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Label Generation Rules for the Kannada Script

Overview

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

For details and additional background on the Kannada script, see “Proposal for a Kannada Script Root Zone Label Generation Ruleset (LGR)" [Proposal-Kannada].

Repertoire

The repertoire contains 62 code points for letters covering Kannada, Tulu, Beary, Konkani, Havyaka, Kodava, among other languages written using the Kannada script. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Kannada]. (The proposal cited has been adopted for the Kannada script portion of the Root Zone LGR.)

For the second level, the repertoire has been augmented with the HYPHEN-MINUS, and two sets of decimal digits:

• European (common) digits
• Kannada digits

for a total of 83 repertoire elements.

Any code points outside the Kannada 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, one or more tag values denoting character category, and one or more references documenting sufficient justification for inclusion in the repertoire, see “References” below. Comments provide alternate names for some code points.

Variants

The variants defined in this LGR are limited to those required for use in zones not shared with any other script. As such, this LGR does not define cross-script variants. However, using this LGR concurrently with any LGR for Telugu in the same zone will create potential cross-script issues. For details, see Section 6, “Variants” in [Proposal-Kannada]. Mitigation of these cross-script variants can be addressed by using the Common LGR. For details, see Section 3, “Use of Multiple Reference LGRs in the Same Zone” in [Level-2-Overview]. In addition to variants defined by this LGR, the full variant information related to this script and required for concurrent use with the Telugu LGR(s) can be found in the following LGR: [Ref-LGR-Telugu-Full-Variant-Script]

There are no in-script variants defined for Kannada.

Digit Variants: All Kannada digits are treated as semantic variants of the corresponding common (ASCII) digits. By transitivity, they are also semantic variants of any native digits in scripts that also include the common digits. Such variant relations are deemed to exist implicitly by transitivity but are not listed explicitly in each reference LGR. Instead, if needed, they are applied by using the Common LGR in label processing.

There is a homoglyph relation between most Telugu and Kannada digits, but as the Telugu LGR does not support native digits, this does not give rise to variants.

In particular, Kannada digit ZERO is a cross-script homoglyph or near homoglyph of digit ZERO in many other scripts; these are already implicit semantic variants by transitivity and therefore not listed here.

To keep digit variant sets manageable in zones where multiple scripts are present, no attempt has been made at identifying cross-script variants among digits of different numeric value or between a digit in one script and a letter in another, such as between digit zero and Latin letter ‘o’. Other mechanisms may be required to prevent homograph labels.

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].

Character Classes

The structure of the Kannada script is similar to that of other Indian scripts; it is particularly closely related to Telugu. The heart of the writing system is the akshar. The basic characters are classified into three main categories: swara (vowels), vyanjana (consonants) and yogavahas (semiconsonants).

Swaras (vowels): There are thirteen vowels. When a vowel follows a consonant, it is written with a diacritic rather than as a separate letter. Sometimes these are referred to as vowel signs or matras. More details in Section 3.4.1, “Swaras (vowels)” in [Proposal-Kannada].

Yogavahas (semiconsonants): The Yogavaha (part-vowel, part consonant) include two letters:

1. The anusvara: ಅಂ /aṁ/.
2. The visarga: ಅಃ /aḥ/.

See Section 3.4.2, “Yogavahas” in [Proposal-Kannada].

Vyanjanas (consonants): Two categories of consonant characters are defined in Kannada: the structured consonants (vargeeya vyanjana) and the unstructured consonants (avargeeya vyanjana). For the purpose of this LGR, all consonants are treated the same. More details in Section 3.4.3, “Vyanjanas (consonants)” of the [Proposal-Kannada].

Halant / Virama: All consonant code points in Kannada contain an implicit vowel ಅ /a/. The Unicode character U+0CCD  ್ , which is the Kannada equivalent of the Devanagari Halant (or Virama), U+094D  ् , is applied to consonants to remove the implicit vowel. More details in Section 3.4.4, “Implicit vowel ಅ (a) in consonants” in [Proposal-Kannada].

