Characters recommended in both UTS#39 and MSR but excluded from the Root Zone or Reference LGR

This document has been submitted as a UTC document. For convenience in documenting the character list it is presented using an LGR template format. A few minor details of the boilerplate in that template may not be applicable in this context and should be disregarded.

The collection comprises 274 characters included in the Maximal Starting Repertoire [MSR] for the DNS Root Zone that are also recommended in UTS#39 but are not part of the Second Level Reference LGR [RefLGR], as well as the uppercase equivalents for 88 of them (Latin), plus 70 decimal digits excluded from the Reference LGR, for a total of 432 characters.

Recommendation

• Proposed:Uncommon_Use (386)—The majority of these 432 characters are proposed for reclassification to Uncommon_Use, based on the fact that the expert teams charged with reviewing them for the ICANN Root Zone LGR and Reference LGR for the Second Level could not come up with evidence that they are used in common everyday writing, even for minority languages in reasonably widespread use. Consequently, they declined to include them in the respective LGRs.
• Proposed:Technical (1)— A few character were found to be in specialized use and are proposed as Technical.
• Proposed:Obsolete (5)—A few characters were found to no longer in use and are proposed as Obsolete.
   
• Recommended (40)—In review, some of the characters are found to have documented use that is compatible with retaining their Identifier_Type of Recommended. These characters are tagged with Identifier_Type Recommended and no change is proposed.
• Review_Needed (0)—Any characters tagged as Review_Needed would need additional review before a recommendation can be proposed for them. This set should be empty by the time the proposal is finalized.

The table in Section 2, “Repertoire” lists the characters with their proposed or existing Identifier_Type values in the “Tags” column, together with references to the source of their classification, as well as any other information. Because this document only includes characters not added to and therefore not listed in [RefLGR], this source is not documented on the character level. The [MSR] is limited to characters that are PVALID and thus isn't cited for digits or uppercase characters.

Additional Recommendations

The document contains some other recommendations in addition to reassigning Identifier_Type. They are:

• Proposed language on combining marks for UTS#39. See “Combining Marks”
• Proposed language for UAX#31 on challenges in using Tibetan Script until it is properly vetted for identifiers. See “Tibetan Script”
• Create an Invariance test to ensure that uppercase characters have the same Identifier_Type as their lowercase equivalents, so that identifier validity does not depend on case mapping.

Background

There are over a thousand non-Han characters with Identifier_Type Recommended that are proposed for consideration of reclassification because they appear to fail reasonable criteria for being needed in identifiers. They come in two sets. For one set, an independent analysis [MSR] has found indications that they should have been considered Uncommon_Use, Obsolete or Technical based on information available at the time of encoding, including their uppercase equivalents and any native digits that can be considered obsolete. That set is discussed in another document. The second set contains characters that were tentatively included in the [MSR] but upon further review by local expert teams from the [RZ-LGR] project were found to not be needed for any language or minority language in reasonably widespread use. That second set is discussed here.

The initial analysis was carried out for the purposes of defining the allowed repertoire for IDN Top Level Domain names for the DNS Root Zone. There are some restrictions that are specific to the Root Zone, such as a prohibition on digits, so a follow-on effort determined how to relax these restrictions in a manner appropriate for the needs of Second-Level Domains. This resulted in the Second-Level Reference Label Generation Rules [RefLGR]. The characters listed in this document are those that were not added to the [RefLGR], for lack of evidence of their use in everyday common writing for any language or minority language in vigorous and reasonably widespread use.

The set of characters discussed in this document starts with all characters of Identifier_Type Recommended, subtracting any character disallowed in [MSR] and then subtracting any character included in [RefLGR]. Added to the set are any uppercase equivalents as well as any native digits in that were not added to the [RefLGR] due to not being in common use.

The implication here is that any character not included in the Reference LGR for lack of documented or identifiable usage should be considered Uncommon_Use for Unicode's default identifiers—until such time as independent evidence to the contrary is produced, or a different Identifier_Type is proposed as a better fit. Until then, in lack of a demonstrated use case, it seems not helpful to continue to suggest that these characters should be supported as recommended. This also applies to any sets of native digits for which local experts considered them uncommon_use for the purpose of identifiers.

