and interchange of crystallographic data. However, it is also permissible for users to introduce local data names into a CIF. Two mechanisms exist to reduce the danger of collision of data names that are not incorporated into public dictionaries.

(10) The character string [local] (including the literal bracket characters) is reserved for local use. That is, no public dictionary will define a data name that includes this string. This allows experimentation with data items in a strictly local context, i.e. in cases where the CIF is not intended for interchange with any other user.

(11) Where CIFs including local data items are expected to enjoy a public circulation, authors may register a reserved prefix for their sole use. The registry is available on the web at .

A reserved prefix, e.g. foo, must be used in the following ways:

(i) If the data file contains items defined in a DDL1 dictionary, the local data names assigned under the reserved prefix must contain it as their first component, e.g. _foo_atom_site_my_item.

(ii) If the data file contains items defined in a DDL2 dictionary, then the reserved prefix must be:

  • (a) the first component of data names in a category defined for local use, e.g. _foo_my_category.my_item.

  • (b) the first component following the period character in a data name describing a new item in a category already defined in a public dictionary, e.g. _atom_site.foo_ my_item.

(12) There is no syntactic property identifying such a reserved prefix, so that software validating or otherwise handling such local data names must scan the entire registry and match registered prefixes against the indicated components of data names. Note that reserved prefixes may not themselves contain underscore characters.

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