Root Zone LGR for script: Lao (Laoo) | lgr-4-lao-script-05nov20-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date | 2020-11-05
LGR Version | 4
Language | und-Laoo
Scope | domain: "." (Root)
Unicode Version | 6.3.0

## Table of Contents

# 1 Description

# Root Zone Label Generation Rules for the Lao Script

## Overview

This file contains Label Generation Rules (LGR) for the Lao script for the Root zone. For more details on this LGR and its development, as well as background on the script, see "Proposal for a Lao Script Root Zone LGR [Proposal-Lao]". This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-4]. The format of this file follows [RFC 7940].

## Repertoire

In addition to the 51 code points according to Section 5 “Repertoire” in [Proposal-Lao], 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-4], which is a subset of [Unicode 6.3].

As part of the Root Zone, this LGR includes neither digits nor the HYPHEN-MINUS.

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

## Variants

According to Section 6, "Variants" in [Proposal-Lao], this LGR defines no variants.

## Character Classes

Consonants: In regular syllables, consonants occur in limited combinations. However, arbitrary combinations are used for acronyms. The LGR therefore considers the restriction on syllabic combinations a matter of spelling and does not enforce them. Consonants may be followed by a semi-consonant mark. Some consonants have been given the tag "Cf", which indicates final consonants. See Section 5, "Consonants" in [Proposal-Lao].

Vowels: Vowels are divided into vowel-above, vowel-before, vowel-below and vowel-after so as to enforce some of the syllable structure using context rules. However, many details have been considered spelling issues and, for simplification, are not modeled in this LGR. See Section 5 in [Proposal-Lao].

Semi-consonant: The character U+0EBC (ຼ) LAO SEMIVOWEL SIGN LO follows consonants (see Section 5 in [Proposal-Lao]).

Tone-mark: Any of four tone marks can follow a consonant or vowel-above or vowel-below (see Section 5 in [Proposal-Lao]).

Signs: The character U+0ECC (໌) LAO CANCELLATION MARK follows a final consonant (Cf). The character U+0EC6 (ໆ) LAO KO LA is a repetition mark that can only occur up to 3 times at the end of the label (See Section 5 in [Proposal-Lao]).

## 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-before.

### Lao-specific Rules

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

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

## Methodology and Contributors

The Root Zone LGR for the Lao script was developed by the Lao Generation Panel. For methodology and contributors, see Sections 4 and 8 in [Proposal-Lao], as well as [RZ-LGR-4-Overview].

## 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-Lao]
  Lao Generation Panel, "Proposal for Lao Script Root Zone LGR",
  https://www.icann.org/en/system/files/files/proposal-lao-lgr-41jan17-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
[RZ-LGR-4-Overview]
  Integration Panel, "Root Zone Label Generation Rules - LGR-4: Overview and Summary", 05 November 2020 (PDF),
  https://www.icann.org/sites/default/files/lgr/lgr-4-overview-05nov20-en.pdf
[RZ-LGR-4]
  Integration Panel, "Label Generation Rules for the Root Zone — LGR-4", 05 November 2020 (XML),
  https://www.icann.org/sites/default/files/lgr/lgr-4-common-05nov20-en.xml
  non-normative HTML presentation:
  https://www.icann.org/sites/default/files/lgr/lgr-4-common-05nov20-en.html
[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 Lao script for the Root Zone please see details in the Table of References below. Reference [0] refers to the Unicode Standard version in which corresponding code points were initially encoded. References [201], [202], [203], [204], 205], [206], & [207] correspond to sources given in [Proposal-Lao] justifying the inclusion of or classification for the corresponding code points. Entries in the table may have multiple source reference values.

# 2 Repertoire

## Repertoire Summary

Number of elements in repertoire | 52
Number of code points | 51
Number of sequences | 1
Longest code point sequence | 2

## Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

See also the legend provided below the table.

