Root Zone LGR for script und-Laoo (Lao)

This document is mechanically formatted from the 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 2017-07-26
LGR Version 2
Language und-Laoo
Scope domain: "." (Root)
Unicode Version 6.3.0


Label Generation Rules for Lao


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].


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.


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:

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].


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:

Integration Panel, "Maximal Starting Repertoire — MSR-2 Overview and Rationale", 14 April 2015
Lao Generation Panel, "Proposal for Lao Script Root Zone LGR",
[RFC 7940]
Davies, K. and A. Freytag, "Representing Label Generation Rulesets Using XML", RFC 7940, August 2016,
[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)

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.



Number of elements in Repertoire 52
Longest code point sequence 2
Number of code points 51
Number of sequences 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.

See also the legend provided below the table.

Glyph Script Name References Tags Required Context Comment
U+0E81 Lao LAO LETTER KO [0], [201], [204] Cf consonant   Lao
U+0E82 Lao LAO LETTER KHO SUNG [0], [201], [204] consonant   Lao
U+0E84 Lao LAO LETTER KHO TAM [0], [201], [204] consonant   Lao
U+0E87 Lao LAO LETTER NGO [0], [201], [204] Cf consonant   Lao
U+0E88 Lao LAO LETTER CO [0], [201], [204] consonant   Lao
U+0E8A Lao LAO LETTER SO TAM [0], [201], [204] Cf consonant   Lao
U+0E8D Lao LAO LETTER NYO [0], [201], [204] Cf consonant   Lao
U+0E94 Lao LAO LETTER DO [0], [201], [204] Cf consonant   Lao
U+0E95 Lao LAO LETTER TO [0], [201], [204] consonant   Lao
U+0E96 Lao LAO LETTER THO SUNG [0], [201], [204] consonant   Lao
U+0E97 Lao LAO LETTER THO TAM [0], [201], [204] Cf consonant   Lao
U+0E99 Lao LAO LETTER NO [0], [201], [204] Cf consonant   Lao
U+0E9A Lao LAO LETTER BO [0], [201], [204] Cf consonant   Lao
U+0E9B Lao LAO LETTER PO [0], [201], [204] consonant   Lao
U+0E9C Lao LAO LETTER PHO SUNG [0], [201], [204] consonant   Lao
U+0E9D Lao LAO LETTER FO TAM [0], [201], [204] consonant   Lao
U+0E9E Lao LAO LETTER PHO TAM [0], [201], [204] consonant   Lao
U+0E9F Lao LAO LETTER FO SUNG [0], [201], [204] Cf consonant   Lao
U+0EA1 Lao LAO LETTER MO [0], [201], [204] Cf consonant   Lao
U+0EA2 Lao LAO LETTER YO [0], [201], [204] consonant   Lao
U+0EA3 Lao LAO LETTER LO LING [0], [204] Cf consonant   Lao
U+0EA5 Lao LAO LETTER LO LOOT [0], [201], [204] Cf consonant   Lao
U+0EA7 Lao LAO LETTER WO [0], [201], [204], [205] Cf consonant   Lao
U+0EAA Lao LAO LETTER SO SUNG [0], [201], [204] Cf consonant   Lao
U+0EAB Lao LAO LETTER HO SUNG [0], [201], [204] consonant   Lao
U+0EAD Lao LAO LETTER O [0], [201], [204], [205] consonant   Lao
U+0EAE Lao LAO LETTER HO TAM [0], [201], [204] consonant   Lao
U+0EB0 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 Lao LAO VOWEL SIGN AA [0], [201], [205], [206] vowel-after follows-C-tonemark-vabove Lao
U+0EB2 U+0EB0 າະ [205]   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
U+0EBD Lao LAO SEMIVOWEL SIGN NYO [0], [201], [205] vowel-after follows-C-tonemark-vabove Lao
U+0EC0 Lao LAO VOWEL SIGN E [0], [201], [205], [206] vowel-before precedes-consonant Lao
U+0EC1 Lao LAO VOWEL SIGN EI [0], [201], [205], [206] vowel-before precedes-consonant Lao
U+0EC2 Lao LAO VOWEL SIGN O [0], [201], [205], [206] vowel-before precedes-consonant Lao
U+0EC3 Lao LAO VOWEL SIGN AY [0], [201], [205], [206] vowel-before precedes-consonant Lao
U+0EC4 Lao LAO VOWEL SIGN AI [0], [201], [205], [206] vowel-before precedes-consonant Lao
U+0EC6 Lao LAO KO LA [0], [203] sign repetition-mark-limit LAO MAY SAM
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 TONE MAI JATTAWA
U+0ECB Lao LAO TONE MAI CATAWA [0], [202] tone-mark follows-C-vabove-vbelow LAO MARK MAI KA LAN
U+0ECD Lao LAO NIGGAHITA [0], [201], [205], [206] vowel-above follows-main-consonant Lao


