ISO/IEC JTC 1/SC 2/WG 2

N2576

DATE: 2003-09-02
ISO/IEC JTC 1/SC 2/WG 2
Universal Multiple-Octet Coded Character Set (UCS) - ISO/IEC 10646
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Experts Contribution
Annex I for N2352R(Guideline for Handling of CJK Unification and/or DisUnification Error)
V.S. Umamaheswaran, T. K. Sato, T. L. Kobayashi
JTC 1.02.18 – ISO/IEC 10646

SC2/WG2 members and Liaison organizations
Electronic2

There are two kinds of errors that may be encountered related to coded CJK unified ideographs.
Case 1: to be unified error - Ideographs that should have been unified are assigned
separate code points.
Case 2: to be dis-unified error - Ideographs that should not have been unified are
unified and assigned a single code point. An example of this is the request from TCA in
document N2271.
When such errors are found, the following guidelines will be used by SC2/WG2 to deal with them.

I.1 Guideline for “to be unified” errors
A. The “to be unified” pair will be left dis-unified. Once a character is assigned a code
position in the standard, it will not be removed from the standard.
B. If necessary, an additional note may be added to an appropriate section in the standard.

I.2 Guideline for “to be dis-unified” errors
A. The ideographs to be dis-unified should be dis-unified and should be given separate code
positions as soon as possible (dis-unification in some sense, and character name change
in some sense also). These ideographs will have two separate glyphs and two separate
code positions. One of these ideographs will stay at its current encoded position. The
other one will have a new glyph and a new code position.
B. For the ideographs that are encoded in the BMP, the code charts in ISO/IEC 10646 arepresented in multiple columns, with possibly differing glyph shapes in each column. The
question of which glyph shall be used for the currently encoded ideograph will beresolved as follows. In the interest of synchronization between ISO/IEC 10646 and theUnicode standard, the ideograph with the glyph shape that is similar to the glyph that is
published in the “Unicode Book” will continue to be associated with its current code
position. For the ideographs outside the BMP, the glyph shape in ISO/IEC 10646 and theUnicode Book are identical and will be used with its current code position.
C. The dis-unified ideograph will have a glyph that is different from the one that retains thecurrent code position.
D. The net result will be an addition of new ideograph character and a correction and anadditional entry to the source reference table.

I.3 Discouragement of new dis-unification request
There is a possibility of “pure true dis-unification” request. This is almost like the new sourcecode separation request. This kind of request shall not be accepted disregarding thereasoning behind. Key difference between “TO BE DISUNIFIED” and “SHALL NOT BE
DISUNIFIED is as follows.
a. If character pair is non-cognate (means different character), those pair are TO BE
DISUNIFIED.
b. If character pair is cognate (means the same but different shape), those pair are
SHALL NOT BE UNIFIED.
Dis-unification request with reason of mis-application (over-application usually) of unification
rule should NOT be accepted due to the principle of M41.11 (see document N2404 / JTC
1/SC 2 N3568R).

For Further Discussion:
The above guidelines pertain to CJK Unified Ideographs. Similar guidelines are needed forcharacters of scripts other than CJK ideographs also. WG2 has entertained requests for disunification such as for Coptic from Greek following principles much along the same lines asabove. The only difference is that the ‘CJK Source References’ of CJK ideographs arereplaced with ‘character names’ for non-CJK Ideographs.
WG2 is requested to consider including some appropriately reworded guidelines for DisUnification of scripts other than CJK Unified Ideographs.