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Label Generation Rules for the Sinhala Script

Overview

This document specifies a set of Label Generation Rules (LGR) for the Sinhala 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-Sinh]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Sinhala Script” [Ref-LGR-und-Sinh], for details, see Change History below.

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

Repertoire

The repertoire covers the Sinhala language as written with the Sinhala script and contains 72 code points for letters. In addition, 4 sequences are used in the definition of variants. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Sinhala]. (The proposal cited has been adopted for the Sinhala 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, and the number of sequences increased to 112 by adding common sequences using ZWJ (U+200D), including some with variants, for a total of 303 repertoire elements. In addition to ZWJ, the letter U+0DA6 ඦ SINHALA LETTER SANYAKA JAYANNA is defined only in the context of an enumerated sequence.

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.

Variants

The variants defined in this LGR are limited to those required for use in zones not shared with any other script. However, because it does not share cross-script variants with other script LGRs, this LGR can be mixed easily with other LGRs in the same zone.

This LGR defines variants within Sinhala as described in Section 6, “Variants”, in “[Proposal-Sinhala]”. Additionally, some of the common conjuncts have alternates which are treated as variants.

Digit Variants: The Sinhala reference LGR does not include native digits, so there are no semantic variants defined.

The LGR defines certain allocatable fallback variants as described in Section 4.5.5 “Allocatable Fallback Variants” in [Level-2-Overview]. A fallback variant is a variant label that uses substitute code points for code points or sequences not available (or not allowed) in some contexts, that would otherwise be required for a linguistically accurate rendering of some label.

When “fallback” variants are defined, two labels may be allocated: a single label with the spelling preferred by the applicant, plus a single fallback variant for that label. The fallback exclusively uses the fallback characters for any characters for which fallbacks are defined, while the “preferred” label may use any otherwise valid mix of code points. If the fallback variant is the one applied for, no other variant label is allocatable.

For sequences including one or more U+200D ‍, the LGR also includes variant sequences without the ZWJ. Because IDNA2003 was removing ZWJ in its name processing, sequences without ZWJ are treated as an allocatable fallback representations.

In-script Variant Mapping Types

In each of the fallback variant pairs defined above, the mapping type from the first element to the second is of type “fallback”, while the variant type for the other direction is “blocked”. In addition, the first element of each pair uses the reflexive mapping “r-original”. (By convention, the prefix “r-” marks a type used in a reflexive variant mapping, that is, it represents an instance of the original code point at that location in a variant label, see Section 5.3.4 in [RFC 7940].)

Variant Disposition: Except for limited exceptions for the fallback variants defined above, variants defined here result in a variant label disposition of “blocked”.

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

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.

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” in [Proposal-Sinhala].

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” in [Proposal-Sinhala].

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” in [Proposal-Sinhala].

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” in [Proposal-Sinhala].

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” in [Proposal-Sinhala].

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

Zero Width Joiner: This character is used in the formation of certain conjuncts in Sinhala. In this LGR, ZWJ (U+200D) is not listed by itself but available as part of many defined sequences.

Whole Label Evaluation (WLE) and Context Rules

Common Rules

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].

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
• 5. H: must not follow conjunct sequence

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)” in [Proposal-Sinhala].

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].

Because this LGR defines allocatable fallback variants the following default actions are applicable.

• blocked — a variant label containing a blocked variant will receive a disposition of “blocked”.
• r-original — a label containing one or more of this reflexive variant type and no others represents an original label and receives a disposition of “valid”.
• fallback — a label containing one or more of these variant types and no others represents a label that contains only fallback variants and receives a disposition of “allocatable”.
• fallback plus other — any label remaining containing both this variant type and any others receives a disposition of “blocked”.

These actions resolve as “allocatable” any label where all variants are of type “fallback”, and as “valid” any label where all variants are of type “r-original”. Labels with a mix of variant types are resolved as “blocked”.

To account for original code points in a permuted variant, reflexive variant mappings with an “r-” prefix are used. (See [RFC 7940]). In particular, the mapping type “r-original” is given to any code point that has a fallback mapping, but that appears in its non-fallback form in the original label, and thus “maps to itself”.

Default actions that are triggered by the LGR-specific variant types described above limit the “allocatable” variant labels to those variants resulting from removal of ZWJ, while disallowing mixed use of variants with or without ZWJ, except as in the original applied-for label.

Note that the mapping types for variants are not symmetric: they depend on which code point is considered the source or the target in a given mapping. As specified in [RFC 7940], when mapping types are evaluated code points in a label that are unchanged use the type of their “reflexive” mapping. Per [RFC 7940] the actions are always applied one after the other, and the evaluation stops at the first action that assigns a disposition to a given label.

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

Changes from Version Dated 22 April 2021

Unicode Version has been updated.

Fallback variants have been added to sequences including ZWJ. These fallback variants do not contain ZWJ to provide compatibility with IDNA:2003 compliant labels.

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Sinhala Script [Ref-LGR-und-Sinh] 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-Sinhala]

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,
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-Sinh]

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

[Ref-LGR-und-Sinh]

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

For references consulted particularly in designing the repertoire for the Sinhala 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-Sinhala] 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.