Lao

Lao

Root Zone Label Generation Rules, 2nd Edition

Summary

Version2 — Root Zone LGR
Date
Tag und-Laoo (Lao)
Unicode6.3.0
ScopeDNS root zone
Source filelgr-2-lao-script-26jul17-en.xml (15.9kb)
This ruleset in other editions: 6th Edition 5th Edition 4th Edition 3rd Edition 2nd Edition 1st Edition

This ruleset is integrated into the Common (integrated set) ruleset of this release.

Description

Label Generation Rules for Lao

Overview

This file contains Label Generation Rules (LGR) for the Lao script as would be appropriate for the Root zone. For more details on this LGR, see "Proposal for a Lao Script Root Zone LGR [Proposal]". The format of this file follows [RFC 7940].

Repertoire

In addition to the 51 code points according to Section 5 “Repertoire” in [Proposal], the sequence 0EB2 0EB0 has been defined to facilitate implementation of WLE rule follows-vafter-context as a context rule. The repertoire only includes code points used by languages that are actively written in the Khmer script. The repertoire is based on [MSR-2], which is a subset of Unicode 6.3 [Unicode 6.3].

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

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Variants

This LGR defines no variants.

Character Classes

Some consonants have been given the tag of Cf, which indicates final consonants. Other character classes that have been used are semi-consonant, tone-mark, vowel-above, vowel-before, vowel-below and vowel-after. See Section 5 of the [Proposal].

Whole Label Evaluation (WLE) Rules

Default Whole Label Evaluation Rules

The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-2]. 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-before.

Lao-specific Rules

Rules provided in the LGR as described in Section 7 of [Proposal] reasonably restrict labels so that they conform to Lao syllable structure. These constraints are presented exclusively as context rules.

The rules are:

  • follows-consonant — A context rule for semi-consonant. See Section 7 in [Proposal]. (WLE Rule 1)
  • precedes-consonant — A context rule for vowel-before. See Section 7 in [Proposal]. (WLE Rule 2)
  • follows-main-consonant — A context rule for vowel-below, and vowel-above. See Section 7 in [Proposal]. (WLE Rule 3)
  • follows-C-tonemark-vabove — A context rule for vowel-after. See Section 7 in [Proposal]. (WLE Rule 4)
  • follows-vbefore-consonant-cluster — A context rule for a vowel-after sequence. It incorporates consonant-cluster. See Section 7 in [Proposal]. (WLE Rule 5)
  • follows-C-vabove-vbelow — A context rule for tone mark. See Section 7 in [Proposal]. (WLE Rule 6)
  • follows-Cf — A context rule for LAO CANCELLATION MARK ໌ (U+0ECC) . See Section 7 in [Proposal]. (WLE Rule 7)
  • repetition-mark-limit.—. A rule that limits the occurrence of LAO KO LA ໆ (U+0EC6) at the label end. See Section 7 in [Proposal]. (WLE Rule 8)

No context rules apply to “consonant” code points. For discussion, see Section 5.1 “Consonants” in [Proposal].

Methodology and Contributors

For methodology and contributors, see Sections 4 and 8 of [Proposal].

References

Reference value ("ref" attribute) 0 refers to Unicode Standard versions in which corresponding code points were initially encoded. Reference values 201, 202, 203, 204, 205, 206, & 207 correspond to sources justifying the inclusion of or classification for the corresponding code points. Single code points or ranges may have multiple source reference values.

Reference values ("ref" attribute") from 201 and up refer to specific sources cited for the corresponding code points in the "[Proposal]".

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

[MSR-2]
Integration Panel, "Maximal Starting Repertoire — MSR-2 Overview and Rationale", 14 April 2015 https://www.icann.org/en/system/files/files/msr-2-overview-14apr15-en.pdf
[Proposal]
Lao Generation Panel, "Proposal for Lao Script Root Zone LGR", https://www.icann.org/en/system/files/files/proposal-lao-lgr-31jan17-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.
[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 more details for references, refer to the Table of References below. Several of these references refer to a figure in an appendix of the [Proposal] document.

