International
Tables for
Crystallography
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. 23

Section 2.2.5.1. Data-name semantics

S. R. Halla* and J. D. Westbrookb

2.2.5.1. Data-name semantics

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It is a fundamental principle of the STAR File approach that a data name is simply an arbitrary string acting as an index to a required value or set of values. It is equally legitimate to store the value of a crystal cell volume either as [Scheme scheme2] or as [Scheme scheme3] provided that the users of the file have some way of discovering that the cell volume is indeed indexed by the tag _bdouiGFG78=z or _cell_volume, as appropriate.

However, it is conventional in CIF applications to define (in public dictionary files) data names that imply by their construction the meaning of the data that they index. Chapter 3.1[link] discusses the principles that are recommended for constructing data names and defining them in public dictionaries, and for utilizing private data names that will not conflict with those in the public domain.

Careful construction of data names according to the principles of Chapter 3.1[link] results in a text file that is intelligible to a scientist browsing it in a text editor without access to the associated dictionary definition files. In many ways this is useful; it allows the CIF to be viewed and understood without specialized software tools, and it safeguards some understanding of the content if the associated dictionaries cannot be found. On the other hand, there is a danger that well intentioned users may gratuitously invent data names that are similar to those in public use. It is therefore important for determining the correct semantic content of the values tagged by individual data names to make maximum possible disciplined use of the registry of public dictionaries, the registry of private data-name prefixes, and the facilities for constructing and disseminating private dictionaries discussed in Chapter 3.1[link] .








































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