Root Zone LGR for script und-Taml (Tamil) lgr-3-tamil-script-10jul19-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 2019-07-10
LGR Version 3
Language und-Taml
Scope domain: "." (Root)
Unicode Version 6.3.0

Table of Contents

1 Description

Root Zone Label Generation Rules for the Tamil Script


This file contains Label Generation Rules (LGR) for the Tamil script for the Root zone. For more details on this LGR and its development, see "Proposal for a Tamil Script Root Zone Label Generation Rule-Set (LGR)" [Proposal]. This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-3]. The format of this file follows [RFC 7940].


According to Section 5, "Repertoire" in [Proposal] the Tamil LGR contains 48 unique code points and 4 sequences. This LGR caters to the Tamil language written using Tamil script.

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

Code points outside the Tamil 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. Comments provide alternate names for some code points.


According to Section 6, "Variants", in [Proposal], this LGR defines four sequences as in-script variants. Two of them are variants to single code points; the other two are variants of each other; all defined variants look exactly alike and can cause confusion even to a careful observer.

In addition to these, this LGR defines 6 cross-script variants with the Malayalam script.

Variant Disposition: Except as noted, 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, while any other equivalent label should be blocked.

For historical reasons, there are two sequences that both represent the same akshar (Shri) with exactly the same rendered form. These two sequences are thus semantically identical and users may choose either one, except that a single label must use one of these forms consistently. This variant pair is thus being defined as "allocatable" variant. (For more details see Section 6.1 in [Proposal].)

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

Character Classes

Tamil is an alphasyllabary and the heart of the writing system is the Akshar. This is the unit which is instinctively recognized by users of the script. The writing system of Tamil could be summed up as composed of Consonants, the Implicit Vowel Killer: Halant, Vowels and Visarga/Aytham.

Consonants: More details in Section 3.3.1, "The Consonants" in [Proposal].

Halant / Virama: All consonants contain an implicit vowel (a). A special sign is needed to denote that this implicit vowel is stripped off. This is known as the Pulli and encoded as U+0BCD ( ் ) TAMIL SIGN VIRAMA. The virama thus joins two adjacent consonants. In Tamil, there are only two cases where this forms conjuncts. More details in Section 3.3.2, "Virama/Pulli" of the [Proposal].

Vowels and Matras: Separate symbols exist for all Vowels that are pronounced independently either at the beginning or after another vowel sound. To indicate a Vowel sound other than the implicit one following a consonant, a Vowel sign (matra) is attached to the consonant. Since the consonant has a built in ‘a’, there are equivalent Matras for all vowels excepting the அ. More details in Section 3.3.3, "Vowels" in [Proposal].

Visarga: The Visarga (or Aytham) is used in Tamil to represent a sound very close to /ḵ/. More details in Section 3.3.4, "Visarga/Aytham" in [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.

Tamil-specific Rules and Action

These rules have been drafted to ensure that the prospective Tamil label conforms to akshar formation norms as desired in Tamil script. These norms are exclusively presented as context rules.

The following symbols are used in the WLE rules:
C → Consonant
M → Matra
H → Haleant /V irama =Pulli
X → Visarga = Aytham

The rules are:

  1. H: must be preceded by C
  2. M: must be preceded by C
  3. X: cannot be preceded by X

The following whole-label rule and associated action prevent the mixing of two allocatable variants of the same sequence within the same label. This reduces overproduction of variant labels.

  1. Two representations of 'Shri' cannot be mixed in the same label

More details in Section 7 "Whole Label Evaluation Rules (WLE)" in [Proposal].

Methodology and Contributors

The LGR for the Tamil 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 in [Proposal], as well as [RZ-LGR-3-Overview].


The following general references are cited in this document:

Integration Panel, "Maximal Starting Repertoire — MSR-4 Overview and Rationale", 7 February 2019,
Neo-Brahmi Generation Panel, "Proposal for a Tamil Script Root Zone Label Generation Rule-Set (LGR)", 6 March 2019,
[RFC 7940]
Davies, K. and A. Freytag, "Representing Label Generation Rulesets Using XML", RFC 7940, August 2016,
[RFC 8228]
A. Freytag, "Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels", RFC 8228, August 2017,
Integration Panel, "Root Zone Label Generation Rules - LGR-3: Overview and Summary", 10 July 2019 (PDF),
Integration Panel, "Label Generation Rules for the Root Zone — LGR-3", 10 July 2019 (XML),
non-normative HTML presentation:
[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)

2 Repertoire

Repertoire Summary

Number of elements in Repertoire 52
Out of repertoire variants 6
Total entries in table 58
Number of code points
for each script
Malayalam 6
Tamil 48
Number of code points 54
Number of sequences 4
Longest code point sequence 4

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.

