Unicode® Standard Annex #45

U-source Ideographs

Summary

This annex describes U-source ideographs as used by the Ideographic Research Group (IRG) in its CJK ideograph unification work.

Status

This document has been reviewed by Unicode members and other interested parties, and has been approved for publication by the Unicode Consortium. This is a stable document and may be used as reference material or cited as a normative reference by other specifications.

A Unicode Standard Annex (UAX) forms an integral part of the Unicode Standard, but is published online as a separate document. The Unicode Standard may require conformance to normative content in a Unicode Standard Annex, if so specified in the Conformance chapter of that version of the Unicode Standard. The version number of a UAX document corresponds to the version of the Unicode Standard of which it forms a part.

Please submit corrigenda and other comments with the online reporting form [Feedback]. Related information that is useful in understanding this annex is found in Unicode Standard Annex #41, “Common References for Unicode Standard Annexes.” For the latest version of the Unicode Standard, see [Unicode]. For a list of current Unicode Technical Reports, see [Reports]. For more information about versions of the Unicode Standard, see [Versions]. For any errata which may apply to this annex, see [Errata].

Contents

• 1Introduction
  • 1.1U-Source Identifier Prefixes
  • 1.2Classes of U-Source Ideographs
  • 1.3Data Files
  • 1.4Submission Process
• 2Text File Data
  • 2.1The Status Field
  • 2.2The Source Field
  • 2.3The Comments Field
  • 2.4The First Residual Stroke Field
  • 2.5The Ideographic Description Sequence (IDS) Field
• 3U-Source Additions
• References
• Acknowledgements
• Modifications

1Introduction

This annex describes U-source ideographs as used by theIdeographic Research Group (IRG) in its CJK ideograph unification work.

The IRG is a subgroup of ISO/IEC JTC 1/SC 2/WG 2 and has the formal responsibility of developing extensions to the encoded repertoires of unified CJK ideographs. The IRG consists of members of ISO/IEC contributors and liaison organizations, including many East Asian countries and the USA. The Unicode Consortium participates in this group as a liaison member of ISO. Each time the IRG begins the process of preparing a new CJK Unified Ideographs extension, IRG members submit a set of ideographs for potential inclusion in that extension. The IRG classifies these into sources, one for each member body, such as the J-source for Japan, the V-source for Vietnam, and so on.

The IRG U-source consists primarily of submissions from the Unicode Technical Committee (UTC). These include ideographs submitted by the UTC on behalf of the United Kingdom. The IRG U-source also includes ideographs encoded because they were originally submitted to the IRG by some other member body. Some of these are ideographs which were submittedto the UTC for consideration but were not submittedby the UTC to the IRG, and were later associated with a U-source. Others were left without a formal IRG source by changes made by the IRG in its source mappings; these were “adopted” by the UTC as explained below.

1.1U-Source Identifier Prefixes

Each ideograph in the IRG U-source has an identifier which consists of two or three letters (the prefix) followed by a hyphen and five zero-padded decimal digits. The prefixes currently used are listed below.

This UAX provides a formal reference to U-source ideographs, so that they may be referred to in other documents by their U-source identifiers. In many instances, it also provides a public record of ideographs which were submitted to the UTC for consideration.

1.2Classes of U-Source Ideographs

The U-source database consists of four classes of CJK ideograph:

1. Ideographs which have been submitted to the UTC as potential candidates for encoding. Note that not all such ideographs are actually suitable for encoding as a CJK Unified Ideograph. Those that are not have a status ofRejected.
2. Placeholder ideographs required to maintain continuity of U-source identifiers. Early versions of the U-source database allowed for the possibility of ideographs being withdrawn, generally because they had been added erroneously. Replacement ideographs were added in their place to keep any U-source identifier from being skipped. All such ideographs have a status ofRejected. (Ideographs are no longer withdrawn from the U-source database after they have been added.)
3. Placeholder ideographs required to provide encoded CJK Unified Ideographs with IRG source information. All CJK Unified Ideographs in ISO/IEC 10646 are required to have at least one source identifier. Changes to IRG source information, however, can leave a given ideograph without any such sources. In such cases, the ideograph is included in the U-source database to guarantee it has at least one source. Such ideographs are indicated by a source prefix ofUCI instead ofUTC. This practice is no longer followed and theUCI prefix is now obsolete. Formerly, changes to IRG source information may have restored non–U-source sources or provided new ones for such ideographs. In such cases, the ideograph retained theUCI prefix, but the encoded ideograph lost itskIRG_USource property value in the Unihan database and ISO/IEC 10646.
4. Ideographs submitted by the UK to the IRG via the UTC for Working Set 2015. These ideographs are included to provide a standard, stable source reference for IRG purposes. Such ideographs are indicated by a source prefix ofUK instead ofUTC. UK-submitted ideographs are no longer submitted through the UTC. No further ideographs with theUK prefix will be added. For more information about these ideographs, please seeUK-Source Ideographs.