Repertoire

Glyph Code point Tags and context Variants
ກ U+0E81 LAO LETTER KO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຂ U+0E82 LAO LETTER KHO SUNG 0 201 204 Lao TagconsonantTagsc:Laoo
ຄ U+0E84 LAO LETTER KHO TAM 0 201 204 Lao TagconsonantTagsc:Laoo
ງ U+0E87 LAO LETTER NGO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຈ U+0E88 LAO LETTER CO 0 201 204 Lao TagconsonantTagsc:Laoo
ຊ U+0E8A LAO LETTER SO TAM 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຍ U+0E8D LAO LETTER NYO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ດ U+0E94 LAO LETTER DO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຕ U+0E95 LAO LETTER TO 0 201 204 Lao TagconsonantTagsc:Laoo
ຖ U+0E96 LAO LETTER THO SUNG 0 201 204 Lao TagconsonantTagsc:Laoo
ທ U+0E97 LAO LETTER THO TAM 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ນ U+0E99 LAO LETTER NO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ບ U+0E9A LAO LETTER BO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ປ U+0E9B LAO LETTER PO 0 201 204 Lao TagconsonantTagsc:Laoo
ຜ U+0E9C LAO LETTER PHO SUNG 0 201 204 Lao TagconsonantTagsc:Laoo
ຝ U+0E9D LAO LETTER FO TAM 0 201 204 Lao TagconsonantTagsc:Laoo
ພ U+0E9E LAO LETTER PHO TAM 0 201 204 Lao TagconsonantTagsc:Laoo
ຟ U+0E9F LAO LETTER FO SUNG 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ມ U+0EA1 LAO LETTER MO 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຢ U+0EA2 LAO LETTER YO 0 201 204 Lao TagconsonantTagsc:Laoo
ຣ U+0EA3 LAO LETTER LO LING 0 204 Lao TagCfTagconsonantTagsc:Laoo
ລ U+0EA5 LAO LETTER LO LOOT 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ວ U+0EA7 LAO LETTER WO 0 201 204 205 Lao TagCfTagconsonantTagsc:Laoo
ສ U+0EAA LAO LETTER SO SUNG 0 201 204 Lao TagCfTagconsonantTagsc:Laoo
ຫ U+0EAB LAO LETTER HO SUNG 0 201 204 Lao TagconsonantTagsc:Laoo
ອ U+0EAD LAO LETTER O 0 201 204 205 Lao TagconsonantTagsc:Laoo
ຮ U+0EAE LAO LETTER HO TAM 0 201 204 Lao TagconsonantTagsc:Laoo
ະ U+0EB0 LAO VOWEL SIGN A 0 201 205 206 Lao Tagsc:LaooTagvowel-after Contextfollows-C-tonemark-vabove
ັ U+0EB1 LAO VOWEL SIGN MAI KAN 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
າ U+0EB2 LAO VOWEL SIGN AA 0 201 205 206 Lao Tagsc:LaooTagvowel-after Contextfollows-C-tonemark-vabove
າະ U+0EB2U+0EB0 sequence of 2 LAO VOWEL SIGN AA + LAO VOWEL SIGN A 205 Lao Contextfollows-vbefore-consonant-cluster
ິ U+0EB4 LAO VOWEL SIGN I 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
ີ U+0EB5 LAO VOWEL SIGN II 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
ຶ U+0EB6 LAO VOWEL SIGN Y 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
ື U+0EB7 LAO VOWEL SIGN YY 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
ຸ U+0EB8 LAO VOWEL SIGN U 0 201 205 206 Lao Tagsc:LaooTagvowel-below Contextfollows-main-consonant
ູ U+0EB9 LAO VOWEL SIGN UU 0 201 205 206 Lao Tagsc:LaooTagvowel-below Contextfollows-main-consonant
ົ U+0EBB LAO VOWEL SIGN MAI KON 0 205 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant
ຼ U+0EBC LAO SEMIVOWEL SIGN LO 0 201 205 206 Lao Tagsc:LaooTagsemi-consonant Contextfollows-consonant
ຽ U+0EBD LAO SEMIVOWEL SIGN NYO 0 201 205 Lao Tagsc:LaooTagvowel-after Contextfollows-C-tonemark-vabove
ເ U+0EC0 LAO VOWEL SIGN E 0 201 205 206 Lao Tagsc:LaooTagvowel-before Contextprecedes-consonant
ແ U+0EC1 LAO VOWEL SIGN EI 0 201 205 206 Lao Tagsc:LaooTagvowel-before Contextprecedes-consonant
ໂ U+0EC2 LAO VOWEL SIGN O 0 201 205 206 Lao Tagsc:LaooTagvowel-before Contextprecedes-consonant
ໃ U+0EC3 LAO VOWEL SIGN AY 0 201 205 206 Lao Tagsc:LaooTagvowel-before Contextprecedes-consonant
ໄ U+0EC4 LAO VOWEL SIGN AI 0 201 205 206 Lao Tagsc:LaooTagvowel-before Contextprecedes-consonant
ໆ U+0EC6 LAO KO LA 0 203 LAO MAY SAM Tagsc:LaooTagsign Contextrepetition-mark-limit
່ U+0EC8 LAO TONE MAI EK 0 202 Lao Tagsc:LaooTagtone-mark Contextfollows-C-vabove-vbelow
້ U+0EC9 LAO TONE MAI THO 0 202 Lao Tagsc:LaooTagtone-mark Contextfollows-C-vabove-vbelow
໊ U+0ECA LAO TONE MAI TI 0 202 LAO TONE MAI JATTAWA Tagsc:LaooTagtone-mark Contextfollows-C-vabove-vbelow
໋ U+0ECB LAO TONE MAI CATAWA 0 202 LAO MARK MAI KA LAN Tagsc:LaooTagtone-mark Contextfollows-C-vabove-vbelow
໌ U+0ECC LAO CANCELLATION MARK 0 207 LAO VOWEL SIGN OR Tagsc:LaooTagsign Contextfollows-Cf
ໍ U+0ECD LAO NIGGAHITA 0 201 205 206 Lao Tagsc:LaooTagvowel-above Contextfollows-main-consonant