For any code point or sequence for which a variant is defined, additional information is provided in the Variants column. Some code points or sequences listed in the following table are not part of the repertoire itself; they document targets for out-of-repertoire variant mappings as indicated. See also the legend provided below the table.

Glyph Script Name Ref Tags Required Context Part of
Variants Comment
U+0B83 Tamil TAMIL SIGN VISARGA [1003] Visarga not: preceded-by-X   = aytham
U+0B85 Tamil TAMIL LETTER A [1001] Vowel      
U+0B86 Tamil TAMIL LETTER AA [1001] Vowel      
U+0B87 Tamil TAMIL LETTER I [1001] Vowel      
U+0B88 Tamil TAMIL LETTER II [1001] Vowel      
U+0B89 Tamil TAMIL LETTER U [1001] Vowel      
U+0B8A Tamil TAMIL LETTER UU [1001] Vowel      
U+0B8E Tamil TAMIL LETTER E [1001] Vowel      
U+0B8F Tamil TAMIL LETTER EE [1001] Vowel      
U+0B90 Tamil TAMIL LETTER AI [1001] Vowel      
U+0B92 Tamil TAMIL LETTER O [1001] Vowel      
U+0B92 U+0BB3 ஒள [Tamil] TAMIL LETTER O + TAMIL LETTER LLA       set 1 homoglyph of U+0B94 (ஔ)
U+0B93 Tamil TAMIL LETTER OO [1001] Vowel      
U+0B94 Tamil TAMIL LETTER AU [1001] Vowel   set 1  
U+0B95 Tamil TAMIL LETTER KA [1002] Consonant      
U+0B99 Tamil TAMIL LETTER NGA [1002] Consonant      
U+0B9A Tamil TAMIL LETTER CA [1002] Consonant      
U+0B9C Tamil TAMIL LETTER JA [1002] Consonant   set 2  
U+0B9E Tamil TAMIL LETTER NYA [1002] Consonant      
U+0B9F Tamil TAMIL LETTER TTA [1002] Consonant      
U+0BA3 Tamil TAMIL LETTER NNA [1002] Consonant      
U+0BA4 Tamil TAMIL LETTER TA [1002] Consonant      
U+0BA8 Tamil TAMIL LETTER NA [1002] Consonant      
U+0BA9 Tamil TAMIL LETTER NNNA [1002] Consonant      
U+0BAA Tamil TAMIL LETTER PA [1002] Consonant      
U+0BAE Tamil TAMIL LETTER MA [1002] Consonant   set 3  
U+0BAF Tamil TAMIL LETTER YA [1002] Consonant      
U+0BB0 Tamil TAMIL LETTER RA [1002] Consonant      
U+0BB1 Tamil TAMIL LETTER RRA [1002] Consonant      
U+0BB2 Tamil TAMIL LETTER LA [1002] Consonant      
U+0BB3 Tamil TAMIL LETTER LLA [1002] Consonant      
U+0BB4 Tamil TAMIL LETTER LLLA [1002] Consonant      
U+0BB5 Tamil TAMIL LETTER VA [1002] Consonant   set 4  
U+0BB6 Tamil TAMIL LETTER SHA [1002] Consonant      
U+0BB6 U+0BCD U+0BB0 U+0BC0 ஶ்ரீ [Tamil] TAMIL SYLLABLE SHRII       set 5  
U+0BB7 Tamil TAMIL LETTER SSA [1002] Consonant      
U+0BB8 Tamil TAMIL LETTER SA [1002] Consonant      
U+0BB9 Tamil TAMIL LETTER HA [1002] Consonant      
U+0BBE Tamil TAMIL VOWEL SIGN AA [1002] Matra follows-C    
U+0BBF ி Tamil TAMIL VOWEL SIGN I [1002] Matra follows-C set 6  
U+0BC0 Tamil TAMIL VOWEL SIGN II [1002] Matra follows-C    
U+0BC1 Tamil TAMIL VOWEL SIGN U [1002] Matra follows-C    
U+0BC2 Tamil TAMIL VOWEL SIGN UU [1002] Matra follows-C    
U+0BC6 Tamil TAMIL VOWEL SIGN E [1002] Matra follows-C set 7  
U+0BC6 U+0BB3 ெள [Tamil] TAMIL VOWEL SIGN E + TAMIL LETTER LLA     follows-C set 8 homoglyph of U+0BCC (ௌ)
U+0BC7 Tamil TAMIL VOWEL SIGN EE [1002] Matra follows-C set 9  
U+0BC8 Tamil TAMIL VOWEL SIGN AI [1002] Matra follows-C    
U+0BCA Tamil TAMIL VOWEL SIGN O [1002] Matra follows-C    
U+0BCB Tamil TAMIL VOWEL SIGN OO [1002] Matra follows-C    
U+0BCC Tamil TAMIL VOWEL SIGN AU [1002] Matra follows-C set 8  
U+0BCD Tamil TAMIL SIGN VIRAMA [1002] Halant follows-C   = pulli
U+0D16 Malayalam MALAYALAM LETTER KHA       set 4 Not part of repertoire
U+0D1C Malayalam MALAYALAM LETTER JA       set 2 Not part of repertoire
U+0D25 Malayalam MALAYALAM LETTER THA       set 3 Not part of repertoire
U+0D3F ി Malayalam MALAYALAM VOWEL SIGN I       set 6 Not part of repertoire
U+0D46 Malayalam MALAYALAM VOWEL SIGN E       set 7 Not part of repertoire
U+0D47 Malayalam MALAYALAM VOWEL SIGN EE       set 9 Not part of repertoire