Code Point | Glyph | Script | Name | Ref | Tags | Required Context | Comment
--- | --- | --- | --- | --- | --- | --- | ---
U+0E81 | ກ | Lao | LAO LETTER KO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E82 | ຂ | Lao | LAO LETTER KHO SUNG | [0], [201], [204] | consonant |  | Lao
U+0E84 | ຄ | Lao | LAO LETTER KHO TAM | [0], [201], [204] | consonant |  | Lao
U+0E87 | ງ | Lao | LAO LETTER NGO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E88 | ຈ | Lao | LAO LETTER CO | [0], [201], [204] | consonant |  | Lao
U+0E8A | ຊ | Lao | LAO LETTER SO TAM | [0], [201], [204] | Cf, consonant |  | Lao
U+0E8D | ຍ | Lao | LAO LETTER NYO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E94 | ດ | Lao | LAO LETTER DO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E95 | ຕ | Lao | LAO LETTER TO | [0], [201], [204] | consonant |  | Lao
U+0E96 | ຖ | Lao | LAO LETTER THO SUNG | [0], [201], [204] | consonant |  | Lao
U+0E97 | ທ | Lao | LAO LETTER THO TAM | [0], [201], [204] | Cf, consonant |  | Lao
U+0E99 | ນ | Lao | LAO LETTER NO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E9A | ບ | Lao | LAO LETTER BO | [0], [201], [204] | Cf, consonant |  | Lao
U+0E9B | ປ | Lao | LAO LETTER PO | [0], [201], [204] | consonant |  | Lao
U+0E9C | ຜ | Lao | LAO LETTER PHO SUNG | [0], [201], [204] | consonant |  | Lao
U+0E9D | ຝ | Lao | LAO LETTER FO FON | [0], [201], [204] | consonant |  | = lao letter fo sung; Lao
U+0E9E | ພ | Lao | LAO LETTER PHO TAM | [0], [201], [204] | consonant |  | Lao
U+0E9F | ຟ | Lao | LAO LETTER FO FAY | [0], [201], [204] | Cf, consonant |  | = lao letter fo tam; Lao
U+0EA1 | ມ | Lao | LAO LETTER MO | [0], [201], [204] | Cf, consonant |  | Lao
U+0EA2 | ຢ | Lao | LAO LETTER YO | [0], [201], [204] | consonant |  | Lao
U+0EA3 | ຣ | Lao | LAO LETTER RO | [0], [204] | Cf, consonant |  | = lao letter lo rada; Lao
U+0EA5 | ລ | Lao | LAO LETTER LO | [0], [201], [204] | Cf, consonant |  | = lao letter lo ling; Lao
U+0EA7 | ວ | Lao | LAO LETTER WO | [0], [201], [204], [205] | Cf, consonant |  | Lao
U+0EAA | ສ | Lao | LAO LETTER SO SUNG | [0], [201], [204] | Cf, consonant |  | Lao
U+0EAB | ຫ | Lao | LAO LETTER HO SUNG | [0], [201], [204] | consonant |  | Lao
U+0EAD | ອ | Lao | LAO LETTER O | [0], [201], [204], [205] | consonant |  | Lao
U+0EAE | ຮ | Lao | LAO LETTER HO TAM | [0], [201], [204] | consonant |  | Lao
U+0EB0 | ະ | Lao | LAO VOWEL SIGN A | [0], [201], [205], [206] | vowel-after | follows-C-tonemark-vabove | Lao
U+0EB1 | ັ | Lao | LAO VOWEL SIGN MAI KAN | [0], [201], [205], [206] | vowel-above | follows-main-consonant | Lao
