Root Zone Label Generation Rules for the Malayalam Script

Overview

This file contains Label Generation Rules (LGR) for the Malayalam script for the Root zone. For more details on this LGR and its development, see "Proposal for a Malayalam Script Root Zone Label Generation Ruleset (LGR) [Proposal]". The format of this file follows [RFC 7940].

Repertoire

According to Section 5, "Repertoire" in [Proposal], the Malayalam LGR contains 70 unique code points. This LGR caters to the Malayalam language written using the Malayalam script.

The repertoire is based on [MSR-4], which is a subset of [Unicode 6.3].

Code points outside the Malayalam script that are listed in this file are targets for out-of-script variants and are identified by a reflexive (identity) variant of type "out-of-repertoire-var". They do not form part of the repertoire.

Each code point is tagged with the script or scripts that the code point is used with, a category value, and one or more references documenting sufficient justification for inclusion in the repertoire, see "References" below. For code points that are part of the repertoire, comments identify the languages using the code point.

Variants

According to Section 6, "Variants", in [Proposal], this LGR defines one in-script variant due to the multiple ways to write the conjunct “nta" in Malayalam.

This LGR also defines the cross-script variants which are "Confusing due to deviation from normally perceived character formations by larger linguistic community". These cases are not of mere visual similarity; they can cause confusion even to a careful observer and hence have been defined as variants.

Variant Disposition: All variants are of type "blocked", making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated any other equivalent label should be blocked. There is no preference among these variants.

This LGR does not define allocatable variants.

Context Rules for Variants: some of the variants defined in this LGR are "effective null variants", that is, some code points in the source map to "nothing" in the target with all other code points unchanged. (Because mappings are symmetric, it does not matter whether it is the forward or reverse mapping that maps to "null"). Such variants require a context rule to keep the variant set well behaved. Symmetry requires the same context rule for both forward and reverse mappings.

In other cases, the sequences or code points making up source and target are constrained by explicit context rules on the code points (or by implicit context rules defined for the adjacent code points). In such a case, any variants may require context rules that match the intersection between the effective contexts for both source and target; otherwise, a sequence might be considered valid in some variant label when it would not be valid in an equivalent context in an original label.

Some of the sequences defined for Malayalam have the effect of allowing code points in contexts that are otherwise forbidden: context rules are never evaluated between elements of the same sequence.

The specification of variants in the Root Zone LGR follows the guidelines in [RFC 8228].

Character Classes

The basic characters in Malayalam are classified into seven main categories. They are Consonants, Vowels, Matra, Halant, Visargam, Anusvaram and Chillu letters.

Consonants: Malayalam is written in an abugida script derived ultimately from Brāhmī in which every consonant carries an inherent a. More details in Section 3.8, "The Structure of Malayalam Script" of the [Proposal].

Vowels and Matras: Vowels other than the inherent vowel are written as vowel diacritics. They are referred to as Matras, when they follow consonants. When they occur independently they are written with one of 13 independent vowels. More details in Section 3.8, "The Structure of Malayalam Script" of the [Proposal].

Halant: A consonant can be combined with another consonant or conjunct using the halant encoded as U+0D4D (്) MALAYALAM SIGN VIRAMA. This strips off the implicit vowel. More details in Section 3.8, "The Structure of Malayalam Script" of the [Proposal].

Anusvaram: In Malayalam, Anusvara, endoded as U+0D02 (ം), simply represents a consonant /m/ after a vowel, though this /m/ may be assimilated to another nasal consonant. More details in Section 3.8 "The Structure of Malayalam Script" of the [Proposal].

Visargam: Visargam or Visarga, encoded as U+0D03 (ഃ), represents a consonant /h/ after a vowel, and is transliterated as ḥ. Like the anusvara, it is a special symbol, and is never followed by an inherent vowel or another vowel. More details in Section 3.8, "The Structure of Malayalam Script" of the [Proposal].

Chillus: Chillu letters, aka "Chillaksharam", represent pure consonants without any vowel sound. More details in Section 3.8, "The Structure of Malayalam Script" of the [Proposal].

Reordrant: Vowel diacritics, part of which reorder around the preceding character or conjunct More details in Sections 6.1 "In-script Variants" and 7.1.1 "Variables or definitions" of the [Proposal].

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.

Malayalam-specific Rules and Action

The Malayalam LGR speficies a number of context rules that constrain possible labels so that they reasonably conform to Malayalam syllable structure An additional whole-label rule and associated action enforce the restriction that a label may not begin with a chillu.

The following symbols are used in the WLE rules:
C → Consonant
M → Matra
V → Vowel
B → Anusvara
X → Visarga
D → Chandrabindu
H → Halant
L → Chillu
R → Reordrant Matra

Note: the Reordrant Matras include one sequence. That requires an auxiliary rule R in addition to class R.

The rules are:

• 1. H: must be preceded by C or U+0D41 (ു) or U+07DB (ߛ)
• 2. M: must be preceded by C
• 3. B: must be preceded by C, V or M
• 4. X: must be preceded by C, V or M
• 5. L: cannot be preceded by B, X or H
• 6. A label does not begin with L

The following context rules apply to code points U+0D33 (ള) and U+0D31 (റ) as well as to sequences ending in these code points:

• 7. The character U+0D33 (ള) cannot immediately follow U+0D33 (ള), except as part of a defined sequence
• 8. The character U+0D31 (റ) cannot immediately follow U+0D31 (റ), except as part of a defined sequence

The following context rules apply to variants:

• V1: A variant preceded by 0D33+Halant or followed by R or Halant+0D33 is not defined
• V2: A variant preceded by 0D31+Halant or followed by R of Halant+0D31 is not defined

More details in Section 6.1 "In-script Variants" and Section 7, "Whole Label Evaluation Rules (WLE)" of the [Proposal].

Note: the implementation of Rules 7 & 8 relies on the fact that a context rule is not evaluated between code points in the same sequence. For example, if a label contains two adjacent U+0D33 U+0D33 (ളള) surrounded by other code points, the two code points can only be interpreted as the sequence U+0D33 U+0D33 (ളള) because a singleton U+0D33 (ള) is not allowed to be followed by another U+0D33 (ള).

Methodology and Contributors

The LGR for the Malayalam script was developed by the Neo-Brahmi Generation Panel (NBGP) the members of which have experience in linguistics and computational linguistics in a wide variety of languages written with Neo-Brahmi scripts. Under the Neo-Brahmi Generation Panel, there are nine scripts belonging to separate Unicode blocks. Each of these scripts has been assigned a separate LGR, with the Neo-Brahmi GP ensuring that the fundamental philosophy behind building each LGR is in sync with all other Brahmi derived scripts. For further details on methodology and contributors, see Sections 4 and 8 of [Proposal].

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]

Neo-Brahmi Generation Panel, "Proposal for a Malayalam Script Root Zone Label Generation Ruleset (LGR)", 22 April 2019,
https://www.icann.org/en/system/files/files/proposal-malayalam-lgr-22apr19-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.

[RFC 8228]

A. Freytag, "Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels", RFC 8228, August 2017,
https://www.rfc-editor.org/info/rfc8228

[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/

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).

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.

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.