Arriving at a precise cutoff for Uncommon_Use is difficult because there is no single source or perfect information on the use of writing systems, and the details of such use are changing over time. In the research cited, that determination started with the [EGIDS] classification as a proxy for the likely level of modern use of the writing system, but made further adjustments in expert review. Accordingly, this document suggests that the UTC should consider the published results of the cited research as one of the better sources of information available and only deviate from it on the basis of even better information.

All decisions for the classification of characters in [MSR], or inclusion in [RZ-LGR] and [RefLGR] are documented and sourced on the character level; the same is not true for Unicode's classification, so it is not easily possible to verify any of the decisions that underlie the classification published in UTS39. By first making the alignment proposed here, and then carefully documenting deviations, a positive side effect might be that the classification overall becomes more transparent and reviewable.

For further background on specific disposition for characters in the DNS Root Zone [RZ-LGR] and Second-Level Reference LGR [RefLGR] see the cited references and links therein.

Additional Notes

• U+0931 ऱ DEVANAGARI LETTER RRA is part of the Root Zone and Reference LGR via sequence (does not occur standalone)
• U+09BC  ়  BENGALI SIGN NUKTA is part of the Root Zone and Reference LGR via sequence (does not occur standalone)
• U+0DA6 ඦ SINHALA LETTER SANYAKA JAYANNA is part of the Root Zone and Reference LGR via sequence (does not occur standalone)
• U+0E45 ๅ THAI CHARACTER LAKKHANGYAO is part of the Root Zone and Reference LGR via sequence (does not occur standalone)
• U+1063  ၣ  MYANMAR TONE MARK SGAW KAREN HATHI is part of the Root Zone and Reference LGR via sequence (does not occur standalone)

Although they are not listed as standalone, they are part of the set of code points used in the repertoire of Root Zone and Reference LGR and therefore no change in their existing Identifier_Type is proposed, and they are not listed below.

Discussion and Review

Domain names are an important and deliberately conservative set of identifiers. That said, there may be other classes of identifiers that don't require the same level of restrictions, so this proposal should not be understood to suggest that default Identifiers must be restricted to only those characters that are being recommended for IDNs. Rather, the purpose is to bring the facts discovered during the development of the IDN repertoire for the DNS Root Zone and the [RefLGR] to the attention of the Unicode Technical Committee, so that characters that were classified Recommended can be given additional scrutiny before confirming their status.

The set of Proposed:Uncommon_Use has been mechanically compared to existing sets of exemplars using the UnicodeSets utility. Only a very small number of discrepancies were found, but in all cases, the respective source documents (proposals) documented deliberate decisions to exclude them, confirming the proposal to mark these as Uncommon_Use. The only exceptions to this can be found in the Arabic script.

Arabic Script

As review progresses, a number of characters have been identified with usage as documented in comments and references. For some, the nature of the use should be adjusted:

