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International
Tables for Crystallography Volume G Definition and exchange of crystallographic data Edited by S. R. Hall and B. McMahon © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. G. ch. 2.6, pp. 68-69
Section 2.6.6.2.1. CATEGORY
a
Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers, The State University of New Jersey, Department of Chemistry and Chemical Biology, 610 Taylor Road, Piscataway, NJ 08854-8087, USA, and bSchool of Biomedical and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia |
The category named CATEGORY contains the data items that describe the properties of collections of related data items. A DDL category is essentially a table. In this category the characteristics of the table as a whole are defined. This category includes the data items _category.id to identify a category name; _category.description to describe a category; _category.mandatory_code to indicate whether the category must appear in a data block; and _category.implicit_key, which can be used to merge like categories between data blocks. The category identifier _category.id is a component of the key in most of the DDL categories in this section. The parent definition of the category identifier and all its child relationships are defined in this category.
Because special rules exist in the STAR grammar for the specification of data items that belong to a common category, the organization of data items within categories has a significant influence on how these items may be expressed in a data file. For example, a data category may be specified only once within a STAR data block or save frame, and at any level of a STAR loop structure only data items of a common category may appear.