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. Named sequences are listed with their normative names, for ad-hoc sequences the individual names are shown separated by “+”.
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 annotated with a set of all distinct script values.
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 a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:ℍ identifies a context that must not occur.
Link to the variant set the code point or sequence is a member of, except where a coded point or sequence maps only to itself, in which case the type of that mapping is listed.
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.
✔ - core repertoire
A check mark in the Part-of-Repertoire column indicates a code point is part of the core repertoire.
✗ - out-of-repertoire
A code point shown with is not part of the repertoire. It is listed only because it is the target of an out-of-repertoire-var variant mapping.

3 Variant Sets

Variant Set Summary

Number of variant sets 9
Largest variant set 2
Ordinary Variants by Type
allocatable 2
blocked 16
Reflexive Variants by Type
out-of-repertoire-var 6

The following tables list all variant sets defined in this LGR, except for singleton sets. Each table lists all variant mapping pairs of the set; one per row. Mappings are assumed to be symmetric: each row documents both forward (→) and reverse (←) mapping directions. In each table, the mappings are sorted by Source value in ascending code point order; shading is used to group mappings from the same source code point or sequence.

Where the type of both forward and reverse mappings are the same, a single value is given in the Type column, otherwise the types for forward and reverse mappings, as well as comments and references are listed above one another. For summary counts, both forward and reverse mappings are always counted separately.

A mapping where source and target are the same is reflexive. Variant sets consisting of only a single reflexive mapping are not shown as a set. Instead, the variant type of the mapping is listed in the Variants column of the Repertoire by Code Point table. Reflexive mappings that are part of a larger set are indicated with a “≡” and are counted once per entry.

In any LGR with variant specifications that are well behaved, all members within each variant set are defined as variants of each other; the mappings in each set are symmetric and transitive; and all variant sets are disjoint.

Common Legend

By convention, the smaller of the two code points in a variant mapping pair.
By convention, the larger of the two code points in a variant mapping pair.
The shape displayed for source or target depends on the fonts available to your browser.
- forward
Indicates that Type, Ref and Comment apply to the mapping from source to target.
- reverse
Indicates that Type, Ref and Comment apply to the reverse mapping from target to source.
- both
Indicates that Type, Ref and Comment apply to both forward and reverse mapping.
- reflexive
Indicates that Type, Ref and Comment are for a reflexive mapping where source equals target.
The type of the variant mapping. There are some predefined variant types such as “allocatable” and “blocked”, while others are defined specifically for each LGR. A reflexive variant type “out-of-repertoire-var” designates the target as not part of the repertoire; it is required as target for one or more variant mappings that cross repertoire boundaries.
One or more reference IDs (optional). A “/” separates references for reverse / forward mappings, if different.
A descriptive comment (optional). A “/” separates comments for reverse / forward mappings, if different.

