Unicode Character Database

Unicode Data File Format

Summary

This document describes the format and content of the UnicodeData.txt file 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 the format of the UnicodeData.txt file, which is one of the files in the Unicode Character Database. The document is divided into the following sections:

• Field Formats
  • General Category
  • Bidirectional Category
  • Character Decomposition Mapping
  • Canonical Combining Classes
  • Decompositions and Normalization
  • Case Mappings
• Property Invariants
• Modification History

Field Formats

Each line represents the data for one encoded character in the Unicode Standard. (For information on the file format, see UCD File Format in UnicodeCharacterDatabase.html).

Every encoded character has a data entry, with the exception of certain special ranges, as detailed below.

• These ranges represented only by their start and end characters, since the properties in the file are uniform, except for code values (which are all sequential and assigned).
• The names of CJK ideograph characters and the names and decompositions of Hangul syllable characters are algorithmically derivable. (See the Unicode Standard and Unicode Standard Annex #15 for more information).
• Surrogate code values and private use characters have no names.
• The supplementary Private Use characters (U+F0000 .. U+FFFFD, U+100000 .. U+10FFFD) are listed as distinct ranges. These correspond to surrogate pairs where the first surrogate is in the High Surrogate Private Use section.

The exact ranges represented by start and end characters are:

• CJK Ideographs Extension A (U+3400 .. U+4DB5)
• CJK Ideographs (U+4E00 .. U+9FA5)
• Hangul Syllables (U+AC00 .. U+D7A3)
• Non-Private Use High Surrogates (U+D800 .. U+DB7F)
• Private Use High Surrogates (U+DB80 .. U+DBFF)
• Low Surrogates (U+DC00 .. U+DFFF)
• The Private Use Area (U+E000 .. U+F8FF)
• CJK Ideographs Extension B (U+20000 .. U+2A6D6)
• Plane 15 Private Use Area (U+F0000 .. U+FFFFD)
• Plane 16 Private Use Area (U+100000 .. U+10FFFD)

The following table describes the format and meaning of each field in a data entry in the UnicodeData file.

General Category

The values in this field are abbreviations for the following values. For more information, see the Unicode Standard.

Note: the standard does not assign information to control characters (except for certain cases in the Bidirectional Algorithm). Implementations will generally also assign categories to certain control characters, notably CR and LF, according to platform conventions. See UAX #13: Unicode Newline Guidelines for more information.

Note: The term "L&" is sometimes used to stand for Uppercase, Lowercase or Titlecase letters (Lu, Ll, or Lt).

Bidirectional Category

Please refer to Chapter 3 for an explanation of the algorithm for Bidirectional Behavior and an explanation of the significance of these categories. An up-to-date version can be found on Unicode Standard Annex #9: The Bidirectional Algorithm.

Character Decomposition Mapping

The tags supplied with certain decomposition mappings generally indicate formatting information. Where no such tag is given, the mapping is designated as canonical. Conversely, the presence of a formatting tag also indicates that the mapping is a compatibility mapping and not a canonical mapping. In the absence of other formatting information in a compatibility mapping, the tag is used to distinguish it from canonical mappings.

In some instances a canonical mapping or a compatibility mapping may consist of a single character. For a canonical mapping, this indicates that the character is a canonical equivalent of another single character. For a compatibility mapping, this indicates that the character is a compatibility equivalent of another single character. The compatibility formatting tags used are:

Reminder: There is a difference between decomposition and decomposition mapping. The decomposition mappings are defined in the UnicodeData, while the decomposition (also termed "full decomposition") is defined in Chapter 3 to use those mappings recursively.

• The canonical decomposition is formed by recursively applying the canonical mappings, then applying the canonical reordering algorithm.
• The compatibility decomposition is formed by recursively applying the canonical and compatibility mappings, then applying the canonical reordering algorithm.

Canonical Combining Classes

Note: some of the combining classes in this list do not currently have members but are specified here for completeness.

Decompositions and Normalization

Decomposition is specified in Chapter 3. Unicode Standard Annex #15: Unicode Normalization Forms specifies the interaction between decomposition and normalization. That report specifies how the decompositions defined in UnicodeData.txt are used to derive normalized forms of Unicode text.

