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ISO/IEC 14651:2011

Information technology -- International string ordering and comparison -- Method for comparing character strings and description of the common template tailorable ordering

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ISO/IEC 14651:2011 defines the following.

  • A reference comparison method. This method is applicable to two character strings to determine their collating order in a sorted list. The method can be applied to strings containing characters from the full repertoire of ISO/IEC 10646. This method is also applicable to subsets of that repertoire, such as those of the different ISO/IEC 8-bit standard character sets, or any other character set, standardized or not, to produce ordering results valid (after tailoring) for a given set of languages for each script. This method uses collation tables derived either from the Common Template Table defined in ISO/IEC 14651:2011 or from one of its tailorings. This method provides a reference format. The format is described using the Backus-Naur Form (BNF). This format is used to describe the Common Template Table. The format is used normatively within ISO/IEC 14651:2011.
  • A Common Template Table. A given tailoring of the Common Template Table is used by the reference comparison method. The Common Template Table describes an order for all characters encoded in ISO/IEC 10646:2011. It allows for a specification of a fully deterministic ordering. This table enables the specification of a string ordering adapted to local ordering rules, without requiring an implementer to have knowledge of all the different scripts already encoded in the UCS.
  • A reference name. The reference name refers to this particular version of the Common Template Table, for use as a reference when tailoring. In particular, this name implies that the table is linked to a particular stage of development of the ISO/IEC 10646 Universal multiple-octet coded character set.
  • Requirements for a declaration of the differences (delta) between the collation table and the Common Template Table.

ISO/IEC 14651:2011 does not mandate the following.

  • A specific comparison method; any equivalent method giving the same results is acceptable.
  • A specific format for describing or tailoring tables in a given implementation.
  • Specific symbols to be used by implementations, except for the name of the Common Template Table.
  • Any specific user interface for choosing options.
  • Any specific internal format for intermediate keys used when comparing, nor for the table used. The use of numeric keys is not mandated either.
  • A context-dependent ordering.
  • Any particular preparation of character strings prior to comparison.


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