This file contains a set of Label Generation Rules (LGR) for the Lao script for the Root Zone. For more details on this LGR and additional 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-6]. The format of this file follows [RFC 7940].
In addition to the 51 code points according to Section 5 “Repertoire” in [Proposal-Lao], the sequence U+0EB2 U+0EB0 has been defined to facilitate implementation of WLE rule follows-vbefore-consonant-cluster as a context rule. The repertoire only includes code points used by languages that are actively written in the Khmer script.
The repertoire is contained in [MSR-6], which is a subset of [Unicode 16.0.0].
As part of the Root Zone, this LGR includes neither decimal digits nor the HYPHEN-MINUS.
Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used and one or more other character categories. For each repertoire element, one or more references document sufficient justification for inclusion in the repertoire; see the “References” below. For code points in the repertoire, comments identify the language using the code point.
According to Section 6, “Variants” in [Proposal-Lao], this LGR defines no variants.
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 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]).
The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-6]. 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. The actions compute a label disposition based on WLE rules or variant mapping types.
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:
No context rules apply to “consonant” code points. For discussion, see Section 5.1, “Consonants” in [Proposal-Lao].
The Root Zone LGR for the Lao Script was developed by the Lao Generation Panel. For details on methodology and contributors, see Sections 4 and 8 in [Proposal-Lao], as well as [RZ-LGR-6-Overview].
The following general references are cited in this document:
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.
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