Root Zone LGR for script: Thai (Thai) | lgr-4-thai-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-Thai
Scope | domain: "." (Root)
Unicode Version | 6.3.0

## Table of Contents

# 1 Description

# Root Zone Label Generation Rules for the Thai Script

## Overview

This file contains Label Generation Rules (LGR) for the Thai 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 Thai Script Root Zone LGR [Proposal-Thai]". 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 68 single code points according to Section 5 “Repertoire” in [Proposal-Thai], three sequences have been defined. The sequence U+0E4D U+0E32 (ํา) was defined to replace the disallowed U+0E33 (SARA AM) and to facilitate implementation of WLE rule follows-consonant-tone as a context rule. The other two sequences were defined to restrict U+0E45 (LAKKHANGYAO) from appearing in any context other than these sequences. Accordingly, while U+0E45 (ๅ) is not listed by itself it brings the total of distinct code points to 69.

The repertoire only includes code points used by languages that are actively written in the Thai 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, and one or more references documenting sufficient justification for inclusion in the repertoire; see "References" below.

## Variants

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

## Character Classes

The Thai Script is an abugida in which consonant–vowel sequences are written as a unit: each unit is based on a consonant letter, and vowel, tone mark or diacritic notation are secondary. It is written with the combining marks stacked above or below the base consonant, like diacritics in European languages. However, although the concepts are quite similar, the implementations are significantly different.

Consonants: There are 44 characters that are classified as consonants; code points from this subset have been given the tag "cons". See Section 5.1, "Consonants" in [Proposal-Thai].

Vowels: The 18 vowel symbols pronounced after a consonant are non-sequential: they can be located before (lv) , after (fv), above (av) or below (bv) the consonant, or in a combination of these positions, code points from this subset have been given the tags "fv1", "fv2", "fv3", "av", "bv", or "lv". There are three code point sequences defined that include vowels. (Code point sequences do not carry tag values; instead, for code point sequences the subset values are identified in comments). See Section 5.2, "Vowels" in [Proposal-Thai].

Tones: There are 5 phonemic tones: mid, low, falling, high, and rising. These 5 tones are represented by 4 tone marks plus the absence of a mark. Code points from this subset have been given the tag "tone". See section 5.3, "Tone Marks" in [Proposal-Thai].

Diacritical Marks: There are 3 diacritic symbols above that have been included here and given the tag "ad". They differ in their frequency and purpose of usage. See also the discussion in Section 5.,4 "Diacritics" in [Proposal-Thai].

- U+0E47 (MAITAIKHU) and U+0E4C (THANTHAKHAT) are commonly used for words in everyday communication
- U+0E4D (NIKHAHIT) is included because of its use to decompose U+0E33 ( ําา ) THAI CHARACTER SARA AM, which is in common use. However, NIKHAHIT may also be used by itself.

A fourth above diacritic, U+0E4E (YAMAKKAN), has been excluded from the Root Zone LGR repertoire because it is rarely used in Modern Thai or even in older Pali manuscripts; it is more common to replace it with U+0E3A (PHINTHU), a below diacritic, which has been given the tag "bd". Moreover, excluding U+0E4E (YAMAKKAN) also eliminates the chance of confusion between U+0E4E (YAMAKKAN) and U+0E4C (THANTHAKHAT). Both look similar, are always placed at the same position in the word cell, and they are normally displayed in a small size.

## 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 ⍟.

### Thai-specific Rules

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

The rules are:

- A leading-vowel must precede a consonant — See Section 7.2 in [Proposal-Thai]
- A below-vowel must follow a consonant — See Section 7.3 in [Proposal-Thai]
- An above-vowel must follow a consonant — See Section 7.3 in [Proposal-Thai]
- A below diacritic must follow a consonant — See Section 7.3 in [Proposal-Thai]
- An above-diacritic MAITAIKHU must follow a consonant — See Section 7.3 in [Proposal-Thai]
- A vowel MAIHAN AKAT must be in between a consonant and either tone or consonant — See Section 7.4 in [Proposal-Thai]
- A vowel SARA A can follow a consonant, a tone or a vowel SARA AA — See Section 7.5 in [Proposal-Thai]
- A vowel SARA AA, or an above diacritic NIKHAHIT followed by a vowel SARA AA can follow a consonant or a tone — See Sections 7.6 and 7.9 in [Proposal-Thai]
- A tone-mark, THANTHAKHAT, NIKHAHIT can only follow a consonant, above-vowel or below-vowel — See section 7.7 and 7.8 in [Proposal-Thai]

## Methodology and Contributors

The Root Zone LGR for the Thai script was developed by the Thai Generation Panel. For methodology and contributors, see Sections 4 and 8 in [Proposal-Thai], 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-Thai]
  Proposal for a Thai Script Root Zone LGR, 25 May 2017,
  https://www.icann.org/en/system/files/files/proposal-thai-lgr-25may17-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 Thai script for the Root Zone 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 [100] and [101] correspond to sources given in [Proposal-Thai] for justifying the inclusion of for the corresponding code points. Entries in the table may have multiple source reference values.

