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Label Generation Rules for the Greek Script

Overview

This document specifies a set of Label Generation Rules (LGR) for the Greek script for the second level domain or domains identified above. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Grek]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Greek Script” [Ref-LGR-und-Grek], for details, see Change History below.

For details and additional background on the Greek script, see “Proposal for a Greek Script Root Zone LGR” [Proposal-Greek].

Repertoire

The repertoire contains the 36 code points used in writing the Greek language, according to [Proposal-Greek]. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Greek]. (The proposal cited has been adopted for the Greek script portion of the Root Zone LGR.)

No Greek code points from [MSR-5] have been excluded.

The repertoire includes code points used by the modern-day Greek language, which is the official language of Greece and Cyprus. The repertoire also covers the Pomak language, which is the only “non-Greek” language that uses Greek characters nowadays. For more details, see Section 5 “Repertoire” in [Proposal-Greek]).

For the second level, the repertoire has been augmented with the ASCII digits, U+0030 0 to U+0039 9, plus U+002D - HYPHEN-MINUS, for a total of 47 repertoire elements.

Any code points outside the Greek Script repertoire that are targets for out-of-repertoire variants would be included here only if the variant is listed in this file. In this case they are identified as a reflexive (identity) variant of type “out-of-repertoire-var”. Whether or not they are listed, they do not form part of the repertoire.

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 references documenting sufficient justification for inclusion in the repertoire, see “References” below.

Variants

The variants defined in this LGR are limited to those required for use in zones not shared with any other script. As such, this LGR does not define cross-script variants. However, using this LGR concurrently with any LGR for Armenian, Cyrillic, and Latin in the same zone will create potential cross-script issues. For details, see Section 6, “Variants” in [Proposal-Greek]. Mitigation of these cross-script variants can be addressed by using the Common LGR. For details, see Section 3, “Use of Multiple Reference LGRs in the Same Zone” in [Level-2-Overview]. In addition to variants defined by this LGR, the full variant information related to this script and required for concurrent use with the Armenian, Cyrillic, and Latin LGR(s) can be found in the following LGR: [Ref-LGR-Latin-Full-Variant-Script]

In-script variants defined in this LGR largely follow the methodology defined in Section 6, “Variants”, in [Proposal-Greek].

The LGR defines certain allocatable fallback variants as described in Section 4.5.5 “Allocatable Fallback Variants” in [Level-2-Overview]. A fallback variant is a variant label that uses substitute code points for code points or sequences not available (or not allowed) in some contexts, that would otherwise be required for a linguistically accurate rendering of some label.

When “fallback” variants are defined, two labels may be allocated: a single label with the spelling preferred by the applicant, plus a single fallback variant for that label. The fallback exclusively uses the fallback characters for any characters for which fallbacks are defined, while the “preferred” label may use any otherwise valid mix of code points. If the fallback variant is the one applied for, no other variant label is allocatable.

Allocatable fallback variants exists for the following cases:

• Greek vowels with and without accent — all Greek vowels with Tonos and/or Dialytika have an allocatable fallback variant which is the same vowel without tonos and/or dialytika. While correct spelling would require the accent, the fallback is readily accepted.
• U+03C2 ς GREEK SMALL LETTER FINAL SIGMA and U+03C3 σ GREEK SMALL LETTER SIGMA — IDNA2003 Compatibility: in IDNA2003, U+03C2 ς GREEK SMALL LETTER FINAL SIGMA is mapped into U+03C3 σ GREEK SMALL LETTER SIGMA. Therefore, U+03C3 σ is defined as allocatable fallback for U+03C2 ς.

In-script Variant Mapping Types

In each of the fallback variant pairs defined above, the mapping type from the first element to the second is of type “fallback”, while the variant type for the other direction is “blocked”. In addition, the first element of each pair uses the reflexive mapping “r-original”. (By convention, the prefix “r-” marks a type used in a reflexive variant mapping, that is, it represents an instance of the original code point at that location in a variant label, see Section 5.3.4 in [RFC 7940].)