• U+0671 ٱ ARABIC LETTER ALEF WASLA - this letter is considered to be “an important Quranic character”. Changed to Proposed:Technical.
• U+06C7 ۇ ARABIC LETTER U - this letter was considered by “Proposal for Arabic Script Root Zone LGR”, [Proposal-Arabic] only for Kirghiz and Azerbaijani, for which the proposal concludes “No evidence found for active use” but it turns out it is used for Kazakh and is also part of the name of the Uyghur language “ئۇيغۇر”, and in places where an Arabic orthography is preferred. See [AZ], [KK], [KY] and [UG]. Retained as Recommended.
• U+06CA ۊ ARABIC LETTER WAW WITH TWO DOTS ABOVE - this letter is used for Southern Kurdish, which is listed as “threatened” by [SDH-G]. However, the characters is listed in all the sources for the other Kurdish characters [KU-S], [KU-Wk] and [ISO-11822] and should be treated consistently. Retain as Recommended/
• U+0682 ڂ ARABIC LETTER HAH WITH TWO DOTS VERTICAL ABOVE appears to be used in Khowar, a language of 300K–600K speakers. However, [KHW-G] notes the language as “at risk”(20% certain). Note, the writing systems for Khowar are relatively recent, but the [EGIDS] level is reported as 3. Retain as Recommended.
• U+0690 ڐ ARABIC LETTER DAL WITH FOUR DOTS ABOVE has been changed to Proposed:Obsolete. As far as we know, it only has historic use.
• U+0692 ڒ ARABIC LETTER REH WITH SMALL V, U+0694 ڔ ARABIC LETTER REH WITH DOT BELOW, and U+06B6 ڶ ARABIC LETTER LAM WITH DOT ABOVE are claimed to be used in Kurdish by both SIL [KU-S] and Wiktionary [KU-Wk] . [ISO-11822] also lists them being used in Kurdish. Based on that, their use with the writing system might be considered established. The classification would depend on the usage level for the writing system. Retain as Recommended
• U+06EE ۮ RABIC LETTER DAL WITH INVERTED V, U+06EF ۯ ARABIC LETTER REH WITH INVERTED V, and U+06FF ۿ ARABIC LETTER HEH WITH INVERTED V are used in the standardized orthography for Parkari Koli, a language of 250K–319K speakers, see [KVX-W] and [KVX-O]. The EGIDS level is given as 5 (Developing) by [KVX-G]. Retain as Recommended
• U+06A5 ڥ is in common use in Algeria and Tunisia for brands. Roozbeh Pournader reports personally seeing this in advertisements in Tunisia, circa 2002, specifically a brand named Viva (ڥيڥا). It is also used in writing words like "video" according to an entry in the [Tu-Wk] Google shows several results too [Tu-Gg] Retain as Recommended.
• U+06B7 ڷ is used in Brahui (2.2M–2.8M speakers). It's also used in some smaller languages. According to [BRH-O] “Brahui has no official status, and is not used in education or government administration”. [BRH-W] notes that there is a competing Latin-based writing system. [BRH-G] documents the status as “threatened”, but [EGIDS] is level 5. Retain as Recommended.
• U+06D3 ۓ is used in Urdu as documented by [UR-RI].It appears that the letter is used in common words such as “tea” (چاۓ). See also [ۓ: ">UR-Gg] . Retain as Recommended.

In [Proposal-Arabic] the repertoires needed for the Arabic Alphabets used for Southern Azerbaijani in Iran [AZ], and for Uyghur [UG], Kazakh [KK], and Kyrgyz [KY] in China, the latter with their own published standards, do not appear to have been included in that document. A more detailed review based on documented repertoires for these writing systems suggests a few characters (U+06C5 ۅ, U+06C7 ۇ..U+6CA) that should be attested after all.

See also “Combining Marks”.

Bengali (Bangla) Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+098C ঌ BENGALI LETTER VOCALIC L — listed in the exemplars for the Bengali (Bangla) language.

As discussed in Section 4.2.1.3, “No Rare and Obsolete Characters” of [Proposal-Bengali]:

There are characters which have been added to Unicode to accommodate rare forms such as Sanskritic ... VOCALIC L “ঌ” (U+098C) ... All such characters are excluded...

Cyrillic Script

The following character is excluded from the DNS Root Zone and Reference LGR for the Second level, based on its particular use, which is not relevant to identifiers.

• U+045D ѝ CYRILLIC SMALL LETTER I WITH GRAVE — The character 'ѝ' presents the stressed version of 'и' and is used in Bulgarian and Macedonian with the purpose of differentiating the short female version of the object in a sentence from the conjunction 'и'. See [Proposal-Cyrillic].

Devanagari

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+090C ऌ DEVANAGARI LETTER VOCALIC L — listed in the exemplars for several languages, including hindi and sanskrit (doi,hi,kok,mr,ne,sa)

As discussed in Section 5.3, “Code points not included” of [Proposal-Devanagari]:

Reason for Exclusion: Not in modern usage...

Ethiopic Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+1347 ፇ ETHIOPIC SYLLABLE TZOA — listed in the exemplars for the Tigrigna language.

As discussed in Section 5.3, “Code Points Excluded from the Repertoire” of [Proposal-Gurmukhi]:

...the following code points have been excluded from the code point repertoire of the Ethiopic script LGR as there has not been any occurrence of the code point in the corpus data analysed for online contents published in Amharic and Tigrigna languages...