Kannada Digits: U+0CE6 ೦ to U+0CEF ೯ are a set of Kannada-specific digits. They are used in alternation with the European (common) digits.

Common Digits: U+0030 0 to U+0039 9 are the set of digits from the ASCII range.

Whole Label Evaluation (WLE) and Context Rules

Common Rules

The LGR includes the rules and actions to implement the following restrictions, some of which are mandated by the IDNA protocol. They are marked with ⍟ and included here by default.

• 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].
• Digit-mixing — no mixing between different digit sets (European and Kannada digits) is allowed; implemented here as a WLE rule with associated action.

Default Actions

This LGR includes the complete set 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] and [150]. An additional action is triggered by mixed digit labels.

Kannada-specific Rules

These rules have been formulated so that they can be adopted for LGR specification.

The following symbols are used in the WLE rules:
C → Consonant
M → Matra
V → Vowel
B → Anusvara
X → Visarga
H → Halant / Virama

The rules are:

• 1. H: must be preceded by C
• 2. M: must be preceded by C
• 3. B: must be preceded by C, V or M
• 4. X: must be preceded by C, V or M
• 5. V: cannot be preceded by H

More details in Section 7, “Whole Label Evaluation Rules (WLE)” of [Proposal-Kannada].

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 Kannada Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Kannada script and information contained or referenced therein; see [RZ-LGR-Knda]. 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 Kannada script, that this reference LGR is based on, was developed by the Neo-Brahmi Generation Panel (NBGP). For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Kannada], as well as [RZ-LGR-Overview].

Changes from Version Dated 15 December 2020

Unicode Version has been updated.

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Kannada Script [Ref-LGR-und-Knda] without normative changes.

References

The following general references are cited in this document:

[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, 24 January 2024),
https://www.icann.org/en/system/files/files/level2-lgr-overview-summary-24jan24-en.pdf

[Proposal-Kannada]

Neo-Brahmi Generation Panel, “Proposal for a Kannada Script Root Zone Label Generation Ruleset (LGR)”, 6 March 2019,
https://www.icann.org/en/system/files/files/proposal-kannada-lgr-06mar19-en.pdf

[Ref-LGR-und-Knda]

ICANN, Second Level Reference Label Generation Rules for the Kannada Script (und-Knda), 24 January 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-kannada-script-24jan24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-kannada-script-24jan24-en.html

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

ICANN, Second Level Reference Label Generation Rules for the Telugu Script (und-Telu), 24 January 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-telugu-full-variant-script-24jan24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-telugu-full-variant-script-24jan24-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-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-Knda]

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

[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/

For references consulted particularly in designing the repertoire for the Kannada Script for the second level please see details in the Table of References below.

Reference [0] refers to the Unicode Standard version in which the corresponding code points were initially encoded. References [110] and above correspond to sources given in [Proposal-Kannada] justifying the inclusion of the corresponding 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.

Character Classes

Number of named classes	6
Implicit (except script)	2
Implict defined by script tag	2

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name	Definition	Count	Members or Ranges	Ref	Comment
C	Tag=Consonant	34	{0C95-0CA8 0CAA-0CB0 0CB2-0CB3 0CB5-0CB9}	[110], [111]	Any Kannada consonant
V	Tag=Vowel	13	{0C85-0C8B 0C8E-0C90 0C92-0C94}	[110], [111]	Any Kannada independent vowel
M	Tag=Matra	12	{0CBE-0CC3 0CC6-0CC8 0CCA-0CCC}	[110], [111]	Any Kannada vowel sign (matra)
H	Tag=Halant	1	{0CCD}	[110], [111]	The Kannada Halant / Virama
common-digits	Tag=Common-digit	10	{0030-0039}		Digits from the ASCII range; ⍟
kannada-digits	Tag=Kannada-digit	10	{0CE6-0CEF}		Kannada digits
implicit	Tag=Anusvara	1	{0C82}		The character tagged as Anusvara
implicit	Tag=Visarga	1	{0C83}		The character tagged as Visarga
implicit	Tag=sc:Knda	72	{0C82-0C83 0C85-0C8B 0C8E-0C90 0C92-0CA8 0CAA-0CB0 0CB2-0CB3 0CB5-0CB9 0CBE-0CC3 0CC6-0CC8 0CCA-0CCD 0CE6-0CEF}		Any character tagged as Kannada
implicit	Tag=sc:Zyyy	11	{002D 0030-0039}		Any character tagged as Common

Legend

Members or Ranges

Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".