Note that as of the 2.1.9 update of the Unicode Character Database, the decompositions in the UnicodeData.txt file can be used to recursively derive the full decomposition in canonical order, without the need to separately apply canonical reordering. However, canonical reordering of combining character sequences must still be applied in decomposition when normalizing source text which contains any combining marks.

Case Mappings

There are a number of complications to case mappings that occur once the repertoire of characters is expanded beyond ASCII. For more information, see UTR #21: Case Mappings.

For compatibility with existing parsers, UnicodeData.txt only contains case mappings for characters where they are one-to-one mappings; it also omits information about context-sensitive case mappings. Information about these special cases can be found in a separate data file, SpecialCasing.txt.

Property Invariants

Values in UnicodeData.txt are subject to correction as errors are found; however, some characteristics of the categories themselves can be considered invariants. Applications may wish to take these invariants into account when choosing how to implement character properties. For more information, see Unicode Policies.

The following is a partial list of known invariants for the Unicode Character Database.

Database Fields

• The number of fields in UnicodeData.txt is fixed.
• The order of the fields is also fixed.
  • Any additional information about character properties to be added in the future will appear in separate data tables, rather than being added on to the existing table or by subdivision or reinterpretation of existing fields.

General Category

• There will never be more than 32 General Category values.
  • It is very unlikely that the Unicode Technical Committee will subdivide the General Category partition any further, since that can cause implementations to misbehave. Because the General Category is limited to 32 values, 5 bits can be used to represent the information, and a 32-bit integer can be used as a bitmask to represent arbitrary sets of categories.

Combining Classes

• Combining classes are limited to the values 0 to 255.
  • In practice, there are far fewer than 256 values used. Implementations may take advantage of this fact for compression, since only the ordering of the non-zero values matters for the Canonical Reordering Algorithm. It is possible for up to 256 values to be used in the future; however, UTC decisions in the future may restrict the number of values to 128, since this has implementation advantages. [Signed bytes can be used without widening to ints in Java, for example.]
• All characters other than those of General Category M* have the combining class 0.
  • Currently, all characters other than those of General Category Mn have the value 0. However, some characters of General Category Me or Mc may be given non-zero values in the future.
  • The precise values above the value 0 are not invariant--only the relative ordering is considered normative. For example, it is not guaranteed in future versions that the class of U+05B4 will be precisely 14.

Canonical Decomposition

• Canonical mappings are always in canonical order.
• Canonical mappings have only the first of a pair possibly further decomposing.
• Canonical decompositions are "transparent" to other character data:
  • BIDI(a) = BIDI(principal(canonicalDecomposition(a))
  • Category(a) = Category(principal(canonicalDecomposition(a))
  • CombiningClass(a) = CombiningClass(principal(canonicalDecomposition(a))
    where principal(a) is the first character not of type Mn, or the first character if all characters are of type Mn.
• However, because there are sometimes missing case pairs, and because of some legacy characters, it is only generally true that:
  • upper(canonicalDecomposition(a)) = canonicalDecomposition(upper(a))
  • lower(canonicalDecomposition(a)) = canonicalDecomposition(lower(a))
  • title(canonicalDecomposition(a)) = canonicalDecomposition(title(a))

Modification History

This section provides a summary of the changes between update versions of the Unicode Standard.

Unicode 3.1

Modifications made for Version 3.0.1 of UnicodeData.txt include:

• Addition of 2237 new entries, to cover new characters and new ranges of unified Han characters encoded in Unicode 3.1.
• Changed General Category value of 16EE..16F0 (Runic golden numbers) from No to Nl.

Unicode 3.0.1

Modifications made for Version 3.0.1 of UnicodeData.txt include:

• Added 5- and 6-digit representation of code points past U+FFFF.
• Added Private Use range definitions for Planes 15 and 16.
• Minor additions for the 10646 comment field.

Unicode 3.0.0

Modifications made for Version 3.0.0 of UnicodeData.txt include many new characters and a number of property changes. These are summarized in Appendex D of The Unicode Standard, Version 3.0.