Gurmukhi Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+0A72 ੲ GURMUKHI IRI — listed in the exemplars for the Punjabi language.
• U+0A73 ੳ GURMUKHI URA — listed in the exemplars for the Punjabi language.

As discussed in Section 4.1.6, “No Vowel Carriers” of [Proposal-Gurmukhi]:

Gurmukhi script has three vowel carriers ( URA, ੳ (U+0A73), AIRA ਅ (U+0A05) and IRI, ੲ (U+0A72)). They are used as vowel carriers and thus always need to be followed by some matra when used in text. ... where these vowel carriers occur with a matra they will be identical with one of the independent vowels (ਉ (U+ 0A09), ਊ (U+ 0A0A), ਇ (U+ 0A07), ਈ (U+ 0A08), ਏ (U+ 0A0F), ਓ (U+ 0A13); this is also not allowed in Unicode. Thus ੳ (U+0A73) + ◌ੁ (U+0A41), which looks the same as ਉ (U+ 0A09), will create confusion and hence will not be allowed in the LGR. As the vowel carriers ੳ (U+0A73) and IRI, ੲ (U+0A72) cannot occur independently, ... these letters are not included in the repertoire.

Hebrew scripts

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+05F2 ײ – HEBREW LIGATURE YIDDISH DOUBLE YOD — listed in the exemplars for the Yiddish language.

As discussed in Section 5.1.5, “Special Hebrew Code Points” of [Proposal-Hebrew]:

..DOUBLE YOD. Intended for use in Yiddish texts, this code point provides a special combined ligature for two consecutive HEBREW LETTER YOD.

All [...] of these code points are excluded ... [These ligatures] might be confused with their respective combinations of two single letters. In addition, they can be adequately replaced by their respective combination of two consecutive single letters – DOUBLE YOD by two consecutive YOD, etc. Another advantage of these equivalent replacements is that they can be typed using a standard Hebrew-mapped keyboard.

Kannada Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+0C8C ಌ KANNADA LETTER VOCALIC L — listed in the exemplars for the Kannada language.
• U+0CB1 ಱ KANNADA LETTER RRA — listed in the exemplars for the Kannada language.

As discussed in Section 5.3, “Codepoints not included” of [Proposal-Kannada]:

Reason for Exclusion: U+0C8C ಌ Not in modern usage; U+0CB1 ಱ Obsolete character, not used in modern Kannada

Khmer Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+17A9 ឩ KHMER INDEPENDENT VOWEL QUU — listed in the exemplars for the Punjabi language.
• U+17B2 ឲ KHMER INDEPENDENT VOWEL QOO TYPE TWO — listed in the exemplars for the Punjabi language.

As discussed in Section 5.2, “Independent Vowels” of [Proposal-Khmer]:

...two independent vowels have been excluded from the repertoire. ... The vowel ឩ KHMER INDEPENDENT VOWEL QUU (U+17A9) has been excluded because it is not commonly used in the Khmer dictionary, and [the] few words using this letter now have alternate spellings without it. For example, ឩដ្ឋ (ūdth, camel) is now spelled as អូដ្ឋ ... Moreover, no new words use this code point.

... ឲ KHMER INDEPENDENT VOWEL QOO TYPE TWO (U+17B2) ... is a variant for ឱ Khmer INDEPENDENT VOWEL QOO TYPE ONE (U+17B1). The vowel ឲ KHMER INDEPENDENT VOWEL QOO TYPE TWO (U+17B2) is used to write only one word, the verb “give” but now Choun Nath Khmer Dictionary, which is an authoritative source on Khmer, writes the word as ឱយ (ooy, give) with ឱ KHMER INDEPENDENT VOWEL QOO TYPE ONE(U+17B1) instead.

Resolved in discussion to retain U+17B2 ឲ as Recommended as online search reveals that the cutover to the new spelling is not universal.

Latin Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as CLDR exemplars for various languages.

