This file contains Label Generation Rules (LGR) for the Cyrillic script for the Root Zone. For more details on this LGR and additional background on the script, see “Proposal for a Cyrillic Script Root Zone LGR” [Proposal-Cyrillic]. This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-5]. The format of this file follows [RFC 7940].
According to Section 5, “Repertoire” in [Proposal-Cyrillic], the Cyrillic script LGR contains 86 single code points. One additional sequence, U+0455 U+0455 has been added in integration to facilitate cross-script variant mappings. (This addition does not change the possible labels under this LGR.)
The repertoire only includes code points used by languages that are actively written in the Cyrillic script. All languages with [EGIDS] level 1 through 4 were included. Level 5 languages were analyzed and included on a case by case basis. The repertoire is based on [MSR-5], which is a subset of [Unicode 11.0].
Code points outside the Cyrillic 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.
As part of the Root Zone, this LGR includes neither decimal digits nor the HYPHEN-MINUS.
Each code point is tagged with the script or scripts with which the code point is used. For each repertoire element, one or more references document sufficient justification for inclusion in the repertoire; see “References” below. For code points that are part of the repertoire, comments identify the languages using it along with their [EGIDS] level.
According to Section 6, “Variants” in [Proposal-Cyrillic], there are no variants defined within the Cyrillic script. However, integration with the Latin and Greek LGR does introduce some in-script variants due to cross-script variant transitivity.
In particular, the Cyrillic LGR inherits the following in-script variants as result of integration:
This LGR inherits additional blocked cross-script variants by integration; they may not be listed here unless they result in in-script variants. However, for consistency, the variant mappings among the closely related scripts Armenian, Cyrillic, Greek and Latin are listed in full. See the merged, Common LGR [RZ-LGR-5] for details of all applicable cross-script variants, including any not listed here; always use the Common LGR for determining cross-script collisions of labels.
Where homoglyphs or near homoglyphs with Cyrillic code points exist in the Latin, Greek and Armenian scripts, out-of-repertoire variants are defined with a comment “Cross-script homoglyph”. As result of integration, including the effecs of cross-script transitivity, the number of cross-script variants listed for these scripts is larger than defined in Section 6, “Variants” in [Proposal-Cyrillic]. These are generally not marked.
Some cross-script variants originally defined in the proposal target code points that are not in the final repertoire of the Latin LGR. These mappings have been suppressed here.
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.
This LGR does not define allocatable variants.
The specification of variants in the Root Zone LGR follows the guidelines in [RFC 8228].
This LGR declares a cross-script variant between U+0073 and U+0455. Therefore the sequence U+0073 U+0073 is automatically a variant to any sequence U+0455 U+0455 occurring in a Cyrillic label. Now the Latin LGR [RZ-LGR-Latin] declares an in-script variant between U+0073 U+0073 and U+00DF. The Greek LGR [RZ-LGR-Greek] declares a variant between U+00DF and U+03B2. Transitivity on the code point level requires these additional code points to be listed as variants to a sequence U+0455 U+0455 that would normally not need to be defined in the Cyrillic LGR because it is redundant: the LGR supports the repetition of the singleton code point U+0455 without restriction. As result of integration, the redundant sequence U+0455 U+0455 is added here, together with its variants in the Greek and Latin script. Being redundant other than in the definition of variants, it does not change the labels available under this LGR.
The LGR does not define character classes.
The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-5]. They are marked with ⍟.
This LGR does not define rules specific to Cyrillic.
The Root Zone LGR for the Cyrillic script was developed by the Cyrillic Generation Panel. For methodology and contributors, see Sections 4 and 8 of [Proposal-Cyrillic], as well as [RZ-LGR-5-Overview]. After initial review by the Integration Panel, this LGR was deferred until it could be considered in the context of all related scripts. The LGR has been updated to reflect inherited variants resulting from integration.
The following general references are cited in this document:
For references consulted particularly in designing the repertoire for the Cyrillic 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 [100] to [122] correspond to sources given in [Proposal-Cyrillic] for justifying the inclusion of the corresponding code points. Entries in the table may have multiple source reference values.
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