Character classes

Named sets of code points that the rules below refer to.

NameDefinition
Cf {tag Cf}
consonant {tag consonant}
semi-consonant {tag semi-consonant}
tone-mark {tag tone-mark}
vowel-above {tag vowel-above}
vowel-below {tag vowel-below}

Rules

Conditions evaluated against a whole label, or against the context around a single code point. The notation borrows from regular expressions: ^ and $ anchor to the start and end of a label, . matches any code point, (?= ) and (?<= ) look ahead and behind, and * and + repeat. Two symbols are specific to rulesets: ◆ is the code point being tested, and ⟨name⟩ refers to another rule.

leading-combining-mark MSR default

Default WLE rule from MSR-2 matching labels with leading combining marks

^ ({gc:Mn} ∪ {gc:Mc})
Structure
  • ^ start
  • ({gc:Mn} ∪ {gc:Mc}) union
    • {gc:Mn} class
    • {gc:Mc} class
Referenced by 1 definition
  • action 1 (invalid)

follows-consonant

WLE Rule 1: A semi-consonant must follow a consonant

(?<= {consonant} ) ◆
Structure
  • (?<= {consonant} ) look-behind
    • {consonant} class
  • ◆ anchor
Referenced by 1 definition
  • context of U+0EBC

precedes-consonant

WLE Rule 2: A vowel-before precedes a main consonant cluster

◆ (?= {consonant} )
Structure
  • ◆ anchor
  • (?= {consonant} ) look-ahead
    • {consonant} class
Referenced by 5 definitions
  • context of U+0EC0
  • context of U+0EC1
  • context of U+0EC2
  • context of U+0EC3
  • context of U+0EC4