Variant Set 1 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0B92 0BB3 ஒள 0B94 blocked   Tamil homoglyph / homoglyph

Variant Set 2 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0B9C 0D1C blocked   Cross-script homoglyph
0D1C 0D1C out-of-repertoire-var   Out-of-repertoire

Variant Set 3 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BAE 0D25 blocked   Cross-script homoglyph
0D25 0D25 out-of-repertoire-var   Out-of-repertoire

Variant Set 4 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BB5 0D16 blocked   Cross-script homoglyph
0D16 0D16 out-of-repertoire-var   Out-of-repertoire

Variant Set 5 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BB6 0BCD 0BB0 0BC0 ஶ்ரீ 0BB8 0BCD 0BB0 0BC0 ஸ்ரீ allocatable   Alternate for Tamil SHRII

Variant Set 6 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BBF ி 0D3F ി blocked   Cross-script homoglyph
0D3F ി 0D3F ി out-of-repertoire-var   Out-of-repertoire

Variant Set 7 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BC6 0D46 blocked   Cross-script homoglyph
0D46 0D46 out-of-repertoire-var   Out-of-repertoire

Variant Set 8 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BC6 0BB3 ெள 0BCC blocked   homoglyph / Tamil Homoglyph

Variant Set 9 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BC7 0D47 blocked   Cross-script homoglyph
0D47 0D47 out-of-repertoire-var   Out-of-repertoire

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
C Tag=Consonant 23 {0B95 0B99-0B9A 0B9C 0B9E-0B9F 0BA3-0BA4 0BA8-0BAA 0BAE-0BB9}   Any Tamil consonant
X Tag=Visarga 1 {0B83}   The Tamil Visarga (aytham)
implicit Tag=Halant 1 {0BCD}   The character tagged as Halant
implicit Tag=Matra 11 {0BBE-0BC2 0BC6-0BC8 0BCA-0BCC}   Any character tagged as Matra
implicit Tag=Vowel 12 {0B85-0B8A 0B8E-0B90 0B92-0B94}   Any character tagged as Vowel
implicit Tag=sc:Mlym 6 {0D16 0D1C 0D25 0D3F 0D46-0D47}   Any character tagged as Malayalam
implicit Tag=sc:Taml 48 {0B83 0B85-0B8A 0B8E-0B90 0B92-0B95 0B99-0B9A 0B9C 0B9E-0B9F 0BA3-0BA4 0BA8-0BAA 0BAE-0BB9 0BBE-0BC2 0BC6-0BC8 0BCA-0BCD}   Any character tagged as Tamil


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.

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
Anchor Used as
Ref Comment
leading-combining-mark (start)[[\p{gc=Mn}]∪[\p{gc=Mc}]]       Default WLE rule matching labels with leading combining marks ⍟
follows-C ([:C:])← ⚓   C   Section 7, WLE 1, 2: H and M must be preceded by C
preceded-by-X ⚓ →([:X:])   C   Section 7, WLE 3 , X cannot be preceded by X
no-mix-sri-shri (\u0BB6\u0BCD\u0BB0\u0BC0.*\u0BB8\u0BCD\u0BB0\u0BC0)|(\u0BB8\u0BCD\u0BB0\u0BC0.*\u0BB6\u0BCD\u0BB0\u0BC0)       Section 7: WLE 4: Two representations of 'Shri' cannot be mixed in the same label


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.
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.
(... | ...) - 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.
. - any code point
. matches any code point.
*, +, ?, {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).
⍟ - 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 label matches no-mix-sri-shri invalid   do not mix two representations of 'Shri' in the same label
4 if at least one variant is in {blocked} blocked   any variant label containing blocked variants is blocked ⍟
5 if each variant is in {allocatable} allocatable   variant labels with all variants allocatable are allocatable ⍟
6 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.

5 Table of References

[1001] Omniglot, Tamil,
(Accessed on 21 Nov. 2017)
[1002] Unicode 11.0.0, South and Central Asia-I, Page 488-493, R5 and R5a,
(Accessed on 5 July. 2018)
[1003] Tamil Sign Visarga,
(Accessed on 27 Nov. 2017)