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.
Shows the character or sequence name from the Unicode Character Database.
The shape displayed depends on the fonts available to your browser.
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 not annotated with a script value.
Links to the references associated with the code point or sequence, if any.
LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view.
Required Context
Link to the rule defining the required context a code point or sequence must satisfy. If prefixed by "not:", identifies a context that must not occur.
If the comment in this row consists only of the code point or sequence name, it is suppressed in this view.

Variant Sets

This LGR does not specify any variants.

Classes, Rules and Actions

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 Elements: {0E81 0E87 0E8A 0E8D 0E94 0E97 0E99-0E9A 0E9F 0EA1 0EA3 0EA5 0EA7 0EAA}    
consonant Tag=consonant 27 Elements: {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE}    
semi-consonant Tag=semi-consonant 1 Elements: {0EBC}    
tone-mark Tag=tone-mark 4 Elements: {0EC8-0ECB}    
vowel-above Tag=vowel-above 7 Elements: {0EB1 0EB4-0EB7 0EBB 0ECD}    
vowel-below Tag=vowel-below 2 Elements: {0EB8-0EB9}    
implicit Tag=vowel-after 3 Elements: {0EB0 0EB2 0EBD}    
implicit Tag=vowel-before 5 Elements: {0EC0-0EC4}    
implicit Tag=sign 2 Elements: {0EC6 0ECC}    
implicit Tag=sc:Laoo 51 Elements: {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE ...}    


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 "...".
A named or implicit class defined by all code points that share the given tag value (ttt).
An anonymous class implicitly defined based on tag value.

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. (Any use of context rules for variants is not indicated).

Name Used as
Used as
Anchor Regular Expression Ref Comment
leading-combining-mark     (^[[\p{gc=Mn}][∅=\p{gc=Mc}]])   Default WLE rule from MSR-2 matching labels with leading combining marks ⍟
follows-consonant   ((?<=[:consonant:])⚓)   WLE Rule 1: A semi-consonant must follow a consonant
precedes-consonant   (⚓(?=[:consonant:]))   WLE Rule 2: A vowel-before precedes a main consonant cluster
follows-main-consonant   ((?<=([:consonant:]|[:semi-consonant:]))⚓)   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:]))⚓)   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:))⚓)   WLE Rule 5: The sequence (0EB2 0EB0) follows a vowel before, and a consonant cluster
follows-C-vabove-vbelow   ((?<=([:consonant:]|[:semi-consonant:]|[:vowel-above:]|[:vowel-below:]))⚓)   WLE Rule 6: A tone-mark follows a main consonant, vowel-above or vowel-below
follows-Cf   ((?<=[:Cf:])⚓)   WLE Rule 7: The sign 0ECC can only occur after final consonants
repetition-mark-limit   (⚓(?=\u0EC6{0,2}$))   WLE Rule 8: The sign 0EC6 can only occur 0 to 3 times at the end of the label


Used as Trigger
This rule triggers one of the actions listed below.
Used as Context
This rule defines a required context for a code point.
This has a placeholder for the code point for which it is evaluated.
Regular Expression
A regular expression equivalent to the rule, shown in the standard notation with some extensions 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.
[: :] - 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
A character set defined by reference to a value for a given Unicode property [\p{prop=val}]. A set defined via "\P" indicates the set complement.
[&&,-,^] - set operators
Sets may be combined by set operators (&& = intersection, - = difference, ^ = symmetric difference) or concatenated (union).
⍟ - default rule
Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.


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) ⍟


{...} - 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.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: out-of-repertoire-var, blocked, allocatable. This is not necessarily an error.

Table of References

[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