Dear ISO/IEC JTC 1/SC 22/WG 21/SG 16,

As I mentioned during the 2024-02-07 meeting, the alpha review period has begun for Unicode Version 16.0, slated for release later this year.

See the blog post https://blog.unicode.org/2024/02/unicode-160-alpha-review-opens-for.html and the PRI background document https://www.unicode.org/review/pri497/pri497-background.html.

As mentioned in the PRI background document, alpha review is for early review and comment on the repertoire proposed for eventual publication in Unicode 16.0.

In particular, this is your last chance to propose corrections to character names, which show up in C++ via named-universal-character.

Some aspects of the répertoire have direct implications on properties and algorithms; this is especially the case when it comes to Normalization Forms.

In particular, in Unicode 16.0, some characters are encoded with decompositions that interact with each other in novel ways. It is important to note that there is no change to the normalization algorithm: a straightforward implementation of normalization as described in the Unicode Standard for decades will handle these new characters fine. However, for some optimized implementations of normalization, these characters may constitute new edge cases. See https://www.unicode.org/review/pri497/pri497-background.html, under Normalization: Important Novel Behavior.

Implementers of normalization (which includes implementers of C++23 by [lex.name] paragraph 1) should check that their implementation works with the draft 16.0α data files, and that it passes the conformance tests in the associated NormalizationTest.txt.

Of course, while they should get a head start on ironing out potential issues, implementers should not actually release a 16.0α normalizer, nor even a 16.0β normalizer later this year; only after final publication in September should products or implementations be released based on 16.0 data files.

Best regards,

Robin Leroy