Variant Disposition: Except for limited exceptions for the fallback variants defined above, variants defined here result in a variant label disposition of “blocked”.

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

Character Classes

This LGR does not define named character classes.

Whole Label Evaluation (WLE) and Context Rules

Default Whole Label Evaluation Rules and Actions

By default, the LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.

• 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 RFC 5891 [150]. 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 RFC 5891 [150].

Greek specific Rules

This LGR does not define rules specific to the Greek script.

Actions

Default Actions

This LGR includes the 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].

Because this LGR defines allocatable fallback variants the following default actions are applicable.

• blocked — a variant label containing a blocked variant will receive a disposition of “blocked”.
• r-original — a label containing one or more of this reflexive variant type and no others represents an original label and receives a disposition of “valid”.
• fallback — a label containing one or more of these variant types and no others represents a label that contains only fallback variants and receives a disposition of “allocatable”.
• fallback plus other — any label remaining containing both this variant type and any others receives a disposition of “blocked”.

These actions resolve as “allocatable” any label where all variants are of type “fallback”, and as “valid” any label where all variants are of type “r-original”. Labels with a mix of variant types are resolved as “blocked”.

To account for original code points in a permuted variant, reflexive variant mappings with an “r-” prefix are used. (See [RFC 7940]). In particular, the mapping type “r-original” is given to any code point that has a fallback mapping, but that appears in its non-fallback form in the original label, and thus “maps to itself”.

Default actions that are triggered by the LGR-specific variant types described above limit the “allocatable” variant labels to those containing only unaccented vowel or nonfinal sigma variants or both, while disallowing mixed use of accented and unaccented vowels or final and nominal forms of sigma, except as in the original applied-for label.

Note that the mapping types for variants are not symmetric: they depend on which code point is considered the source or the target in a given mapping. As specified in [RFC 7940], when mapping types are evaluated code points in a label that are unchanged use the type of their “reflexive” mapping. Per [RFC 7940] the actions are always applied one after the other, and the evaluation stops at the first action that assigns a disposition to a given label.

Methodology and Contributors

The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Greek Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Greek script and information contained or referenced therein; see [RZ-LGR-Grek]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. The original proposal for a Root Zone LGR for the Greek script, that this LGR is based on, was developed by the Greek Generation Panel. For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Greek], as well as [RZ-LGR-Overview].

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Greek Script [Ref-LGR-und-Grek] without normative changes.

References

The following general references are cited in this document:

[EGIDS]

Lewis and Simons, “EGIDS: Expanded Graded Intergenerational Disruption Scale,” documented in [SIL-Ethnologue] and summarized here:
https://en.wikipedia.org/wiki/Expanded_Graded_Intergenerational_Disruption_Scale_(EGIDS)

[Guidelines]

ICANN, “Guidelines for Developing Reference LGRs for the Second Level”, (Los Angeles, California: ICANN, 27 May 2020),
https://www.icann.org/en/system/files/files/lgr-guidelines-second-level-27may20-en.pdf

[Level-2-Overview]

Internet Corporation for Assigned Names and Numbers, (ICANN),“Reference Label Generation Rules (LGR) for the Second Level: Overview and Summary” (PDF), (Los Angeles, California: ICANN, 24 January 2024),
https://www.icann.org/en/system/files/files/level2-lgr-overview-summary-24jan24-en.pdf

[MSR-5]

Integration Panel, “Maximal Starting Repertoire — MSR-5 Overview and Rationale”, 24 June 2021,
https://www.icann.org/en/system/files/files/msr-5-overview-24jun21-en.pdf

[Proposal-Greek]

Greek Generation Panel, “Proposal for a Greek Script Root Zone Label Generation Rule-Set (LGR)”, 1 February 2022,
https://www.icann.org/en/system/files/files/proposal-greek-lgr-01feb22-en.pdf

[Ref-LGR-und-Grek]

ICANN, Second Level Reference Label Generation Rules for the Greek Script (und-Grek), 24 January 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-greek-script-24jan24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-greek-script-24jan24-en.html