Unicode 2.1.9

Modifications made for Version 2.1.9 of UnicodeData.txt include:

• Corrected combining class for U+05AE HEBREW ACCENT ZINOR.
• Corrected combining class for U+20E1 COMBINING LEFT RIGHT ARROW ABOVE
• Corrected combining class for U+0F35 and U+0F37 to 220.
• Corrected combining class for U+0F71 to 129.
• Added a decomposition for U+0F0C TIBETAN MARK DELIMITER TSHEG BSTAR.
• Added  decompositions for several Greek symbol letters: U+03D0..U+03D2, U+03D5, U+03D6, U+03F0..U+03F2.
• Removed  decompositions from the conjoining jamo block: U+1100..U+11F8.
• Changes to decomposition mappings for some Tibetan vowels for consistency in normalization. (U+0F71, U+0F73, U+0F77, U+0F79, U+0F81)
• Updated the decomposition mappings for several Vietnamese characters with two diacritics (U+1EAC, U+1EAD, U+1EB6, U+1EB7, U+1EC6, U+1EC7, U+1ED8, U+1ED9), so that the recursive decomposition can be generated directly in canonically reordered form (not a normative change).
• Updated the decomposition mappings for several Arabic compatibility characters involving shadda (U+FC5E..U+FC62, U+FCF2..U+FCF4), and two Latin characters (U+1E1C, U+1E1D), so that the decompositions are generated directly in canonically reordered form (not a normative change).
• Changed BIDI category for: U+00A0 NO-BREAK SPACE, U+2007 FIGURE SPACE, U+2028 LINE SEPARATOR.
• Changed BIDI category for extenders of General Category Lm: U+3005, U+3021..U+3035, U+FF9E, U+FF9F.
• Changed General Category and BIDI category for the Greek numeral signs: U+0374, U+0375.
• Corrected General Category for U+FFE8 HALFWIDTH FORMS LIGHT VERTICAL.
• Added Unicode 1.0 names for many Tibetan characters (informative).

Unicode 2.1.8

Modifications made for Version 2.1.8 of UnicodeData.txt include:

• Added combining class 240 for U+0345 COMBINING GREEK YPOGEGRAMMENI so that decompositions involving iota subscript are derivable directly in canonically reordered form; this also has a bearing on simplification of casing of polytonic Greek.
• Changes in decompositions related to Greek tonos. These result from the clarification that monotonic Greek "tonos" should be equated with U+0301 COMBINING ACUTE, rather than with U+030D COMBINING VERTICAL LINE ABOVE. (All Greek characters in the Greek block involving "tonos"; some Greek characters in the polytonic Greek in the 1FXX block.)
• Changed decompositions involving dialytika tonos. (U+0390, U+03B0)
• Changed ternary decompositions to binary. (U+0CCB, U+FB2C, U+FB2D) These changes simplify normalization.
• Removed canonical decomposition for Latin Candrabindu. (U+0310)
• Corrected error in canonical decomposition for U+1FF4.
• Added compatibility decompositions to clarify collation tables. (U+2100, U+2101, U+2105, U+2106, U+1E9A)
• A series of general category changes to assist the convergence of of Unicode definition of identifier with ISO TR 10176:
  • So > Lo: U+0950, U+0AD0, U+0F00, U+0F88..U+0F8B
  • Po > Lo: U+0E2F, U+0EAF, U+3006
  • Lm > Sk: U+309B, U+309C
  • Po > Pc: U+30FB, U+FF65
  • Ps/Pe > Mn: U+0F3E, U+0F3F
• A series of bidi property changes for consistency.
  • L > ET: U+09F2, U+09F3
  • ON > L: U+3007
  • L > ON: U+0F3A..U+0F3D, U+037E, U+0387
• Add case mapping: U+01A6 <-> U+0280
• Updated symmetric swapping value for guillemets: U+00AB, U+00BB, U+2039, U+203A.
• Changes to combining class values. Most Indic fixed position class non-spacing marks were changed to combining class 0. This fixes some inconsistencies in how canonical reordering would apply to Indic scripts, including Tibetan. Indic interacting top/bottom fixed position classes were merged into single (non-zero) classes as part of this change. Tibetan subjoined consonants are changed from combining class 6 to combining class 0. Thai pinthu (U+0E3A) moved to combining class 9. Moved two Devanagari stress marks into generic above and below combining classes (U+0951, U+0952).
• Corrected placement of semicolon near symmetric swapping field. (U+FA0E, etc., scattered positions to U+FA29)

Version 2.1.7

This version was for internal change tracking only, and never publicly released.