# 2 Repertoire

## Repertoire Summary

Number of elements in repertoire | 71
Number of code points | 68
Number of sequences | 3
Longest code point sequence | 2
Code points defined via sequence | 1

## 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.

Some code points that may be part of a valid label under this LGR only occur as part of one or more sequences. Such code points are not listed individually in the table.

See also the legend provided below the table.

Code Point | Glyph | Script | Name | Ref | Tags | Required Context | Comment
--- | --- | --- | --- | --- | --- | --- | ---
U+0E01 | ก | Thai | THAI CHARACTER KO KAI | [0], [100], [101] | cons |  | Thai
U+0E02 | ข | Thai | THAI CHARACTER KHO KHAI | [0], [100], [101] | cons |  | Thai
U+0E03 | ฃ | Thai | THAI CHARACTER KHO KHUAT | [0], [100], [101] | cons |  | Thai
U+0E04 | ค | Thai | THAI CHARACTER KHO KHWAI | [0], [100], [101] | cons |  | Thai
U+0E05 | ฅ | Thai | THAI CHARACTER KHO KHON | [0], [100], [101] | cons |  | Thai
U+0E06 | ฆ | Thai | THAI CHARACTER KHO RAKHANG | [0], [100], [101] | cons |  | Thai
U+0E07 | ง | Thai | THAI CHARACTER NGO NGU | [0], [100], [101] | cons |  | Thai
U+0E08 | จ | Thai | THAI CHARACTER CHO CHAN | [0], [100], [101] | cons |  | Thai
U+0E09 | ฉ | Thai | THAI CHARACTER CHO CHING | [0], [100], [101] | cons |  | Thai
U+0E0A | ช | Thai | THAI CHARACTER CHO CHANG | [0], [100], [101] | cons |  | Thai
U+0E0B | ซ | Thai | THAI CHARACTER SO SO | [0], [100], [101] | cons |  | Thai
U+0E0C | ฌ | Thai | THAI CHARACTER CHO CHOE | [0], [100], [101] | cons |  | Thai
U+0E0D | ญ | Thai | THAI CHARACTER YO YING | [0], [100], [101] | cons |  | Thai
U+0E0E | ฎ | Thai | THAI CHARACTER DO CHADA | [0], [100], [101] | cons |  | Thai
U+0E0F | ฏ | Thai | THAI CHARACTER TO PATAK | [0], [100], [101] | cons |  | Thai
U+0E10 | ฐ | Thai | THAI CHARACTER THO THAN | [0], [100], [101] | cons |  | Thai
U+0E11 | ฑ | Thai | THAI CHARACTER THO NANGMONTHO | [0], [100], [101] | cons |  | Thai
U+0E12 | ฒ | Thai | THAI CHARACTER THO PHUTHAO | [0], [100], [101] | cons |  | Thai
U+0E13 | ณ | Thai | THAI CHARACTER NO NEN | [0], [100], [101] | cons |  | Thai
U+0E14 | ด | Thai | THAI CHARACTER DO DEK | [0], [100], [101] | cons |  | Thai
U+0E15 | ต | Thai | THAI CHARACTER TO TAO | [0], [100], [101] | cons |  | Thai
U+0E16 | ถ | Thai | THAI CHARACTER THO THUNG | [0], [100], [101] | cons |  | Thai
U+0E17 | ท | Thai | THAI CHARACTER THO THAHAN | [0], [100], [101] | cons |  | Thai
U+0E18 | ธ | Thai | THAI CHARACTER THO THONG | [0], [100], [101] | cons |  | Thai
U+0E19 | น | Thai | THAI CHARACTER NO NU | [0], [100], [101] | cons |  | Thai
U+0E1A | บ | Thai | THAI CHARACTER BO BAIMAI | [0], [100], [101] | cons |  | Thai
U+0E1B | ป | Thai | THAI CHARACTER PO PLA | [0], [100], [101] | cons |  | Thai
U+0E1C | ผ | Thai | THAI CHARACTER PHO PHUNG | [0], [100], [101] | cons |  | Thai
U+0E1D | ฝ | Thai | THAI CHARACTER FO FA | [0], [100], [101] | cons |  | Thai
U+0E1E | พ | Thai | THAI CHARACTER PHO PHAN | [0], [100], [101] | cons |  | Thai
U+0E1F | ฟ | Thai | THAI CHARACTER FO FAN | [0], [100], [101] | cons |  | Thai
U+0E20 | ภ | Thai | THAI CHARACTER PHO SAMPHAO | [0], [100], [101] | cons |  | Thai
U+0E21 | ม | Thai | THAI CHARACTER MO MA | [0], [100], [101] | cons |  | Thai
U+0E22 | ย | Thai | THAI CHARACTER YO YAK | [0], [100], [101] | cons |  | Thai
U+0E23 | ร | Thai | THAI CHARACTER RO RUA | [0], [100], [101] | cons |  | Thai
U+0E24 | ฤ | Thai | THAI CHARACTER RU | [0], [100], [101] | fv3 |  | Thai