U+0EB2 | າ | Lao | LAO VOWEL SIGN AA | [0], [201], [205], [206] | vowel-after | follows-C-tonemark-vabove | Lao
U+0EB2 U+0EB0 | າະ | {Lao} | LAO VOWEL SIGN AA + LAO VOWEL SIGN A | [205] | [vowel-after] + [vowel-after] | follows-vbefore-consonant-cluster | Lao
U+0EB4 | ິ | Lao | LAO VOWEL SIGN I | [0], [201], [205], [206] | vowel-above | follows-main-consonant | Lao
U+0EB5 | ີ | Lao | LAO VOWEL SIGN II | [0], [201], [205], [206] | vowel-above | follows-main-consonant | Lao
U+0EB6 | ຶ | Lao | LAO VOWEL SIGN Y | [0], [201], [205], [206] | vowel-above | follows-main-consonant | Lao
U+0EB7 | ື | Lao | LAO VOWEL SIGN YY | [0], [201], [205], [206] | vowel-above | follows-main-consonant | Lao
U+0EB8 | ຸ | Lao | LAO VOWEL SIGN U | [0], [201], [205], [206] | vowel-below | follows-main-consonant | Lao
U+0EB9 | ູ | Lao | LAO VOWEL SIGN UU | [0], [201], [205], [206] | vowel-below | follows-main-consonant | Lao
U+0EBB | ົ | Lao | LAO VOWEL SIGN MAI KON | [0], [205] | vowel-above | follows-main-consonant | Lao
U+0EBC | ຼ | Lao | LAO SEMIVOWEL SIGN LO | [0], [201], [205], [206] | semi-consonant | follows-consonant | = lao semiconsonant lo; Lao
U+0EBD | ຽ | Lao | LAO SEMIVOWEL SIGN NYO | [0], [201], [205] | vowel-after | follows-C-tonemark-vabove | = lao semivowel ia; Lao
U+0EC0 | ເ | Lao | LAO VOWEL SIGN E | [0], [201], [205], [206] | vowel-before | precedes-consonant | Lao
U+0EC1 | ແ | Lao | LAO VOWEL SIGN EI | [0], [201], [205], [206] | vowel-before | precedes-consonant | Lao
U+0EC2 | ໂ | Lao | LAO VOWEL SIGN O | [0], [201], [205], [206] | vowel-before | precedes-consonant | Lao
U+0EC3 | ໃ | Lao | LAO VOWEL SIGN AY | [0], [201], [205], [206] | vowel-before | precedes-consonant | Lao
U+0EC4 | ໄ | Lao | LAO VOWEL SIGN AI | [0], [201], [205], [206] | vowel-before | precedes-consonant | Lao
U+0EC6 | ໆ | Lao | LAO KO LA | [0], [203] | sign | repetition-mark-limit | = lao may sam; Lao
U+0EC8 | ່ | Lao | LAO TONE MAI EK | [0], [202] | tone-mark | follows-C-vabove-vbelow | Lao
U+0EC9 | ້ | Lao | LAO TONE MAI THO | [0], [202] | tone-mark | follows-C-vabove-vbelow | Lao
U+0ECA | ໊ | Lao | LAO TONE MAI TI | [0], [202] | tone-mark | follows-C-vabove-vbelow | Lao
U+0ECB | ໋ | Lao | LAO TONE MAI CATAWA | [0], [202] | tone-mark | follows-C-vabove-vbelow | = lao tone mai jattawa; Lao
U+0ECC | ໌ | Lao | LAO CANCELLATION MARK | [0], [207] | sign | follows-Cf | = lao mark mai ka lan; Lao
U+0ECD | ໍ | Lao | LAO NIGGAHITA | [0], [201], [205], [206] | vowel-above | follows-main-consonant | = lao vowel sign or; Lao