• U+014F ŏ LATIN SMALL LETTER O WITH BREVE — listed in the exemplars for the Silesian language. EGIDS level 6a. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+0157 ŗ LATIN SMALL LETTER R WITH CEDILLA — listed in the exemplars for the Prussian language. EDIDS level 9. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+01F9 ǹ LATIN SMALL LETTER N WITH GRAVE — listed in the exemplars for several languages (bas,blo,ewo,jgo,yo). The use of accents on nasal consonants is described in [YO-W], and n with grave can be found in a recent corpus [YO-L]. Therefore, U+01F9 ǹ should remain Recommended.
• U+021F ȟ LATIN SMALL LETTER H WITH CARON — listed in the exemplars for the Lakota language. EGIDS level 8a. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E0D ḍ LATIN SMALL LETTER D WITH DOT BELOW — listed in the exemplars for several languages (kab,kxv,shi-Latn,tzm). According to [KAB] there are a significant number of speakers, and the writing system is probably not as stable as the use as an oral language. The status and recognition seem to have seen some recent improvement so arguably this character should remain Recommended.
• U+1E11 ḑ LATIN SMALL LETTER D WITH CEDILLA — listed in the exemplars for the Prussian language, EGIDS level 9. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E25 ḥ LATIN SMALL LETTER H WITH DOT BELOW — listed in the exemplars for several languages (ast,kab,shi-Latn,tzm). According to [KAB] there are a significant number of speakers, and the writing system is probably not as stable as the use as an oral language. The status and recognition seem to have seen some recent improvement so arguably this character should remain Recommended.
• U+1E3F ḿ LATIN SMALL LETTER M WITH ACUTE — listed in the exemplars for several languages (blo,jgo,nnh,yo), the use of accents on nasal consonants is described in [YO-W], and m with acute can be found in a recent corpus [YO-L]. Therefore, U+1E3F ḿ should remain Recommended.
• U+1E5B ṛ LATIN SMALL LETTER R WITH DOT BELOW — listed in the exemplars for several languages (kab,kxv,shi-Latn,tzm). According to [KAB] there are a significant number of speakers, and the writing system is probably not as stable as the use as an oral language. The status and recognition seem to have seen some recent improvement so arguably this character should remain Recommended.
• U+1E7D ṽ LATIN SMALL LETTER V WITH TILDE — listed in the exemplars for the Mundang language. While nasalization of vowels is indicated with tilde [MUA], there's no independent corroboration that this is used with the letter v. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E81 ẁ LATIN SMALL LETTER W WITH GRAVE — listed in the exemplars for the Welsh language. the use of grave with letter w is described as optional in [CY-O]. It does not appear a single time in a large corpus [CY-L]. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E83 ẃ LATIN SMALL LETTER W WITH ACUTE — listed in the exemplars for the Welsh language. The use of acute with letter w is described as optional in [CY-O]. It is rare and only appears a few times in a large corpus [CY-L]. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E85 ẅ LATIN SMALL LETTER W WITH DIAERESIS — listed in the exemplars for several languages (cy,jgo,nnh). The use of diaeresis with letter w in Welsh is described as optional in [CY-O]. It appear extremely rarely in a large corpus [CY-L]. While its use with Ngieboon is described in [NNH], the EGIDS level is 5 with a small population of language users and unknown literacy. For Ngomba (related to Ngieboon) no detailed information was found. Therefore, the proposal to make it Uncommon_Use is unchanged.
• U+1E93 ẓ LATIN SMALL LETTER Z WITH DOT BELOW — listed in the exemplars for the Kabyle language. According to [KAB] there are a significant number of speakers, and the writing system is probably not as stable as the use as an oral language. The status and recognition seem to have seen some recent improvement so arguably this character should remain Recommended.

The following lists the [EGIDS] levels for the languages involved. Where the level warranted a double-check, the results were added above. Unless noted there's no change to the proposal.

• Welsh (cy/cym): 2
• Yoruba (yo/yor): 2
• Ewondo (ewo): 3
• Kabyle (kab): 3
• Anii (blo): 5
• Basaa (bas): 5
• Kuvi (kxv): 5
• Mundang (mua): 5
• Ngiemboon (nnh): 5
• Ngomba (jgo): 5
• Tachelhit (shi): 5
• Silesian (szl): 6a
• Asturian (ast): 6b
• Central Atlas Tamazight (tzm): 6b
• Lakota (lkt): 8a
• Prussian (prg): 9

Oriya Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+0B35 ଵ ORIYA LETTER VA — listed in the exemplars for the Oriya language

As discussed in Section 5.2.1, “Code Points Excluded” of [Proposal-Oriya]:

The character Va “ଵ”(0B35) is used in form of handwritten character by few linguistics or has recently been used in a few websites on the internet. But this code point is not very frequently used in mass educational institutions, printed in mass communication, like newspapers or magazines. Some textbooks in the schools and college explain the plosive "Ba" ବ(0B2C) and non-plosive "Va" ଵ(0B35) separately as varga (plosive) and non-varga (non-plosive) respectively.

