Root Zone Label Generation Rules for the Sinhala Script

Overview

This file contains Label Generation Rules (LGR) for the Sinhala script for the Root zone. For more details on this LGR and its development, see "Proposal for a Sinhala Script Root Zone Label Generation Rules-Set (LGR)" [Proposal]. The format of this file follows [RFC 7940].

Repertoire

According to Section 5, "Repertoire" in [Proposal], the Sinhala LGR contains 72 unique code points. The addition of 4 sequences used in the definition of variants brings the total repertoire entries to 76. The repertoire covers the Sinhala language as written with the Sinhala script.

The repertoire is based on [MSR-4], which is a subset of [Unicode 6.3].

Each code point is tagged with the script or scripts that the code point is used with, a category value, and one or more references documenting sufficient justification for inclusion in the repertoire, see "References" below.

Variants

According to Section 6, "Variants", in [Proposal], this LGR defines variants within Sinhala which can cause confusion for even a careful observer. There are no cross-script variants, though some confusing cases are identified in [Proposal].

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.

This LGR does not define allocatable variants.

Context Rules for Variants: for some of the variants defined in this LGR the sequences or code points making up source and target are constrained by explicit context rules on the code points (or by implicit context rules defined for the adjacent code points). In such a case, any variants may require context rules that match the intersection between the effective contexts for both source and target; otherwise, a sequence might be considered valid in some variant label when it would not be valid in an equivalent context in an original label. Symmetry requires the same context rule for both forward and reverse mappings.

The specification of variants in the Root Zone LGR follows the guidelines in [RFC 8228].

Character Classes

As most Brahmi-derived scripts, Sinhala is an alphasyllabary writing system and written from left to right. All the categories of Consonants, Vowels, Matras, Halant, Anusvara, Visarga and Sannjakas are discussed below.

Consonants: There are 40 consonants in Sinhala alphabet and 38 of them are selected for inclusion. Its consonants imply inherent vowel a(අ) when they are used without dependent vowels. Absence of the inherent vowel is marked by adding hal kirima (remover of the inherent vowel) to the consonant; thus ක /ka/ but ක් /k/, and ව /va/ but ව් /v/. More details in Section 3.3.1, "The Consonants" of the [Proposal].

Vowels and Matras: There are separate symbols (dependent vowels) for all the vowels except the inherent vowel අ in Sinhala. Independent vowels are used at the beginning of a word and dependent vowels (matras) are used after consonants. More details in Section 3.3.2, "The Vowels" of the [Proposal].

Halanta: The Halanta, which is also called halkirima or hallakuna, is encoded as U+0DCA ( ් ) SINHALA SIGN AL-LAKUNA. This sign is used to remove the inherent vowel of the consonants in Sinhala, and to join consonants and form conjunct characters. More details in Section 3.3.3, "Halanta: The Inherent Vowel Remover" of the [Proposal].

Anusvara: U+0D82 ( ං ) SINHALA SIGN ANUSVARAYA, pronounced /ŋ/, represents all the nasals. It can be preceded by any sign except halanta (U+0DCA). More details in Section 3.3.4, "The Anusvara" of the [Proposal].

Visarga: U+0D83 ( ඃ ) SINHALA SIGN VISARGAYA is a rarely used sign and pronounced as /h/. It can be preceded by any sign except halanta (U+0DCA). More details in Section 3.3.5, "The Visarga" of the [Proposal].

Sannjakas: There are five separate letters for prenasalized voiced stops called sannjakas in Sinhala. From among these, ඦ is not frequently used. One specification of Sannjakas is they cannot be followed by halanta. More details in Section 3.3.6, "Sannjakas" of the [Proposal].

Whole Label Evaluation (WLE) and Context Rules

Default Whole Label Evaluation Rules and Actions

The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-4]. They are marked with ⍟. The default prohibition on leading combining marks is equivalent to ensuring that a label only starts with a consonant or vowel.

Sinhala-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 / Vowel Signs
V → Vowel
B → Anusvara (Bindu)
X → Visarga
H → Halanta / Virama
J → Sannjaka

The rules are:

• 1. H: must be preceded by C
• 2. M: must be preceded by C or J
• 3. X: must be preceded by either V, C, or M
• 4. B: must be preceded by either V, C, J or M

The following context rules apply to code points in variant sets to ensure the variant transitivity.

• 5. variants are undefined preceding a Halant or Matra
• 6. variants are undefined preceding an Anusvara, Visarga, Halant or Matra

More details in Section 7,"Whole Label Evaluation Rules (WLE)" of the [Proposal]

Methodology and Contributors

The Sinhala LGR was developed by the Sinhala Generation Panel in consultation with the Neo-Brahmi Generation Panel. For methodology and contributors, see Sections 4 and 8 of [Proposal].

References

The following general references are cited in this document:

[MSR-4]

Integration Panel, "Maximal Starting Repertoire — MSR-4 Overview and Rationale", 7 February 2019,
https://www.icann.org/en/system/files/files/msr-4-overview-25jan19-en.pdf

[Proposal]

Sinhala Generation Panel, “Proposal for a Sinhala Script Root Zone Label Generation Ruleset (LGR)”, 22 April 2019,
https://www.icann.org/en/system/files/files/proposal-sinhala-lgr-22apr19-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

[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/

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.