Tag=ttt

A named or implicit class defined by all code points that share the given tag value (ttt).

Implicit

An anonymous class implicitly defined based on tag value and for which there is no named equivalent.

Whole label evaluation and context rules

Number of rules	6
Used to trigger actions	2
Used as context rule (C)	4
Anchored context rules	4

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name	Regular Expression	Used as Trigger	Anchor	Used as Context	Ref	Comment
leading-combining-mark	(start)[[\p{gc=Mn}] ∪ [\p{gc=Mc}]]	✔			[150]	RFC 5891 restrictions on placement of combining marks ⍟
hyphen-minus-disallowed	(((start))← ⚓︎)|(⚓︎ →((end)))|(((start)..\u002D)← ⚓︎)		✔	C	[150]	RFC 5891 restrictions on placement of U+002D - ⍟
follows-C	([:C:])← ⚓︎		✔	C		Section 7, WLE 1: H must be preceded by C; WLE 2: M must be preceded by C
follows-C-V-or-M	([:C:]|[:V:]|[:M:])← ⚓︎		✔	C		Section 7, WLE 3: Anusvara must be preceded by C, V or M; WLE 4: Visarga must be preceded by C, V or M
follows-H	([:H:])← ⚓︎		✔	C		Section 7, WLE 5: V cannot be preceded by H
digit-mixing	([:common-digits:].*[:kannada-digits:])|([:kannada-digits:].*[:common-digits:])	✔				restrictions on mixing digits

Legend

Used as Trigger

This rule triggers one of the actions listed below.

Used as Context

This rule defines a required or prohibited context for a code point C or variant V.

Anchor

This rule has a placeholder for the code point for which it is evaluated.

Regular Expression

A regular expression equivalent to the rule, shown in a modified notation as noted:

⚓︎ - context anchor

Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.

(...)← - look-behind

If present encloses required context preceding the anchor.

→(..) - look-ahead

If present encloses required context following the anchor.

( ) - group

An anonymous nested rule is used to group match operators.

(... | ...) - choice

When there is more than one alternative in a rule, the choices are separated by the alternation operator (...|...).

start or end

(start) matches the start of the label; (end) matches the end of the label.

. - any code point

. matches any code point.

*, +, ?, {n,m} - count operators

* indicates 0 or more, + indicates one or more, and ? indicates up to one instance. {n,m} indicates at least n and at most m instances.

[: :] - named or implicit character set

Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.

[\p{ }] - property

Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.

∪, ∩, ∖, ∆ - set operators

Sets may be combined by set operators (∪ = union, ∩ = intersection, ∖ = difference, ∆ = symmetric difference).

⍟ - default rule

Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Actions

The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

#	Condition	Rule / Variant Set		Disposition	Ref	Comment
1	if label matches	leading-combining-mark	→	invalid	[150]	labels with leading combining marks are invalid ⍟
2	if label matches	digit-mixing	→	invalid		a label violating the restriction on digit mixing is invalid
3	if at least one variant is in	{out-of-repertoire-var}	→	invalid		any variant label with a code point out of repertoire is invalid ⍟
4	if at least one variant is in	{blocked}	→	blocked		any variant label containing blocked variants is blocked ⍟
5	if each variant is in	{allocatable}	→	allocatable		variant labels with all variants allocatable are allocatable ⍟
6	if any label (catch-all)		→	valid		catch all (default action) ⍟

Legend

{...} - variant type set

In the “Rule/Variant Set” column, the notation {...} means a set of variant types.

⍟ - default action

Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.