[Ref-LGR-Latin-Full-Variant-Script]

ICANN, Second Level Reference Label Generation Rules for the Latin Script (und-Latn), 24 January 2024 (XML)
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-latin-full-variant-script-24jan24-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/packages/lgr/lgr-second-level-latin-full-variant-script-24jan24-en.html

[RZ-LGR-Grek]

ICANN, Root Zone Label Generation Rules for the Greek Script (und-Grek), 26 May 2022 (XML)
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-greek-script-26may22-en.xml

[RFC 7940]

Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
https://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

[RZ-LGR-Overview]

Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022 (PDF),
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-overview-26may22-en.pdf

[RZ-LGR-5]

Integration Panel, “Root Zone Label Generation Rules (RZ-LGR-5)”, 26 May 2022 (XML),
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-common-26may22-en.xml
non-normative HTML presentation:
https://www.icann.org/sites/default/files/lgr/rz-lgr-5-common-26may22-en.html

[SIL-Ethnologue]

David M. Eberhard, Gary F. Simons & Charles D. Fennig (eds.). 2021. Ethnologue: Languages of the World, Twenty fourth edition. Dallas, Texas: SIL International. Online version available as
https://www.ethnologue.com

[Unicode 11.0.0]

The Unicode Consortium. The Unicode Standard, Version 11.0.0, (Mountain View, CA: The Unicode Consortium, 2018. ISBN 978-1-936213-19-1)
https://www.unicode.org/versions/Unicode11.0.0/

For references consulted particularly in designing the repertoire for the Greek Script for the second level 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. Reference [101] corresponds to the source given in [Proposal-Greek] for justifying the inclusion of the corresponding code points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, reference [150] indicates the source for common rules.

Character Classes

Implicit (except script)	1
Implict defined by script tag	2

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
implicit	Tag=Common-digit	10	{0030-0039}		Any character tagged as Common-digit
implicit	Tag=sc:Grek	36	{0390 03AC-03CE}		Any character tagged as Greek
implicit	Tag=sc:Zyyy	11	{002D 0030-0039}		Any character tagged as Common

Legend

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 "...".

Tag=ttt

A named or implicit class defined by all code points that share the given tag value (ttt).

Implicit

An anonymous class implicitly defined based on tag value and for which there is no named equivalent.

Whole label evaluation and context rules

Number of rules	2
Used to trigger actions	1
Used as context rule (C)	1
Anchored context rules	1

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 Trigger	Anchor	Used as Context	Ref	Comment
leading-combining-mark	(start)[∅=[[∅=\p{gc=Mn}] ∪ [∅=\p{gc=Mc}]]]	✔			[150]	RFC 5891 restrictions on placement of combining marks ⍟
hyphen-minus-disallowed	(((start))← ⚓︎)|(⚓︎ →((end)))|(((start)..\u002D)← ⚓︎)		✔	C	[150]	RFC 5891 restrictions on placement of U+002D - ⍟

Legend

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.

Anchor

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.

( ) - group

An anonymous nested rule is used to group match operators.

(... | ...) - 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.

[\p{ }] - property

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).

∅= - empty set

Indicates that the following set is empty because of the result of set operations, or because none of its elements is part of the repertoire defined here. A rule with a non-optional empty set never matches.

⍟ - default rule

Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

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 at least one variant is in	{blocked}	→	blocked		any variant label containing blocked variants is blocked ⍟
4	if each variant is in	{allocatable}	→	allocatable		variant labels with all variants allocatable are allocatable ⍟
5	if each variant is in	{fallback}	→	allocatable		any label with all variants of type fallback is allocatable ⍟
6	if at least one variant is in	{fallback}	→	blocked		any variant label with a mix of variant forms is blocked ⍟
7	if each variant is in	{r-original}	→	valid		any remaining label containing only original code points is valid ⍟
8	if any label (catch-all)		→	valid		catch all (default action) ⍟

Legend

{...} - 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.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.