Label Generation Rules for the Korean Script

Overview

This document specifies a set of Label Generation Rules (LGR) for the Korean script for the second level domain or domains identified above. This LGR contains the full set of cross-script variants required for use with the following scripts: Chinese. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Kore]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Korean Script” [Ref-LGR-und-Kore], for details, see Change History below.

For details and additional background on the Korean script, see “Proposal for a Korean Script Root Zone LGR” [Proposal-Korean], including the appendices [Proposal-Korean-Appendices]. The term “Korean script” is usually synonymous with “Hangul”. However, in the context of the Korean LGR, “Korean script” refers to the union of Hangul Syllables and Han characters used in writing Korean (Hanja). Following existing practice, the LGR also allows letters from the Basic Latin set.

Repertoire

According to [Proposal-Korean], the repertoire contains 15,930 code points used to write the Korean language. The repertoire includes 11,172 Hangul syllables and 4,758 Hanja characters for a total of 15,930 code points (11,172 + 4,758). The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Korean]. (The proposal cited has been adopted for the Korean script portion of the Root Zone LGR.)

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; and U+002D - HYPHEN-MINUS, for a total of 15,967 repertoire elements.

Unlike many other non-Latin Second Level Reference LGRs, the Korean Script LGR includes the basic ASCII Latin letters (a to z) because it is common practice in Korean text to mix Korean 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 Korean script. It is also supported by current IDNA practice, see [700], for example.

Any code points outside the Korean Script repertoire that are targets for out-of-repertoire variants would be included here only if the variant is listed in this file. In this case they are identified as a reflexive (identity) variant of type “out-of-repertoire-var”. Whether or not they are listed, they do not form part of the repertoire.

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.

For more details, see Section 5 “Repertoire” in [Proposal-Korean].

Variants

Unlike other LGRs for this script, which only incude the variant definitions needed when used as standalone in their zone, this LGR contains the full set of variants needed for zones shared by more than one script. Where appropriate, cross-script variants have been defined to mutually exclude labels from different scripts that could otherwise be substituted by the users. To meet the requirement for variant transitivity, additional in-script variants may be defined as needed. Once a label has been delegated for one script, any of its variant labels consisting entirely of cross-script variants would be blocked. Any label containing at least one code point that is not a cross-script variant would be considered distinct. Because of that, even large numbers of defined cross-script variants generally do not lead to a high percentage of labels experiencing a collision across scripts.

The definition of variants included in this LGR contributes to the definition of variants in the Common LGR. Even though this LGR contains the full set of variants affecting this script, use of the Common LGR is required for actual mitigation of issues caused by using multiple languages or scripts in the same zone. For details, see Section 3, "Use of Multiple Reference LGRs in the Same Zone" in [Level-2-Overview].

There are no variants defined between Hangul syllables. However, the LGR defines 37 variant sets among Hanja, and 7 variant sets containing at least one Hangul syllable. All additional variants between in-repertoire Hanja required by integration with the Chinese LGR [CLGR] are also listed. These variant definitions are required when using this LGR together with the Common LGR in label processing, but they also reflect a certain consistency in the approach to variants across typographically related scripts. For more details, see Section 6 “Variants” in [Proposal-Korean].

Altogether, this LGR lists 289 variant sets, which can be classified as follows:

• 283 variant sets consist of variants between two or more Hanja characters that are part of this LGR repertoire. One of these variant sets also includes a Hangul syllable.
• 4 variant sets consist of variants between one or more in-repertoire Hanja character and a Hangul syllable. This includes one variant set already included in the previous group.
• 3 variant sets consist of variants between one out-of-repertoire Hanja character and a Hangul syllable. One variant set also includes one in-repertoire Hanja character.

Because one variant set is classified in both group 1 and 2, the total of variant sets is 283 + 4 + 3 - 1 = 289.

Additional variants

Where variants exist between the Chinese, Japanese and Korean scripts, out-of-repertoire variants may be defined with an out-of-repertoire-var mapping type. As result of integration, including the effects of cross-script transitivity, the number of cross-script variants listed for these scripts may be larger than defined in Section 6, “Variants” in [Proposal-Korean].

When integrated to be used with another script LGR in the same zone, this LGR may inherit additional blocked cross-script variants by integration; they may not be listed here unless they reflect resulting in-script variants. Always use an applicable merged, or Common LGR created by integration for determining cross-script collisions of labels. However, the list of in-repertoire variants in this LGR is exhaustive.

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].

Source References for Variants

The following source references are used for variant entries in this LGR:

• [201] - Korean-specific variants among Hanja (Table 1-1 in Appendix F)
• [202] - Korean-specific variants between Hangul and in-repertoire Hanja (Table 1-2 in Appendix F)
• [203] - Korean-specific variants between Hanja and out-of-repertoire Hanja (Table 1-3 in Appendix F)
• [204] - In-repertoire Hanja variants originating from [300] (Table 2-1 in Appendix F)
• [300] - in-repertoire variants originating from the Chinese LGR [CLGR]

Character Classes

This LGR defines the following named character classes:

• hanja — Hanja code points
• hangul — Hangul code points

Whole Label Evaluation (WLE) rules and Context Rules

Default Whole Label Evaluation Rules and Actions

By default, the LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.