1.3Data Files

The actual U-source data are found in the following three files:

• [Glyphs45], a PDF file showing the glyphs for the U-source ideographs. This document is a simple matrix with the representative glyph for a U-source ideograph and its identifier in each cell. The representative glyphs are drawn in a modern style, such as is used by the IRG in its unification work. The use of modern forms for some ideographs originally drawn in a seal style should not be taken as implying any mechanism for the inclusion of seal forms as a whole in [Unicode].
• [RSChart45], a PDF file providing a radical-stroke index for U-source ideographs. This index uses the glyphs found in the main glyph chart.
• [Data45], a text file containing information regarding the ideographs. A detailed description of this file can be found inSection 2,Text File Data.

1.4The Submission Process

Additions to the U-source may be proposed by submitting a document to the UTC. The document should contain adequate data to process the request. This includes:

• A representative glyph of sufficient detail to use in the production of a TrueType font and in IRG work. Requests with a large number of ideographs should include a TrueType font containing the representative glyphs.
• Metadata as found in the various U-source database fields.
• Sufficient evidence for inclusion in a proposal to the IRG.

Requests with insufficient data are likely to be declined.

2Text File Data

The text file consists of UTF-8 text. Each line consists of the following fields separated by semicolons.

0. The ideograph’s U-source identifier. This consists of the lettersUTC,UK, orUCI, followed by a hyphen and five zero-padded decimal digits, starting with 00001. Identifier numbers are not skipped, and are not reused. Identifier numbers are assigned sequentially. Ideographs whose prefix isUTC are either those submitted to the UTC for consideration or those included in the U-source database for placeholder purposes. Ideographs included to guarantee an IRG source reference have the prefixUCI.
1. A string indicating the ideograph’s current status. These are described below.
2. A Unicode code point. This field is generally empty. Its interpretation depends on the ideograph’s status and is documented below.
3. A radical-stroke index for the ideograph, as described in Unicode Standard Annex #38, “Unicode Han Database (Unihan)” [UAX38].
4. A KangXi dictionary index for the ideograph, as described in Unicode Standard Annex #38, “Unicode Han Database (Unihan)” [UAX38]. This field is no longer used and contains no data.
5. An Ideographic Description Sequence (IDS) for the ideograph, if one can be generated.
6. A string indicating the ideograph’s source and an optional index within the source.
7. General comments regarding the ideograph.
8. The ideograph’s total stroke count, as described in Unicode Standard Annex #38, “Unicode Han Database (Unihan)” [UAX38].
9. The ideograph’s first residual stroke.

2.1The Status Field

The status field reflects the ideograph’s current status. The value of this field can change over time. The possible values areComp,ExtA,ExtB,ExtC,ExtD,ExtE,ExtF,ExtG,ExtH,ExtI,FutureWS,NoAction,Rejected,URO,Variant,WS-2021, and strings matching the regular expressionsUTC-\d{5},UCI-\d{5}, andUK-\d{5}. New values may be added in the future and existing values removed.

A status ofComp means that the ideograph is encoded in the Unicode Standard as a compatibility ideograph. The value of the ideograph’s IDS field is U+303E 〾IDEOGRAPHIC VARIATION INDICATOR followed by the ideograph of which it is a compatibility variant. For example, UTC-00932 is encoded as U+FA26 都, which is a compatibility variant of U+90FD 都. UTC-00932 therefore has the IDS field value 〾都 (U+303E U+90FD).

A status ofVariant means that the ideograph is a variant of an ideograph encoded in the Unicode Standard. These variants are not limited to z-variants. Other variants include glyphs with components rearranged (for example, UTC-00344, which rearranges the components of U+69AB 榫 but is pronounced the same and means the same), simplified versions of encoded ideographs (for example UTC-00842), and ideographs which mean the same and are pronounced the same as encoded ideographs and have a sufficiently similar shape as to be easily mistaken for one another (for example UTC-00399). This is a deliberately less strict, if somewhat more subjective, standard than is used for unification work.

A status ofRejected means that the ideograph is not suitable for encoding as a CJK Unified Ideograph. An example here is UTC-00326, which is a nonce form specifically coined for use with Figure 18-9,Using the Ideographic Description Characters, in [Unicode] and to fill an empty slot in the U-source database. While the ideograph does have an intended meaning (“frog at the bottom of a well”), it isn’t suitable for encoding because of itsad hoc nature and lack of generalized use. The bulk of the ideographs with a status ofRejected are Wenlin-specific z-variants which should be represented (if at all), via a variation sequence defined by Wenlin, not by the UTC.