U+0E24 U+0E45 | ฤๅ | {Thai} | THAI CHARACTER RU + THAI CHARACTER LAKKHANGYAO | [0], [100], [101] | [fv3] + [] |  | fv2, Thai
U+0E25 | ล | Thai | THAI CHARACTER LO LING | [0], [100], [101] | cons |  | Thai
U+0E26 | ฦ | Thai | THAI CHARACTER LU | [0], [100], [101] | fv3 |  | Thai
U+0E26 U+0E45 | ฦๅ | {Thai} | THAI CHARACTER LU + THAI CHARACTER LAKKHANGYAO | [0], [100], [101] | [fv3] + [] |  | fv2, Thai
U+0E27 | ว | Thai | THAI CHARACTER WO WAEN | [0], [100], [101] | cons |  | Thai
U+0E28 | ศ | Thai | THAI CHARACTER SO SALA | [0], [100], [101] | cons |  | Thai
U+0E29 | ษ | Thai | THAI CHARACTER SO RUSI | [0], [100], [101] | cons |  | Thai
U+0E2A | ส | Thai | THAI CHARACTER SO SUA | [0], [100], [101] | cons |  | Thai
U+0E2B | ห | Thai | THAI CHARACTER HO HIP | [0], [100], [101] | cons |  | Thai
U+0E2C | ฬ | Thai | THAI CHARACTER LO CHULA | [0], [100], [101] | cons |  | Thai
U+0E2D | อ | Thai | THAI CHARACTER O ANG | [0], [100], [101] | cons |  | Thai
U+0E2E | ฮ | Thai | THAI CHARACTER HO NOKHUK | [0], [100], [101] | cons |  | Thai
U+0E30 | ะ | Thai | THAI CHARACTER SARA A | [0], [100], [101] | fv1 | follow-consonant-tone-sara-aa | Thai
U+0E31 | ั | Thai | THAI CHARACTER MAI HAN-AKAT | [0], [100], [101] | av | between-consonant-and-ct | Thai
U+0E32 | า | Thai | THAI CHARACTER SARA AA | [0], [100], [101] | fv1, sara-aa | follows-consonant-tone | Thai
U+0E34 | ิ | Thai | THAI CHARACTER SARA I | [0], [100], [101] | av | follows-consonant | Thai
U+0E35 | ี | Thai | THAI CHARACTER SARA II | [0], [100], [101] | av | follows-consonant | Thai
U+0E36 | ึ | Thai | THAI CHARACTER SARA UE | [0], [100], [101] | av | follows-consonant | Thai
U+0E37 | ื | Thai | THAI CHARACTER SARA UEE | [0], [100], [101] | av | follows-consonant | Thai
U+0E38 | ุ | Thai | THAI CHARACTER SARA U | [0], [100], [101] | bv | follows-consonant | Thai
U+0E39 | ู | Thai | THAI CHARACTER SARA UU | [0], [100], [101] | bv | follows-consonant | Thai
U+0E3A | ฺ | Thai | THAI CHARACTER PHINTHU | [0], [100], [101] | bd | follows-consonant | = phinthu; Thai
U+0E40 | เ | Thai | THAI CHARACTER SARA E | [0], [100], [101] | lv | precedes-consonant | Thai
U+0E41 | แ | Thai | THAI CHARACTER SARA AE | [0], [100], [101] | lv | precedes-consonant | Thai
U+0E42 | โ | Thai | THAI CHARACTER SARA O | [0], [100], [101] | lv | precedes-consonant | Thai
U+0E43 | ใ | Thai | THAI CHARACTER SARA AI MAIMUAN | [0], [100], [101] | lv | precedes-consonant | Thai
U+0E44 | ไ | Thai | THAI CHARACTER SARA AI MAIMALAI | [0], [100], [101] | lv | precedes-consonant | Thai
U+0E47 | ็ | Thai | THAI CHARACTER MAITAIKHU | [0], [100], [101] | ad | follows-consonant | = maitaikhu; Thai
U+0E48 | ่ | Thai | THAI CHARACTER MAI EK | [0], [100], [101] | tone | follows-consonant-av-bv | Thai
U+0E49 | ้ | Thai | THAI CHARACTER MAI THO | [0], [100], [101] | tone | follows-consonant-av-bv | Thai
U+0E4A | ๊ | Thai | THAI CHARACTER MAI TRI | [0], [100], [101] | tone | follows-consonant-av-bv | Thai
U+0E4B | ๋ | Thai | THAI CHARACTER MAI CHATTAWA | [0], [100], [101] | tone | follows-consonant-av-bv | Thai
U+0E4C | ์ | Thai | THAI CHARACTER THANTHAKHAT | [0], [100], [101] | ad | follows-consonant-av-bv | = thanthakhat; Thai
U+0E4D | ํ | Thai | THAI CHARACTER NIKHAHIT | [0], [100], [101] | ad | follows-consonant-av-bv | = nikhahit; Thai
U+0E4D U+0E32 | ํา | {Thai} | THAI CHARACTER NIKHAHIT + THAI CHARACTER SARA AA | [0], [100], [101] | [ad] + [fv1, sara-aa] | follows-consonant-tone | = sara am sequence; Thai

