This document specifies a reference set of Label Generation Rules (LGR) for the Japanese language for the second level. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Jpan]. The format of this file follows [RFC 7940].
The Japanese language is written in a combination of elements from three Unicode scripts: Han (Kanji), Hiragana and Katakana. Collectively they have the script code “Jpan” for Japanese. For details and additional background on the Japanese script, see “Proposal for a Japanese Script Root Zone LGR” [Proposal-Japanese], including the appendices [Proposal-Japanese-Appendices].
Standalone LGR:This Reference LGR is designed to be used as is, or with suitable modifications in a zone that does not cater to IDNs other than those valid under this LGR. While it is anticipated that this LGR may be used in a zone that also supports LDH (ASCII) labels, this LGR lacks features that would allow its use in the context of another LGR in the same zone, and it may contain other features incompatible with such use.
This is a DRAFT document released for public comments and not final. Please see the announcement on the ICANN website for public comments on the Second Level Reference LGRs for details on how to submit comments.
The repertoire includes 6,356 Han characters, 85 Hiragana characters, 89 Katakana characters, and 2 Common (quasi-Kanji) characters for a subtotal of 6,532 repertoire elements. One of the common characters is shared between Han, Hiragana, and Katakana while the other one is shared between Hiragana and Katakana. This subset contains the code points used in writing the Japanese language using a repertoire appropriate for the Second Level. The repertoire is based on [MSR-5], which is a subset of [Unicode 11.0.0], and is defined in [RZ-LGR-Jpan]. It is also part of JIS X 0208:1997 [100]. For more details, see Section 5, “Repertoire” in [Proposal-Japanese].
For the second level, the repertoire has been augmented with the ASCII digits, U+0030 (0) to U+0039 (9); the ASCII lowercase letters, U+0061 (a) to U+007A (z); U+002D (-) HYPHEN-MINUS, U+3007 IDEOGRAPHIC NUMBER ZERO, and U+30FB KATAKANA MIDDLE DOT for a total of 6,571 repertoire elements.
Unlike many other non-Latin Second Level Reference LGRs, the Japanese language LGR includes the basic ASCII Latin set (a to z) because it is common practice in Japanese text to mix Japanese and ASCII. Therefore it does not create confusability or additional security risks in the context of a Second Level LGR for the Japanese language. It is also supported by current IDNA practice, see [700], for example.
Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used, one or more tag values denoting character category, and one or more references documenting sufficient justification for inclusion in the repertoire, see “References” below.
According to Sections 6 and 7 of [Proposal-Japanese] the LGR defines visually identical variants within the Japanese script. In addition, adding the ideographic number zero to the repertoire resulted in an additional variant association with the latin letter o.
All variants are of type “blocked”, making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated, while any other equivalent labels should be blocked (See Section 8 in [Proposal-Japanese]).
This LGR does not define allocatable variants.
The following source reference is used for variant entries in this LGR:
The following classes are defined for use in WLE and context rules:
The LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.
The LGR defines the following context rules.
The following WLE rule implements an additional restriction on HYPHEN-MINUS in a Japanese context.
This LGR includes the default actions for LGRs as well as the action needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940].
The LGR defines a Japanese-specific action invalidating any label containing an hyphen adjacent to Japanese characters.
This reference LGR for the Japanese language for the second level has been developed by Michel Suignard and Asmus Freytag, verified in expert reviews by Michael Everson, Nicholas Ostler, and Wil Tan, and based on multiple open public consultations.
References [0] and up refer to the Unicode Standard versions in which corresponding code points were initially encoded. For example, a reference value of [0] means a character was first encoded in Unicode Version 1.1. References [100] and up indicate that the code point is included in one of the following source references: JIS X 0208:1997, Survey on the user perception of the homographic character set specified by JGP. Entries in the table may have multiple source reference values.
In addition, the following general references are cited in this document:
In the listing of the repertoire by code point, references starting from [0] refer to the version of the Unicode Standard in which the corresponding code point was initially encoded. Other references (starting from [100]) document usage of code points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, reference [150] indicates the source for common rules. For more details, see the Table of References below.
Where links to certain references are not available, the data may be archived as part of [Proposal-Japanese].