Legend

Throughout this LGR, a code point sequence may be annotated with a string in ALL CAPS that is constructed on the same principle as a name for a Unicode Named Sequence. No claim is made that a sequence thus annotated is in fact a named sequence, nor that the annotation in such case actually corresponds to the formal name of a named sequence.

Code Point
  A code point or code point sequence.
Glyph
  The shape displayed depends on the fonts available to your browser.
Script
  Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common. Sequences are annotated with a set of all distinct script values.
Name
  Shows the character or sequence name from the Unicode Character Database. Named sequences are listed with their normative names, for ad-hoc sequences the individual names are shown separated by “+”.
Ref
  Links to the references associated with the code point or sequence, if any.
Tags
  LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view. For sequences, the tags for all member code points are shown for information; sequences as such do not have tags.
Required Context
  Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
Comment
  The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.

# 3 Variant Sets

This LGR does not specify any variants.

# 4 Classes, Rules and Actions

## 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).

Name | Definition | Count | Members or Ranges | Ref | Comment
--- | --- | --- | --- | --- | ---
Cf | Tag=Cf | 14 | {0E81 0E87 0E8A 0E8D 0E94 0E97 0E99-0E9A 0E9F 0EA1 0EA3 0EA5 0EA7 0EAA} |  | Any Lao final consonant
consonant | Tag=consonant | 27 | {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE} |  | Any Lao consonant
semi-consonant | Tag=semi-consonant | 1 | {0EBC} |  | Lao semi-consonant LO
tone-mark | Tag=tone-mark | 4 | {0EC8-0ECB} |  | Any Lao one mark
vowel-above | Tag=vowel-above | 7 | {0EB1 0EB4-0EB7 0EBB 0ECD} |  | Any Lao vowel above
vowel-below | Tag=vowel-below | 2 | {0EB8-0EB9} |  | Any Lao vowel below
implicit | Tag=sign | 2 | {0EC6 0ECC} |  | Any character tagged as sign
implicit | Tag=vowel-after | 3 | {0EB0 0EB2 0EBD} |  | Any character tagged as vowel-after
implicit | Tag=vowel-before | 5 | {0EC0-0EC4} |  | Any character tagged as vowel-before
implicit | Tag=sc:Laoo | 51 | {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE 0EB0-0EB2 0EB4-0EB9 0EBB-0EBD 0EC0-0EC4 0EC6 0EC8-0ECD} |  | Any character tagged as Lao

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 for which there is no named equivalent.

## 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.

Name | Regular Expression | Used as Trigger | Anchor | Used as Context | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
leading-combining-mark | `(start)[[\p{gc=Mn}] ∪ [∅=\p{gc=Mc}]]` | ✔ |  |  |  | Default WLE rule matching labels with leading combining marks ⍟
follows-consonant | `([:consonant:])← ⚓` |  | ✔ | C |  | WLE Rule 1: A semi-consonant must follow a consonant
precedes-consonant | `⚓ →([:consonant:])` |  | ✔ | C |  | WLE Rule 2: A vowel-before precedes a main consonant cluster
follows-main-consonant | `([:consonant:]|[:semi-consonant:])← ⚓` |  | ✔ | C |  | WLE Rule 3: A vowel-above, and vowel-below follow a main consonant C
follows-C-tonemark-vabove | `([:consonant:]|[:semi-consonant:]|[:tone-mark:]|[:vowel-above:])← ⚓` |  | ✔ | C |  | WLE Rule 4: A vowel-after follows a main consonant, tone-mark or vowel-above
consonant-cluster | `[:consonant:]{1,2}[:semi-consonant:]?` |  |  |  |  | Defining consonant cluster for WLE Rule 5
follows-vbefore-consonant-cluster | `(\u0EC0(:consonant-cluster:))← ⚓` |  | ✔ | C |  | WLE Rule 5: The sequence U+0EB2 U+0EB0 (າະ) follows a vowel before, and a consonant cluster
follows-C-vabove-vbelow | `([:consonant:]|[:semi-consonant:]|[:vowel-above:]|[:vowel-below:])← ⚓` |  | ✔ | C |  | WLE Rule 6: A tone-mark follows a main consonant, vowel-above or vowel-below
follows-Cf | `([:Cf:])← ⚓` |  | ✔ | C |  | WLE Rule 7: The sign U+0ECC (໌) can only occur after final consonants
repetition-mark-limit | `⚓ →(\u0EC6{0,2}(end))` |  | ✔ | C |  | WLE Rule 8: The sign U+0EC6 (ໆ) can only occur 0 to 3 times at the end of the label

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.
(: :) - rule reference
  Non-recursive reference to a named rule.
(... | ...) - 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.
*, +, ?, {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 character set
  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).
∅= - empty set
  Indicates that the following set is empty because of the result of set operations, or because none of its elements is part of the repertoire defined here. A rule with a non-optional empty set never matches.
⍟ - default rule
  Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

## 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.

# | Condition | Rule / Variant Set |  | Disposition | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
1 | if label matches | leading-combining-mark | → | invalid |  | labels with leading combining marks are invalid ⍟
2 | if at least one variant is in | {out-of-repertoire-var} | → | invalid |  | any variant label with a code point out of repertoire is invalid ⍟
3 | if at least one variant is in | {blocked} | → | blocked |  | any variant label containing blocked variants is blocked ⍟
4 | if each variant is in | {allocatable} | → | allocatable |  | variant labels with all variants allocatable are allocatable ⍟
5 | 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.

# 5 Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the "References" section in the Description.

[0] | The Unicode Standard 1.1 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 in [Proposal-Lao]
[202] | Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 2 in [Proposal-Lao]
[203] | Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 3 in [Proposal-Lao]
[204] | Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 4 in [Proposal-Lao]
[205] | Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 5 in [Proposal-Lao]
[206] | Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 6 in [Proposal-Lao]
[207] | Lao grammar 1935, see Appendix B, Figure 7 in [Proposal-Lao]