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
--- | --- | --- | --- | --- | ---
above-vowel | Tag=av | 5 | {0E31 0E34-0E37} |  | Any Thai above vowel
below-vowel | Tag=bv | 2 | {0E38-0E39} |  | Any Thai below vowel
consonant | Tag=cons | 44 | {0E01-0E23 0E25 0E27-0E2E} |  | Any Thai consonant
sara-aa | Tag=sara-aa | 1 | {0E32} |  | Thai SARA AA
tone | Tag=tone | 4 | {0E48-0E4B} |  | Any Thai tone mark
c-av-bv | combined = [[:consonant:] ∪ [:above-vowel:] ∪ [:below-vowel:]] | 51 | {0E01-0E23 0E25 0E27-0E2E 0E31 0E34-0E39} |  | Any Thai consonant, vowel-above or vowel-below
ct | combined = [[:consonant:] ∪ [:tone:]] | 48 | {0E01-0E23 0E25 0E27-0E2E 0E48-0E4B} |  | Any Thai consonant or tone mark
ctaa | combined = [[:consonant:] ∪ [:tone:] ∪ [:sara-aa:]] | 49 | {0E01-0E23 0E25 0E27-0E2E 0E32 0E48-0E4B} |  | Any Thai consonant, tone or sara-aa
implicit | Tag=ad | 3 | {0E47 0E4C-0E4D} |  | Any character tagged as ad
implicit | Tag=bd | 1 | {0E3A} |  | The character tagged as bd
implicit | Tag=fv1 | 2 | {0E30 0E32} |  | Any character tagged as fv1
implicit | Tag=fv3 | 2 | {0E24 0E26} |  | Any character tagged as fv3
implicit | Tag=lv | 5 | {0E40-0E44} |  | Any character tagged as lv
implicit | Tag=sc:Thai | 68 | {0E01-0E2E 0E30-0E32 0E34-0E3A 0E40-0E44 0E47-0E4D} |  | Any character tagged as Thai

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.
Combined
  A named class defined by set operations on other classes using the following syntax:
[: :] - 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.
∪, ∩, ∖, ∆ - set operators
  Sets may be combined by set operators (∪ = union, ∩ = intersection, ∖ = difference, ∆ = symmetric difference).

## 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 ⍟
precedes-consonant | `⚓ →([:consonant:])` |  | ✔ | C |  | WLE 7.2: check if current cp is preceding a consonant
follows-consonant | `([:consonant:])← ⚓` |  | ✔ | C |  | WLE 7.3: check if current cp is following a consonant
between-consonant-and-ct | `([:consonant:])← ⚓ →([:ct:])` |  | ✔ | C |  | WLE 7.4: check if current cp is in between a consonant and either tone or consonant
follow-consonant-tone-sara-aa | `([:ctaa:])← ⚓` |  | ✔ | C |  | WLE 7.5: U+0E30 (THAI CHARACTER SARA A, ะ) can follow a consonant, a tone or U+0E32 (THAI CHARACTER SARA AA, า)
follows-consonant-tone | `([:ct:])← ⚓` |  | ✔ | C |  | WLE 7.6, 7.9: check if current cp is following a consonant or a tone
follows-consonant-av-bv | `([:c-av-bv:])← ⚓` |  | ✔ | C |  | WLE 7.7, 7.8: A tone-mark, THANTHAKHAT, NIKAHIT can only follow a consonant, above-vowel or below-vowel

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.
start or end
  (start) matches the start of the label; (end) matches the end of the label.
[: :] - 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
[100] | Thai Industrial Standard (TIS) 1566-2541(1988) http://www.ratchakitcha.soc.go.th/DATA/PDF/2542/E/088/9.PDF
[101] | Computers and the Thai Language https://lexitron.nectec.or.th/KM_HL5001/file_HL5001/Paper/Inter%20Journal/krrn_52085.pdf