Reference Label Generation Rules for the Telugu Script

Overview

This document specifies a reference set of Label Generation Rules (LGR) for the Telugu script for the second level. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-3-Telu]. For details and additional background on the script, see "Proposal for a Telugu Script Root Zone Label Generation Ruleset (LGR)" [Proposal-Telugu]. The format of this file follows [RFC 7940].

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.

Repertoire

The repertoire contains 63 code points for letters catering to the Telugu language written using the Telugu script. Several other languages with [EGIDS] levels above 4 were also considered in the analysis. The repertoire is a subset of [Unicode 6.3]. For more detail, see Section 5, "Repertoire" in [Proposal-Telugu]. (The proposal cited has been adopted for the Telugu 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), and U+002D (-) HYPHEN-MINUS for a total of 74 repertoire elements.

Code points outside the Telugu script that are listed in this file are targets for out-of-script variants and are identified by a reflexive (identity) variant of type "out-of-repertoire-var". They do not form part of the repertoire.

Each code point or range is tagged with the script or scripts that the code point is used with, 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

This reference LGR is designed for use in 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. Once a label has been delegated for one script, any variant labels from other scripts consisting 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.

The Telugu and Kannada scripts are closely related to each other and there are many code points in both scripts which can be confused with code points in the other script. This LGR defines many cross-script variants with Kannada. There are no in-script variants defined for Telugu. For details, see Section 6, "Variants" in [Proposal-Telugu].

Digit Variants: The Telugu reference LGR does not include native digits, so there are no variants defined. There are some homoglyph relations between Kannada and Telugu native digits, however, as the Telugu reference LGR does not support native digits, these do not give rise to variants. By transitivity, all ASCII digits are semantic variants of any cross-script native digits. Any Telugu label that is otherwise a cross-script variant of a Kannada label, will remain a variant if both labels add digits of the same value in the same position, irrespective of whether they are ASCII or (in the case of Kannada) native digits.

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 any other equivalent label should be blocked. There is no preference among these variants. If native digits were supported instead of common digits, they would require variants to corresponding Kannada digits.

This LGR does not define allocatable variants.

The specification of variants in this reference LGR follows the guidelines in [RFC 8228].

Character Classes

The Telugu orthography superficially resembles a series of circles and semi-circles. Most consonants carry a tick mark called ‘talakattu’. The writing system is classified as abugida type or alphasyllabary. The alphabet consists of vowels, consonants and modifiers. Each of these vowels and consonants has one or more secondary allographs.

Consonants: The Telugu consonants contain an implicit vowel /a/. More details in Section 3.5.4, "The Consonants" in [Proposal-Telugu].

Vowels and dependent vowel signs: There are fourteen vowel characters in the common inventory of which one is rarely used: U+0C0C (ఌ). It and the two obsolete vowels, U+0C60 (ౠ) and U+0C61 (ౡ), are excluded from this LGR. Each vowel, except U+0C05 (అ) has a dependent vowel sign, modifying the vowel of the consonant they follow. These signs may have different appearance depending on the size and shape of the consonant that functions as an anchor. More details in Section 3.5.1, "The vowels and vowel modifiers" in [Proposal-Telugu].

Anusvara or sunna: The Anusvara or sunna represents a homorganic nasal before the corresponding consonant and as a substitute to transcribe word final /mu/. Essentially, it substitutes a cluster of a Nasal Consonant+Halant before a consonant. More details in Section 3.5.2, "The Anusvara or sunna" in [Proposal-Telugu].

Visarga: Visarga denotes the glottal check.

Halant: A special sign is needed whenever the implicit vowel in the preceding consonant is stripped off. This symbol is known as the Halant. (Any vowel sign will also override the implicit vowel). More details in Section 3.5.1, "The vowels and vowel modifiers" in [Proposal-Telugu].

Whole Label Evaluation (WLE) and Context Rules

Common Rules

• 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].
• One non-ASCII code point — An IDN label must contain one non-ASCII code point, as described in Section 4.2.4 of RFC 5891 [150].

Default Actions

Actions include the default actions for LGRs as well as that needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940].

Telugu-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 (Dependent vowel signs)
V → Vowel
B → Anusvara (Bindu)
X → Visarga
H → Halant / Virama

The rules are:

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

More details in Section 7, "Whole Label Evaluation Rules (WLE)" in [Proposal-Telugu]. The numbering of the rules given here, follows that document.

Methodology and Contributors

This reference LGR for Telugu for the 2nd Level has been developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for Telugu and information contained or referenced therein, see [RZ-LGR-3-Telu]. Suitable extensions for the second level have been applied according to the [Guidelines]. The original proposal for a Root Zone LGR for the Telugu 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-Telugu], as well as [RZ-LGR-Overview].

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-06jan16-en.pdf

[EGIDS]

Expanded Graded Intergenerational Disruption Scale,
https://www.ethnologue.com/about/language-status
(Accessed on 13 Nov. 2017)

[Proposal-Telugu]

Neo-Brahmi Generation Panel, “Proposal for a Telugu Script Root Zone Label Generation Ruleset (LGR)”, 7 June 2019,
https://www.icann.org/en/system/files/files/proposal-telugu-lgr-07Jun19-en.pdf

[RFC 7940]

Davies, K. and A. Freytag, "Representing Label Generation Rulesets Using XML", RFC 7940, August 2016,
http://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 - LGR-3: Overview and Summary", 01 March 2020 (PDF),
https://www.icann.org/sites/default/files/lgr/lgr-3-overview-10jul19-en.pdf

[RZ-LGR-3-Telu]

ICANN, Root Zone Label Generation Rules for the Telugu Script (und-Telu) , 10 July 2019 (XML)
https://www.icann.org/sites/default/files/lgr/lgr-3-telugu-script-10jul19-en.xml

[Unicode 6.3]

The Unicode Consortium. The Unicode Standard, Version 6.3.0, (Mountain View, CA: The Unicode Consortium, 2013. ISBN 978-1-936213-08-5)
http://www.unicode.org/versions/Unicode6.3.0/

For references consulted particularly in designing the repertoire for the Telugu 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 [102] and above correspond to sources given in [Proposal-Telugu] justifying the inclusion of the corresponding code points. Entries in the table may have multiple source reference values.

4.1 Character Classes

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).

4.2 Whole label evaluation and context rules

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.

4.3 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.