follows-main-consonant

WLE Rule 3: A vowel-above, and vowel-below follow a main consonant C

(?<= ( {consonant} │ {semi-consonant} ) ) ◆
Structure
  • (?<= ( {consonant} │ {semi-consonant} ) ) look-behind
    • ( {consonant} │ {semi-consonant} ) choice
      • {consonant} class
      • {semi-consonant} class
  • ◆ anchor
Referenced by 9 definitions
  • context of U+0EB1
  • context of U+0EB4
  • context of U+0EB5
  • context of U+0EB6
  • context of U+0EB7
  • context of U+0EB8
  • context of U+0EB9
  • context of U+0EBB
  • context of U+0ECD

follows-C-tonemark-vabove

WLE Rule 4: A vowel-after follows a main consonant, tone-mark or vowel-above

(?<= ( {consonant} │ {semi-consonant} │ {tone-mark} │ {vowel-above} ) ) ◆
Structure
  • (?<= ( {consonant} │ {semi-consonant} │ {tone-mark} │ {vowel-above} ) ) look-behind
    • ( {consonant} │ {semi-consonant} │ {tone-mark} │ {vowel-above} ) choice
      • {consonant} class
      • {semi-consonant} class
      • {tone-mark} class
      • {vowel-above} class
  • ◆ anchor
Referenced by 3 definitions
  • context of U+0EB0
  • context of U+0EB2
  • context of U+0EBD

consonant-cluster

Defining consonant cluster for WLE Rule 5

{consonant}{1:2} {semi-consonant}{0:1}
Referenced by 1 definition
  • rule follows-vbefore-consonant-cluster

follows-vbefore-consonant-cluster

WLE Rule 5: The sequence (0EB2 0EB0) follows a vowel before, and a consonant cluster

(?<= U+0EC0 ⟨consonant-cluster⟩ ) ◆
Structure
  • (?<= U+0EC0 ⟨consonant-cluster⟩ ) look-behind
    • U+0EC0 char
    • ⟨consonant-cluster⟩ rule
  • ◆ anchor
Referenced by 1 definition
  • context of U+0EB2 U+0EB0

follows-C-vabove-vbelow

WLE Rule 6: A tone-mark follows a main consonant, vowel-above or vowel-below

(?<= ( {consonant} │ {semi-consonant} │ {vowel-above} │ {vowel-below} ) ) ◆
Structure
  • (?<= ( {consonant} │ {semi-consonant} │ {vowel-above} │ {vowel-below} ) ) look-behind
    • ( {consonant} │ {semi-consonant} │ {vowel-above} │ {vowel-below} ) choice
      • {consonant} class
      • {semi-consonant} class
      • {vowel-above} class
      • {vowel-below} class
  • ◆ anchor
Referenced by 4 definitions
  • context of U+0EC8
  • context of U+0EC9
  • context of U+0ECA
  • context of U+0ECB

follows-Cf

WLE Rule 7: The sign 0ECC can only occur after final consonants

(?<= {Cf} ) ◆
Structure
  • (?<= {Cf} ) look-behind
    • {Cf} class
  • ◆ anchor
Referenced by 1 definition
  • context of U+0ECC

repetition-mark-limit

WLE Rule 8: The sign 0EC6 can only occur 0 to 3 times at the end of the label

◆ (?= U+0EC6{0:2} $ )
Structure
  • ◆ anchor
  • (?= U+0EC6{0:2} $ ) look-ahead
    • U+0EC6{0:2} char
    • $ end
Referenced by 1 definition
  • context of U+0EC6

Actions

Actions are evaluated in the order shown. The first action whose conditions match determines the disposition of the label.

Actions in precedence order
# Disposition Conditions
1 invalid label matches leading-combining-mark labels with leading combining marks are invalid MSR default
2 invalid any variant is out-of-repertoire-var any variant label with a code point out of repertoire is invalid MSR default
3 blocked any variant is blocked any variant label containing blocked variants is blocked MSR default
4 allocatable all variants are allocatable variant labels with all variants allocatable are allocatable MSR default
5 valid any label default catch all (default action) MSR default

References

RefSource
0 The Unicode Standard 1.1, The Unicode Consortium, Mountain View, CA. 1993
Any code point originally encoded in Unicode 1.1
201 Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 1
202 Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 2
203 Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 3
204 Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 4
205 Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 5
206 Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 6
207 Lao grammar 1935, see Appendix B, Figure 7