Label Generation Rules for Russian

Overview

This document specifies a reference set of Label Generation Rules for Russian using a limited repertoire as appropriate for a second level domain.

Repertoire

All references converge on 33 Cyrillic code points (23 +10 as defined by RFC 5992 [130]).

There is an IDN table published in the IANA Repository of IDN Practices for Russian by .ru (Russia cctld) [700]. There are other new Cyrillic TLDs created in Russia, but they all use the same repertoire as .ru.

In Russian, the acute accent may be used as a stress mark on the vowel of a syllable or to disambiguate between minimal pairs. However, it is restricted to dictionaries and educational materials. See Stress and Disambiguation in [ACUTE].

Four code points: U+0456 (і) CYRILLIC SMALL LETTER BYELORUSSIAN-UKRAINIAN I, U+0463 (ѣ) CYRILLIC SMALL LETTER YAT, U+0473 (ѳ) CYRILLIC SMALL LETTER FITA, and U+0475 (ѵ) CYRILLIC SMALL LETTER IZHITSA were abolished from use in 1918; therefore they are not in modern use.

Excluded code points

Letters documented in some references but not included:

• U+0456 (і) CYRILLIC SMALL LETTER BYELORUSSIAN-UKRAINIAN I

• U+0463 (ѣ) CYRILLIC SMALL LETTER YAT

• U+0473 (ѳ) CYRILLIC SMALL LETTER FITA

• U+0475 (ѵ) CYRILLIC SMALL LETTER IZHITSA

• U+0430 U+0301 (а́) CYRILLIC SMALL LETTER A WITH ACUTE ACCENT

• U+0435 U+0301 (е́) CYRILLIC SMALL LETTER IE WITH ACUTE ACCENT

• U+0438 U+0301 (и́) CYRILLIC SMALL LETTER I WITH ACUTE ACCENT

• U+043E U+0301 (о́) CYRILLIC SMALL LETTER O WITH ACUTE ACCENT

• U+0443 U+0301 (у́) CYRILLIC SMALL LETTER U WITH ACUTE ACCENT

• U+044B U+0301 (ы́) CYRILLIC SMALL LETTER YERU WITH ACUTE ACCENT

• U+044D U+0301 (э́) CYRILLIC SMALL LETTER E WITH ACUTE ACCENT

• U+044E U+0301 (ю́) CYRILLIC SMALL LETTER YU WITH ACUTE ACCENT

• U+044F U+0301 (я́) CYRILLIC SMALL LETTER YA WITH ACUTE ACCENT

Extended code points

None.

Variants

None.

Note: a study of the variant relationship concerning U+0435 (е) CYRILLIC SMALL LETTER IE and U+0451 (ё) CYRILLIC SMALL LETTER IO was undertaken in the context of Russian by a Cyrillic case study team in [CYRILLIC-VIP]. The expert team concluded: "...even if relationships between these two characters might look as variant-like, they are not symmetrical and these two letters are not considered equivalents in Russian language." (page 5, section 3.1)

Character Classes

This LGR defines no named character classes.

Rules

Common rules only:

• Hyphen Restrictions — restrictions on the allowable placement of hyphens (no leading/ending hyphen and no hyphen in positions 3 and 4). These restrictions are described in section 4.2.3.1 of RFC5891 [120]. They are implemented here as context rule on U+002D (-) (-) HYPHEN-MINUS.

• Leading Combining Marks — restrictions on the allowable placement of combining marks (no leading combining mark). This rule is described in section 4.2.3.2 of RFC5891 [120].

Actions

Actions included are the default actions for LGRs as well as those needed to invalidate labels with misplaced combining marks.

Variant-related actions included to facilitate integration as appropriate.

Methodology and Contributors

This reference LGR for Russian for the 2nd Level has been developed by Michel Suignard and Asmus Freytag, verified in expert reviews by Michael Everson, Nicholas Ostler, and Wil Tan, and based on multiple open public consultations.

References

General references for the language:

• Barry, Randall K. 1997. ALA-LC romanization tables: transliteration schemes for non-Roman scripts. Washington: Library of Congress Cataloging Distribution Service. ISBN 0-8444-0940-5

• Timberlake, Alan. 1993."Russian", in Bernard Comrie & Greville G. Corbett, eds. The Slavonic languages. London; New York: Routledge. ISBN 0-415-04755-2

• Смирницкий, А И. 1989. Русско-английскиѝ словарь = Russian-English dictionary. Москва: Русский язык. ISBN 5-200-00-718-6

Other references cited in this document:

[ACUTE]

Wikipedia, "Acute accent"
https://en.wikipedia.org/wiki/Acute_accent

[CYRILLIC-VIP]

Sozonov, A. et al., “IDN Variant TLDs – Cyrillic Script Issues”. (Marina del Rey, California: ICANN, October 2011).
http://archive.icann.org/en/topics/new-gtlds/cyrillic-vip-issues-report-06oct11-en.pdf.

In the listing of the repertoire by code point, references starting from [0] refer to the version of the Unicode Standard in which the corresponding code point was initially encoded. Other references, (starting from [100]) document usage of code points. For more details, see the Table of References below.

Character Classes

The following table lists all named 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
implicit	Tag=sc:Cyrl	33 Elements:	{0430-044F 0451}
implicit	Tag=sc:Zyyy	11 Elements:	{002D 0030-0039}

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. (Any use of context rules for variants is not indicated).

Name	Used as Trigger	Used as Context	Anchor	Regular Expression	Ref	Comment
leading-combining-mark	✔			(^[∅=[[∅=\p{gc=Mn}][∅=\p{gc=Mc}]]])	[120]	RFC5891 restrictions on placement of combining marks
hyphen-minus-disallowed		✔	✔	((((?<=^)⚓)|(⚓(?=$))|((?<=^..\u002D)⚓)))	[120]	RFC5891 restrictions on placement of U+002D
extended-cp				(^$)		code points from the extended range

Note: The following rules are defined but not used in this LGR: extended-cp.

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		by default, labels with leading combining marks are invalid
2	if any label (catch-all)		→	valid		catch all (default action)