The public comment version of the Oriya Script LGR, NBGP had included the character Va “ଵ”(0B35) in the repertoire. However, the public comment feedback suggested that this use was not sufficiently common, and further analysis by NBGP concluded that "Va" ଵ(0B35) is not used in commonly printed books, magazines, etc. Therefore, it is excluded from the repertoire.

However, in coming years if this character is seen in frequent use, NBGP may reconsider including it in a later version of its LGR for the Oriya script.

Sinhala Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+0D9E ඞ SINHALA LETTER KANTAJA NAASIKYAYA — listed in the exemplars for the Sinhala language

As discussed in Section 5.4, “Code point not included” of [Proposal-Sinhala]:

Reason for Exclusion: Not in modern usage.

Telugu Script

The following characters are excluded from the DNS Root Zone and Reference LGR for the Second level, though listed as exemplars.

• U+0C0C ఌ TELUGU LETTER VOCALIC L — listed in the exemplars for the Telugu language
• U+0C31 ఱ TELUGU LETTER RRA — listed in the exemplars for the Telugu language

As discussed in Section 5.3, “5.4. Code Points Not Included” of [Proposal-Sinhala]:

Reason for Exclusion: Not in widespread use; not used in modern Telugu.

Combining Marks

Needed for NFD:—Where combining marks (such as U+0654  ٔ ) are excluded, but needed for decompositions of recommended characters, it was proposed to focus on the NFC format for Identifier_Type but documenting in UTS#39 that combining characters may be marked as Uncommon_Use even when they are in the NFD version of a modern language's exemplar characters.

The following text is proposed for UTS#39:

Where combining marks, such as U+3099  ゙  COMBINING KATAKANA-HIRAGANA VOICED SOUND MARK are only needed for NFD of recommended characters, they have been given Identifier_Type Uncommon_Use. Identifier systems that work with unnormalized text, or text in NFD may wish to add the full set of characters required in canonical decompositions.

Arabic Script combining marks:—Arabic combining marks are categorically excluded from domain names, see also RFC5564. The Internet Architecture Board [IAB] has issued a statement referencing this issue. Please also see the “Proposal for Arabic Script Root Zone LGR”, [Proposal-Arabic]. In consequence, their current assignment of Recommended has been specifically reviewed. The conclusion was to retain these as Recommended for default identifiers, based on deferring dual representation issues to the Confusables data defined for UTS#39.

In the context of this document, this affects the following:

• The major Arabic script combining marks U+064B  ً ..U+0652  ْ , U+0654  ٔ ..U+0655  ٕ , U+0670  ٰ . Recommend retaining recommended based on discussion. (See also the general discussion for "Combining Marks" above.)

Uppercase Characters

Uppercase characters must share the Identifier_Type of their lowercase equivalent. This is to ensure that default identifiers do not change validity if case mapped. Proposed Identifier_Type values included here match that of their lowercase equivalents. In addition, it is recommended that an invariance test be created to automatically verify the relation between Identifier_Type for lowercase and uppercase characters. Because uppercase characters were not independently evaluated, their table entries do not cite a reference containing source information attesting use.

Native Digits

Not all communities use the native digits encoded for their scripts equally in everyday situations. Where their use is not preferred in that context, native digit sets are excluded from the [RefLGR]. They are tagged here with Identifier_Type Proposed:Uncommon_Use and comments indicate their lack of common use. In cases where native digits are clearly historical or obsolete, Proposed:Obsolete might be more appropriate. However, no such determination has been made here.