Version 2.1.6

This version was for internal change tracking only, and never publicly released.

Unicode 2.1.5

Modifications made for Version 2.1.5 of UnicodeData.txt include:

• Changed decomposition for U+FF9E and U+FF9F so that correct collation weighting will automatically result from the canonical equivalences.
• Removed canonical decompositions for U+04D4, U+04D5, U+04D8, U+04D9, U+04E0, U+04E1, U+04E8, U+04E9 (the implication being that no canonical equivalence is claimed between these 8 characters and similar Latin letters), and updated 4 canonical decompositions for U+04DB, U+04DC, U+04EA, U+04EB to reflect the implied difference in the base character.
• Added Pi, and Pf categories and assigned the relevant quotation marks to those categories, based on the Unicode Technical Corrigendum on Quotation Characters.
• Updating of many bidi properties, following the advice of the ad hoc committee on bidi, and to make the bidi properties of compatibility characters more consistent.
• Changed category of several Tibetan characters: U+0F3E, U+0F3F, U+0F88..U+0F8B to make them non-combining, reflecting the combined opinion of Tibetan experts.
• Added case mapping for U+03F2.
• Corrected case mapping for U+0275.
• Added titlecase mappings for U+03D0, U+03D1, U+03D5, U+03D6, U+03F0.. U+03F2.
• Corrected compatibility label for U+2121.
• Add specific entries for all the CJK compatibility ideographs, U+F900..U+FA2D, so the canonical decomposition for each (the URO character it is equivalent to) can be carried in the database.

Version 2.1.4

This version was for internal change tracking only, and never publicly released.

Version 2.1.3

This version was for internal change tracking only, and never publicly released.

Unicode 2.1.2

Modifications made in updating UnicodeData.txt to Version 2.1.2 for the Unicode Standard, Version 2.1 (from Version 2.0) include:

• Added two characters (U+20AC and U+FFFC).
• Amended bidi properties for U+0026, U+002E, U+0040, U+2007.
• Corrected case mappings for U+018E, U+019F, U+01DD, U+0258, U+0275, U+03C2, U+1E9B.
• Changed combining order class for U+0F71.
• Corrected canonical decompositions for U+0F73, U+1FBE.
• Changed decomposition for U+FB1F from compatibility to canonical.
• Added compatibility decompositions for U+FBE8, U+FBE9, U+FBF9..U+FBFB.
• Corrected compatibility decompositions for U+2469, U+246A, U+3358.

Version 2.1.1

This version was for internal change tracking only, and never publicly released.

Unicode 2.0.0

The modifications made in updating UnicodeData.txt for the Unicode Standard, Version 2.0 include:

• Fixed decompositions with TONOS to use correct NSM: 030D.
• Removed old Hangul Syllables; mapping to new characters are in a separate table.
• Marked compatibility decompositions with additional tags.
• Changed old tag names for clarity.
• Revision of decompositions to use first-level decomposition, instead of maximal decomposition.
• Correction of all known errors in decompositions from earlier versions.
• Added control code names (as old Unicode names).
• Added Hangul Jamo decompositions.
• Added Number category to match properties list in book.
• Fixed categories of Koranic Arabic marks.
• Fixed categories of precomposed characters to match decomposition where possible.
• Added Hebrew cantillation marks and the Tibetan script.
• Added place holders for ranges such as CJK Ideographic Area and the Private Use Area.
• Added categories Me, Sk, Pc, Nl, Cs, Cf, and rectified a number of mistakes in the database.

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