2.2The Source Field

The source field consists of source information, which consists of a source tag usually followed by a source-specific index string. Source tags and indices are separated by a space, and multiple source indices are separated by commas. Multiple sources are separated by asterisks.

Note that the sources listed here may not provide adequate evidence of use for IRG work. This is partly because ideographs listed here may not be suitable candidates for encoding, but also because IRG requirements for evidence have become increasingly stringent over time. Many of the ideographs in each of the sets encoded prior to Extension D do not have adequate evidence of use by current IRG standards.

The source tag may be a URI, in which case the index string is the date (year-month-day) when the URI was accessed. The source tag may also be a U-source identifier for cases where an ideograph was added to the U-source twice. The source tags beginning with a lowercasek correspond to fields within the Unihan database. Please consult Unicode Standard Annex #38, “Unicode Han Database (Unihan)” [UAX38], for information on these sources and the format and meaning of the index strings.

The remaining sources are listed below. The left column contains the source tag. The center column contains bibliographic information for the source. The third column contains a description of source index, if any. The description frequently includes a regular expression which the index matches; see Unicode Standard Annex #38, “Unicode Han Database (Unihan)” [UAX38], for more information.

2.3The Comments Field

The comments field is a general-purpose, unstructured field. It is generally empty. It can contain any Unicode character other than tabs, semicolons, and any line-break character. The purpose of this field is to provide any additional relevant information for an ideograph which is not included in any other fields. For example:

1. The comment field for UTC-00119 indicates why it is inappropriate for encoding.
2. The comment field for UTC-00595 clarifies its variation relationship to other ideographs.
3. The comment field for UTC-03215 contains akCantonese property value pending encoding.

A colon is used within the comments field as a separator for multiple comments.

2.4The First Residual Stroke Field

The first residual stroke is a number 1 through 5. It indicates the stroke type of the first-written stroke of the ideograph, exclusive of the radical. The first residual stroke is determined by the standard rules for writing CJKV ideographs. The five-stroke system is frequently encountered in East Asian sorting algorithms or input methods. In particular, it is used by the IRG in its unification work and is required for IRG submissions. The five strokes, with their Chinese names in parentheses, are listed below:

1. A horizontal stroke, such as 一 (橫, héng)
2. A vertical stroke, such as 丨 (豎, shù)
3. A downward right-to-left stroke, such as 丿 (撇, piě)
4. A dot or downward left-to-right stroke, such as 丶 (點, diǎn)
5. A hook, such as 乙 (折, zhé)

If an ideograph has no residual strokes, its first residual stroke value shall be set to 0 (zero).

2.5The Ideographic Description Sequence (IDS) Field

The Ideographic Description Sequence is of a form used by the IRG in its unification work. These IDSes follow the syntax defined in [Unicode] with two extensions to handle unrepresentable ideographs:

1. The IDS may be prefixed with U+303E 〾IDEOGRAPHIC VARIATION INDICATOR to mark the IDS as approximate and not exact.
2. The IRG defines a number of SGML-like entities for unencoded ideograph components. In IRG work, these are delimited by an ampersand (&) and semicolon (;). To maintain compatibility with the use of semicolons as field separators, they are delimited by square brackets ([ and]) in [Data45].

3U-Source Additions

The table below lists the U-source ideographs that were added in each version of the Unicode Standard, and those with identifier prefixes other thanUTC being highlighted for easier identification:

References

For references for this annex, see Unicode Standard Annex #41, “Common References for Unicode Standard Annexes.”

Acknowledgements

John H. Jenkins 井作恆 (RIP) was the author of the initial version of this annex, and served as the editor up through and including Version 27 for Unicode Version 15.0.0.

The UTC gratefully acknowledges the contributions of Eiso Chan, Henry Chan, Jaemin Chung, Lee Collins, Richard Cook, Jing Zuoheng, Ken Lunde, Ming Fan, William Nelson, Andrew West, and others to the U-source database.

Modifications

The following summarizes modifications from the previous revision of this annex.

Revision 29

• Reissued for Unicode 15.1.0.
• Removed John H. Jenkins as editor.
• Added Ken Lunde as editor.
• Changed theN,V,W, andX status values toFutureWS,Variant,Rejected, andNoAction, respectively.
• Added theExtI status value.
• Removed the now-obsoleteUK-2015 andWS-2017 status values.
• Inserted headers forSection 1.1,Section 1.2, andSection 1.3.
• Renumbered Section 1.1 asSection 1.4.
• AddedSection 3.
• Added a paragraph about the editor change to theAcknowledgements section.

Revision 28 being a proposed update, only changes between revisions 27 and 29 are noted here.

Previous revisions can be accessed with the “Previous Version” link in the header.

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