PRI #473: Unicode 15.1 Alpha Review

Background Document

Date: February 7, 2023

This document provides background material for the alpha review period for Unicode 15.1.

Alpha review is for early review and comment on the repertoire proposed for eventual publication in Unicode 15.1. As a reminder, during alpha review the repertoire is reasonably mature and stable, but is not yet completely locked down. Discussion regarding whether certain characters should be removed from the repertoire for publication is welcome. Character names and code point assignments are reasonably firm, but suggestions for improvement may still be entertained.

This early review is provided so that reviewers may consider the character repertoire issues prior to the start of beta review (currently scheduled to start in May, 2023). Once beta review begins, the repertoire, code points, and character names will all be locked down, and no longer be subject to changes.

How to Provide Feedback

Feedback for the alpha review period should be reported under this PRI #473, using the Unicode PRI comments form.

Data Files

During the alpha review period, some of the data files associated with the Unicode Character Database are also available for review at 15.1 alpha data files (Note: That link will only contain 15.1 alpha data files during the period of this alpha review. In the future it will contain draft data for future releases.) These files are not a complete set of data files yet—only a minimal set sufficient to prepare code charts. Caution: Please do not report missing data files or attempt to implement on the basis of these preliminary data files.

Code Charts

For ease of review, a set of alpha review charts have been prepared. These are accessible on a block-by-block basis for new characters proposed to be added for Unicode 15.1. See 15.1 delta charts.

Alpha review charts also show glyph changes specifically planned for Unicode 15.1. Proposed glyph changes are highlighted in blue, while new characters proposed for encoding in Unicode 15.1 are highlighted in yellow. Note that a significant number of the glyph changes are cosmetic only.

Notable Issues for Unicode 15.1

The following information is provided to help implementers prepare for some of the new features of Unicode 15.1. More information will be provided during the beta review period later this year.

New Ideographic Description Characters

Unicode 15.1 adds exactly five characters, for a total of 149,191 characters. The five new characters are Ideographic Description Characters (IDC) that are used in Ideographic Description Sequences (IDS), which represent a mechanism to visually describe the structure of ideographs. Three of the five new IDCs are binary operators that expect two arguments, and the remaining two new IDCs are unary operators that expect a single argument. Unary IDCs are new to the standard. Four of the five new IDCs fill the Ideographic Description Characters block, and the fifth is encoded at the very end of the CJK Strokes block.

Changes to CJKRadicals.txt

Implementers should take note that the second field of the CJKRadicals.txt data file can be blank if a corresponding radical does not exist in the CJK Radicals Supplement or Kangxi Radicals blocks, and that the third field may be a code point in any CJK Unified Ideographs block. These changes are the result of a syntax change to the informative kRSUnicode property to accommodate non-Chinese simplified radicals.

Addition of KP-source Glyphs to the Code Charts

The code charts for the CJK Unified Ideographs, CJK Unified Ideographs Extension A, and CJK Unified Ideographs Extension B blocks now include representative glyphs and source references for nearly 24,000 KP-source ideographs. Furthermore, the format of the code charts for the CJK Unified Ideographs block was updated to accommodate KP-source ideographs through the addition of a seventh column.

Emoji

No new emoji characters are planned for inclusion in Unicode 15.1. However, 118 new RGI emoji ZWJ sequences will be defined. During the alpha review period, the data files associated with emoji are also available for review at 15.1 alpha emoji data files (Note: That link will only contain 15.1 alpha emoji data files during the period of this alpha review. In the future it will contain draft data for future releases.)