Z-variant
Encyclopedia
In Unicode
, two glyph
s are said to be Z-variants (often spelled zVariants) if they share the same etymology but have slightly different appearances and different Unicode codepoints. For example, the Unicode characters U+8AAA 說 and U+8AAC 説 are Z-variants. The notion of Z-variance is only applicable to the “CJKV scripts” — Chinese, Japanese, Korean and Vietnamese — and is a subtopic of Han unification
.
.” The X-axis represents differences in semantics; for example, the Latin capital A (U+0041 A) and the Greek capital alpha (U+0391 Α) are represented by two distinct codepoints in Unicode, and might be termed “X-variants” (though this term is not common). The Y-axis represents significant differences in appearance though not in semantics; for example, the traditional Chinese character māo “cat” (U+8C93 貓) and the simplified Chinese character (U+732B 猫) are Y-variants.http://www.unicode.org/glossary/
The Z-axis represents minor typographical differences. For example, the Chinese characters (U+838A 莊) and (U+8358 荘) are Z-variants, as are (U+8AAA 說) and (U+8AAC 説). The glossary at Unicode.orghttp://www.unicode.org/glossary/ defines “Z-variant” as “Two CJK unified ideographs with identical semantics and unifiable shapes,” where “unifiable” is taken in the sense of Han unification.
Thus, were Han unification perfectly successful, Z-variants would not exist. They exist in Unicode because it was deemed useful to be able to “round-trip” documents between Unicode and other CJK encodings such as Big5
and CCCII
. For example, the character 莊 has CCCII encoding 21552D, while its Z-variant 荘 has CCCII encoding 2D552D. Therefore, these two variants were given distinct Unicode codepoints, so that converting a CCCII document to Unicode and back would be a lossless operation.
(of RFC 3743) dated 2002,http://tools.ietf.org/html/draft-jseng-idn-admin-02 one finds bù “no” (U+4E0D 不) and (U+F967 不) described as “font variants,” the term “Z-variant” being apparently reserved for interlanguage pairs such as the Chinese tù “rabbit” (U+5154 兔) and the Japanese to “rabbit” (U+514E 兎). However, the Unicode Consortium
's Unihan database http://www.unicode.org/charts/unihan.html treats both pairs as Z-variants.
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
, two glyph
Glyph
A glyph is an element of writing: an individual mark on a written medium that contributes to the meaning of what is written. A glyph is made up of one or more graphemes....
s are said to be Z-variants (often spelled zVariants) if they share the same etymology but have slightly different appearances and different Unicode codepoints. For example, the Unicode characters U+8AAA 說 and U+8AAC 説 are Z-variants. The notion of Z-variance is only applicable to the “CJKV scripts” — Chinese, Japanese, Korean and Vietnamese — and is a subtopic of Han unification
Han unification
Han unification is an effort by the authors of Unicode and the Universal Character Set to map multiple character sets of the so-called CJK languages into a single set of unified characters. Han characters are a common feature of written Chinese , Japanese , Korean , and—at least historically—other...
.
Differences on the Z-axis
The Unicode philosophy of codepoint allocation for CJK languages is organized along three “axesCartesian coordinate system
A Cartesian coordinate system specifies each point uniquely in a plane by a pair of numerical coordinates, which are the signed distances from the point to two fixed perpendicular directed lines, measured in the same unit of length...
.” The X-axis represents differences in semantics; for example, the Latin capital A (U+0041 A) and the Greek capital alpha (U+0391 Α) are represented by two distinct codepoints in Unicode, and might be termed “X-variants” (though this term is not common). The Y-axis represents significant differences in appearance though not in semantics; for example, the traditional Chinese character māo “cat” (U+8C93 貓) and the simplified Chinese character (U+732B 猫) are Y-variants.http://www.unicode.org/glossary/
The Z-axis represents minor typographical differences. For example, the Chinese characters (U+838A 莊) and (U+8358 荘) are Z-variants, as are (U+8AAA 說) and (U+8AAC 説). The glossary at Unicode.orghttp://www.unicode.org/glossary/ defines “Z-variant” as “Two CJK unified ideographs with identical semantics and unifiable shapes,” where “unifiable” is taken in the sense of Han unification.
Thus, were Han unification perfectly successful, Z-variants would not exist. They exist in Unicode because it was deemed useful to be able to “round-trip” documents between Unicode and other CJK encodings such as Big5
Big5
Big-5 or Big5 is a character encoding method used in Taiwan, Hong Kong, and Macau for Traditional Chinese characters.Mainland China, which uses Simplified Chinese Characters, uses the GB instead.- Organization :...
and CCCII
Chinese Character Code for Information Interchange
Chinese Character Code for Information Interchange or CCCII is a character set developed specifically to address the problem of interchange of Chinese information...
. For example, the character 莊 has CCCII encoding 21552D, while its Z-variant 荘 has CCCII encoding 2D552D. Therefore, these two variants were given distinct Unicode codepoints, so that converting a CCCII document to Unicode and back would be a lossless operation.
Confusion
There is some confusion over the exact definition of “Z-variant.” For example, in an Internet draftInternet Draft
Internet Drafts is a series of working documents published by the IETF. Typically, they are drafts for RFCs, but may be other works in progress not intended for publication as RFCs. It is considered inappropriate to rely on Internet Drafts for reference purposes...
(of RFC 3743) dated 2002,http://tools.ietf.org/html/draft-jseng-idn-admin-02 one finds bù “no” (U+4E0D 不) and (U+F967 不) described as “font variants,” the term “Z-variant” being apparently reserved for interlanguage pairs such as the Chinese tù “rabbit” (U+5154 兔) and the Japanese to “rabbit” (U+514E 兎). However, the Unicode Consortium
Unicode Consortium
The Unicode Consortium is a non-profit organization that coordinates the development of the Unicode standard. Its stated goal is to eventually replace existing character encoding schemes with Unicode and its standard Unicode Transformation Format schemes, claiming that many of the existing...
's Unihan database http://www.unicode.org/charts/unihan.html treats both pairs as Z-variants.