This document specifies a set of Label Generation Rules (LGR) for the Japanese language for the second level domain or domains identified above. The ultimate starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Jpan]. Note that while it is the Japanese Script Root Zone LGR that forms the starting point, the LGR defined here covers the Japanese Language. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Japanese Language” [Ref-LGR-ja-Jpan], for details, see Change History below.
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 LGR is designed to be used in a zone that does not cater to IDNs other than those valid under this LGR. Following existing practice, this LGR also supports ASCII letters and where applicable accounts for any interaction with the remainder of the repertoire.
The repertoire contains the code points used in writing the Japanese language using a repertoire appropriate for the Second Level. It is part of JIS X 0208:1997 [100] and it 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.
The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Japanese]. (The proposal cited has been adopted for the Japanese script portion of the Root Zone LGR.)
For the second level, the repertoire has been augmented with the ASCII digits, U+0030 to U+0039; the ASCII lowercase letters, U+0061 to U+007A; 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 letters (a to z) because it is common practice in Japanese text to mix Japanese and ASCII. Therefore including these letters is not seen as creating added confusability or 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 and one or more other character categories. For each repertoire element, one or more references document sufficient justification for inclusion in the repertoire; see the “References” below.
This LGR defines visually identical variants within the Japanese script. For Details, see Sections 6, 7, and 8 of [Proposal-Japanese]. In addition, adding the ideographic number zero to the repertoire resulted in an additional variant association with the Latin letter “o”.
Variant Disposition: 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. There is no preference among these labels.
This LGR does not define allocatable variants.
The specification of variants in this LGR follows the guidelines in [RFC 8228].
The following source reference is used for variant entries in this LGR:
The following classes are defined for use in WLE and context rules:
By default, 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.
Note that U+30FB KATAKANA MIDDLE DOT is used to separate words. Therefore, the letters following a KATAKANA MIDDLE DOT must be restricted to the same set as for the start of label. For the second level, the context rule “at-start-of-word” has been defined which covers the start of a label as well as the context following a KATAKANA MIDDLE DOT.
Iteration marks: The iteration marks, U+3005, U+309D, U+309E, U+30FD, and U+30FE, are used to reiterate the pronunciation or meaning of the preceding character. As such, these characters have neither particular pronunciation nor meanings by themselves. Similar considerations apply to the prolonged sound mark (U+30FC). Accordingly, any sequence of two or more iteration marks and/or the prolonged sound mark has no meaning and is disallowed by the following WLE rule:
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 a hyphen adjacent to Japanese characters.
The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Japanese Language was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Japanese script and information contained or referenced therein; see [RZ-LGR-Jpan]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. As part of that process, features have been removed or modified as appropriate for the target language. The original proposal for a Root Zone LGR for the Japanese script, that this LGR is based on, was developed by the Japanese Generation Panel. For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Japanese], as well as [RZ-LGR-Overview].
This version modifies the Second Level Reference LGR for the Japanese Language [Ref-LGR-ja-Jpan] by injecting the complete (maximal) set of cross-repertoire variants, including any imposed by transitivity. Injected variants are marked by special comments. Any character classes, context and WLE rules required for testing are also imported. In all other respects, description or annotations have not been updated to reflect the injected variants. Any LGR elements that might pose a possible conflict when the LGR is used with the Common LGR for cross-repertoire variant resolution are clearly marked. All modifications are carried out mechanically; there may be an occasional context rule or similar that is injected because its definition relates to some repertoire element even though it can never be triggered by any label valid under the modified LGR.
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].
]]>