Unicode Character Database

Derived Character Properties

Summary

This document describes the format and content of the main derived data files in the Unicode Character Database (UCD).

Status

The file and the files described herein are part of the Unicode Character Database and governed by the UCD Terms of Use given below.

For general information on file formats and table formats, and the implications of normative vs informative properties, see UnicodeCharacterDatabase.html.

Warning: the information in this file does not completely describe the use and interpretation of Unicode character properties and behavior. It must be used in conjunction with the data in the other files in the UCD, and relies on the notation and definitions supplied in The Unicode Standard. All chapter references are to Version 3.1.0 of the standard.

Introduction

This document describes a number of data files in the Unicode Character database. These are the Derived data files, containing information that can be completely derived from other data files, but is presented in a different format for ease of use.

The files themselves are informative, although they may contain normative properties. For more information, see UnicodeCharacterDatabase.html.

Derived Core Properties

The following are important derived properties of Unicode characters, and are contained in DerivedCoreProperties.txt.

Closure Note: XID_Start and XID_Continue are defined by adding or removing certain special characters as per UAX #15, Annex 7. They do not remove the non-NFKD nor the non_NFKC characters; if that is desired it needs to be a separate filter. They merely ensure that:

if isIdentifer(string)
then isIdentifier(NFKC(string))
and isIdentifier(NFKD(string))

Cf Note: The general category Cf characters are not included in ID_Continue nor in XID_Continue; they should continue identifiers, but be filtered out of the result.

For more information on identifiers, see Chapter 5, Implementation Guidelines, and UAX #15, Annex 7.

Derived Extracted Properties

The following files contain other properties of the UCD that are simply separated out, and listed in range format. These files are provided purely as a reformatting of existing data, with a certain exceptions listed below.

Bidi Note: The BidiMirrored property and the BidiMirroring property are different. The former is a normative property that indicates whether characters are mirrored in a right-to-left context in the Unicode Bidirectional Algorithm. The latter is an informative mapping of BidiMirrored characters, where possible, to characters that normally have the corresponding mirrored glyph.

Derived Normalization Properties

The properties in DerivedNormalizationProperties.txt are useful in dealing with normalization forms. In the following table, NF* refers to one of NFD, NFC, NFKC, or NFKD.

b = NFKC(Fold(a));
c = NFKC(Fold(b));
if (c != b) add mapping from a to c

QuickCheck Note: A previous version of this data was in NormalizationQuickCheck.txt. For more information, see UAX #15 Annex 8.)

UCD Terms of Use

Disclaimer

The Unicode Character Database is provided as is by Unicode, Inc. No claims are made as to fitness for any particular purpose. No warranties of any kind are expressed or implied. The recipient agrees to determine applicability of information provided. If this file has been purchased on magnetic or optical media from Unicode, Inc., the sole remedy for any claim will be exchange of defective media within 90 days of receipt.

This disclaimer is applicable for all other data files accompanying the Unicode Character Database, some of which have been compiled by the Unicode Consortium, and some of which have been supplied by other sources.

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Recipient is granted the right to make copies in any form for internal distribution and to freely use the information supplied in the creation of products supporting the Unicode^TM Standard. The files in the Unicode Character Database can be redistributed to third parties or other organizations (whether for profit or not) as long as this notice and the disclaimer notice are retained. Information can be extracted from these files and used in documentation or programs, as long as there is an accompanying notice indicating the source.