• Hyphen Restrictions — restrictions on the allowable placement of hyphens (no leading/ending hyphen and no hyphen in positions 3 and 4). These restrictions are described in Section 4.2.3.1 of RFC 5891 [150]. They are implemented here as context rule on U+002D (-) HYPHEN-MINUS.
• Leading Combining Marks — restrictions on the allowable placement of combining marks (no leading combining mark). This rule is described in Section 4.2.3.2 of RFC 5891 [150].

Korean-specific Rules

This LGR does not define rules specific to the Korean script.

Actions

Default Actions

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].

Korean-specific Actions

A label may consist of Hangul syllables or Hanja characters only; no mixes are allowed. See also Section 7, “Whole Label Evaluation Rules (WLE)” in [Proposal-Korean].

• no-hangul-hanja-mixed-label — a WLE rule triggering a Korean-specific action invalidating any mixed labels

Methodology and Contributors

The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Korean Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Korean script and information contained or referenced therein; see [RZ-LGR-Kore]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. The original proposal for a Root Zone LGR for the Korean script, that this LGR is based on, was developed by the Korean Generation Panel. For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Korean], as well as [RZ-LGR-Overview].

Changes from Version Dated 25 October 2024

This version modifies the Second Level Reference LGR for the Korean Script [Ref-LGR-und-Kore] 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

References [0] to [3] refer to the Unicode Standard versions in which corresponding code points were initially encoded. For example, a reference value of [3] means a character was first encoded in Unicode Version 3.0.

References [101] and up indicate that the code point is included in one of the following source references: [101] ‘kIRG_KSource’ values starting by K0 in the Unihan database and [102] ‘kIICore’ values including the letter ‘K’(indicating source) in the Unihan database.

Entries in the table may have multiple source reference values.

In addition, the following general references are cited in this document:

[CLGR]

Root Zone Label Generation Rules for Chinese, 26 May 2020,
https://www.icann.org/en/system/files/files/proposal-chinese-lgr-26may20-en.xml

[Guidelines]

ICANN, “Guidelines for Developing Reference LGRs for the Second Level”, (Los Angeles, California: ICANN, 27 May 2020),
https://www.icann.org/en/system/files/files/lgr-guidelines-second-level-27may20-en.pdf

[Level-2-Overview]

Internet Corporation for Assigned Names and Numbers, (ICANN),“Reference Label Generation Rules (LGR) for the Second Level: Overview and Summary” (PDF), (Los Angeles, California: ICANN, 25 October 2024),
https://www.icann.org/en/system/files/files/level2-lgr-overview-summary-25oct24-en.pdf

[MSR-5]

Integration Panel, “Maximal Starting Repertoire — MSR-5 Overview and Rationale”, 24 June 2021,
https://www.icann.org/en/system/files/files/msr-5-overview-24jun21-en.pdf

[Proposal-Korean]

Korean Script Generation Panel (KGP), “Proposal for a Korean Script Root Zone LGR”, 1 May 2021 (PDF),
https://www.icann.org/en/system/files/files/proposal-korean-lgr-01may21-en.pdf

[Proposal-Korean-Appendices]

Appendices to “Proposal for a Korean Script Root Zone LGR”, 1 May 2021 (ZIP),
https://www.icann.org/en/system/files/files/proposal-korean-lgr-appendices-01may21-en.zip

[Ref-LGR-und-Kore]

ICANN, Second Level Reference Label Generation Rules for the Korean Script (und-Kore), 25 October 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-korean-full-variant-script-25oct24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-korean-full-variant-script-25oct24-en.html

[Ref-LGR-Chinese-Full-Variant-Script]

ICANN, Second Level Reference Label Generation Rules for the Chinese Script (und-Hani), 25 October 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-chinese-full-variant-script-25oct24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-chinese-full-variant-script-25oct24-en.html

[RFC 7940]

Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
https://www.rfc-editor.org/info/rfc7940

[RFC 8228]

A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
https://www.rfc-editor.org/info/rfc8228

[RZ-LGR-Kore]

ICANN, Root Zone Label Generation Rules for the Korean Script (und-Kore), 26 May 2022 (XML)
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-korean-script-26may22-en.xml

[RZ-LGR-Overview]

Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022 (PDF),
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-overview-26may22-en.pdf

[RZ-LGR-5]

Integration Panel, “Root Zone Label Generation Rules (RZ-LGR-5)”, 26 May 2022 (XML),
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-common-26may22-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-common-26may22-en.html

[Unicode 11.0.0]

The Unicode Consortium. The Unicode Standard, Version 11.0.0, (Mountain View, CA: The Unicode Consortium, 2018. ISBN 978-1-936213-19-1)
https://www.unicode.org/versions/Unicode11.0.0/

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 [101]) document usage of code points. 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-Korean].