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. 3.1, pp. 86-87

Section The dictionary register

B. McMahona*

aInternational Union of Crystallography, 5 Abbey Square, Chester CH1 2HU, England
Correspondence e-mail: The dictionary register

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COMCIFS maintains a register of dictionaries known to it, including the identifying name and version strings within those dictionaries. The register also includes the location of each dictionary, expressed at present as a URL designed to allow retrieval by file transfer protocol (ftp) from the IUCr server. Changes in the location of a particular dictionary file can be made by modifying the entry in the register, avoiding the problem of specifying a URL in a data file that would then become outdated if the dictionary was moved. Dictionary applications can consult the register (according to a protocol outlined below) to locate and retrieve the dictionaries needed for validating data files. It is of course essential that the validation software knows how to locate the register. The location is at present given by the URL .

The problem of changing URLs has therefore not disappeared completely, but is at least confined to the need to maintain one single address.

Table[link] is an extract from the current register. The latest version of the register will always be available from the URL given above.

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CIF dictionary register (maintained as a STAR File)

[Scheme scheme23]

The entries for each dictionary include one with the version string set to `.', representing the current version; this is the version that should be retrieved unless a data file specifies otherwise.

Note that the register may also contain locators for local dictionaries constructed by owners of reserved prefixes (Section[link]) when the owner has requested that a dictionary of local names be made publicly available. An appropriate name for a local dictionary in the register ( _dictionary_name or _dictionary.title for DDL1 or DDL2 dictionaries, respectively) would be cif_local_myprefix.dic, where the string indicated by myprefix is one of the prefixes reserved for private use by the author of the dictionary (see Section[link]). This scheme complements the naming convention for public dictionaries.

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