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This document specifies a set of Label Generation Rules (LGR) for the Thaana script using a script-specific repertoire for the second level domain or domains identified above. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Thaana Script” [Ref-LGR-und-Thaa], for details, see Change History below.
Standalone LGR: This LGR is designed to be used in a zone that does not cater to IDNs other than those valid under this LGR. This LGR lacks features that would allow its use in the context of another LGR in the same zone, and it may contain other features incompatible with such use.
For details and additional background on the Thaana script, see "Thaana Script Reference Label Generation Rules for Second-Level Domain Names" [Proposal-Thaana].
The repertoire includes the 49 letters and diacritics of the Thaana script in everyday use as defined in Section 5.1 “Included Code Points” in [Proposal-Thaana].
U+07B1 THAANA LETTER NAA (baru nūnu) is a dialect specific consonant. Given the resurgence of the use of the consonant in online writing and social media, a decision was made to include it in the repertoire at this time, despite it not being officially recognized as part of the base consonants.
For the second level, the repertoire has been augmented with the ASCII digits, U+0030 to U+0039, plus U+002D HYPHEN-MINUS, for a total of 61 repertoire elements.
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.
This LGR defines a number of in-script variants as described in Section 6.1 “In-script Variants”of [Proposal-Thaana]. No cross-script variants have been identified based on any discernable similarity with another script or otherwise required for the security of the Thaana LGR. However, if used in the context of an LGR for any other zone, variants may be required for the digits.
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, while any other equivalent labels should be blocked. There is no preference among these labels.
This LGR does not define allocatable variants.
The specification of variants in this LGR follows the guidelines in [RFC 8228].
Thaana has 25 consonants and 11 vowels. The first nine letters of Thaana are derived from the Arabic/Persian numerals (see below). The vowels are written above/below the letters.
By default, the LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.
Script-specific rules in this LGR already prevent combining marks in leading position making the "leading-combining-mark" rule technically redundant. It is retained here for consistency.
This LGR includes the complete set default actions for LGRs as well as the action needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940] and [150]. An additional action is triggered by mixed digit labels.
The LGR defines the following script-specific rules concerning the placement of vowels and preventing some combinations from starting a word.
This Second Level Reference LGR for the Thaana Script was developed by the Thaana community and edited by Asmus Freytag and Michel Suignard, based on community feedback and public review.
Adopted from the Second Level Reference LGR for the Thaana Script [Ref-LGR-und-Thaa] without normative changes.
This document cites the following general references.
References [0] to [3] refer to the Unicode Standard versions in which the corresponding code points were initially encoded. References [401] and above correspond to sources given in [Proposal-Thaana] justifying the inclusion of the corresponding cod5 points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, references [150] and [160] indicate the source for common rules.