Tibetan Script

There are some issues that render the Tibetan script problematic for inclusion in default identifiers. One is that Tibetan employs vertical stacks that may not render properly in address or status bars and similar places where identifiers are commonly displayed. This issue is most pronounced when the script is used for religious texts.

The other is the lack of a proper investigation of the script for modern use for specific characters of the Tibetan script in the context of identifiers.

A proposal to temporarily change the Tibetan Script to Limited_Use did not find a consensus. However, it is proposed to add a warning to UAX#31.

Proposed Language for UAX#31

Note: The Tibetan script is included in the list of recommended scripts because language and script are in widespread common use. However, implementers should be aware that the vertical stacking nature of Tibetan, unless constrained by additional rules, may lead to difficulties viewing an Identifier in user interface elements such as address or status bars. In addition, at the current time, the script has not been as carefully vetted or seen as much practical experience when deployed for identifiers in security-relevant contexts as is the case for the other recommended scripts.

Character Classes

The table in Section 4.1, “Character Classes” presents information about a number of sets collecting characters with different attributes or properties. For each set, a count of members is given. An optional arrow (→) indicates that only a smaller subset of the given set is actually found in this document. For example the notation 2332→0 for the set of characters tagged with RefLGR indicates that none of the characters in this document are part of the Reference LGR, which is as expected, as this document only discusses characters that are not included there.

Contributors

The excerpt that this proposal is based on was prepared by Asmus Freytag, based on data published in [RefLGR] and reference information from [MSR]. For details on the process and contributors to those projects, see [RefLGR-Overview], in particular, Section 1, “Overview” and Section 6, “Contributors”. Mark Davis, Michel Suignard, Roozbeh Pournader, Josh Hadley Ken Whistler, Robin Leroy and Markus Scherer have contributed feedback to this proposal.

Appendix: Code Point Sets

The following lists the sets of characters for each proposed Identifier_Type value. These can be used to import the values into property data or to convert them to Unicode set notations for additional comparisons. Elements of the sets are space separated and consist either of bare hex codes for single characters or a pair of hex codes separated by HYPHEN-MINUS to indicate a range.

Review_Needed()
Recommended(01F8-01F9 064B-0652 0654-0655 0670 0674 0682 0692 0694 06A5 06B6-06B7 06C5 06C7-06CA 06D3 06EE-06EF 06FF 17B2 1E0C-1E0D 1E24-1E25 1E3E-1E3F 1E5A-1E5B 1E92-1E93)
Proposed:Technical(0671)
Proposed:Obsolete(0690 090C 0C8C 0CB1 0D9E)
Proposed:Uncommon_Use(0114-0115 012C-012D 014E-014F 0156-0157 0162-0163 01D5-01DC 01DE-01E3 01EA-01ED 01F0 01F4-01F5 01FA-01FF 021E-021F 0226-0233 0400 040D 0450 045D 04C1-04C2 04CB-04CC 04DA-04DB 04EA-04ED 05B4 05F0-05F2 069B-069E 06A1 06A3 06B2 06B4 06B8-06B9 06BF 06FA-06FC 0750 0753-0755 0757-075F 0761 0764-0765 0769 076B-076D 0772-077D 08A1 08AA-08AC 0904 0929 0934 0944 0979-097A 098C 09D7 0A03 0A66-0A6F 0A72-0A73 0A81 0B0C 0B35 0B57 0B66-0B6F 0BD7 0BE6-0BEF 0C0C 0C31 0C55-0C56 0C66-0C6F 0CBC 0CC4 0CD5-0CD6 0D0C 0D29 0D66-0D6F 0D8E 0DE6-0DEF 0E4E 0EDE-0EDF 108B-108D 1090-1099 10F7-10F8 1207 1287 12AF 12F8-12FF 130F 131F 1347 135A 135D-135F 179D-179E 17A9 17D7 1E02-1E0B 1E0E-1E11 1E14-1E17 1E1C-1E1F 1E22-1E23 1E26-1E29 1E2E-1E35 1E38-1E3B 1E40-1E41 1E4C-1E59 1E5C-1E61 1E64-1E6B 1E6E-1E6F 1E78-1E8B 1E8E-1E91 1E94-1E99 2D80-2D96 A7B9 AB01-AB06 AB09-AB0E)