《晶体 CIF 文件 语法中英对照》.docVIP

Syntax Version 1.1 Working specification Introduction Definition of terms File syntax General features Character set White space End-of-line conventions Case sensitivity Implementation restrictions Maximum line length and character set Maximum data name, block code and frame code lengths Single-level loop constructions Non-expansion of save frame references Exclusion of global_ blocks Version identification Appendix A: A formal grammar for CIF Summary Explanation of the formal syntax Lexical tokens CIF grammar References Introduction 1. This document describes the full syntax of the Crystallographic Information File (CIF). Definition of terms 2. The following terms are used in the CIF specification documents with the specific meanings indicated here. 2.1. A CIF is a file conforming to the specification herein stated, containing either information on a crystallographic experiment or its results (or similar scientific content); or descriptions of the data identifiers in such a file. 2.2. A data file is understood to convey information relating to a crystallographic experiment. 2.3. A dictionary file is understood to contain information about the data items in one or more data files as identified by their data names. 2.4. A data name is a case-insensitive identifier (a string of characters beginning with an underscore character) of the content of an associated data value. 2.5. A data value is a string of characters representing a particular item of information. It may represent a single numerical value; a letter, word or phrase; extended discursive text; or in principle any coherent unit of data such as an image, audio clip or virtual-reality object. 2.6. A data item is a specific piece of information defined by a data name and an associated data value. 2.7. A tag is understood in this document to be a synonym for data name. 2.8. A data block is the highest-level component of a CIF, containing data items or save frames. A data block is identified by a data blo