L2/03-090

Title: Compatibility Decompositions for Squared abbreviations
Author: Asmus Freytag
Action: Input to UTC


Unicode 4.0 adds a few more squared Latin abbreviations that brought with  
them new compatibility decompositions. This document is intended as a  
resource for UTC in reviewing the proposed decompositions.

Usually, we spell out the glyph for the 'squared' Latin Abbreviations when  
we do our decomposition. Sometimes the capitalization of the compatibility  
character is different from the common appearance of the abbreviation in  
normal text. This can lead to issues with decompositions.

The following is a brief rundown of past and new characters that had glyph  
or decomposition issues.

Two letterlike characters TEL and now FAX, are considered squared  
abbreviations, even though they are not named that way and don't occur in  
the CJK Compatibility block.

2121 TEL

glyph and decomposition changed from
    <super> T  E  L
to
    T E L

in Unicode 3.0

2222 FAX

proposed decomposition is
    F A X

In both cases, presumably, we intend that other capitalizations can be  
unified with these (eg. Tel or Tel. etc.)

32CF LTD  (glyph is in caps)

prosed decomp
    L T D

The all-caps use is not the most common. If we ever get a Ltd or Ltd.  
compat characters (that we feel we need to support) we may need to decide  
whether we should clone the character. That's what we did for

339E km

and

33CE KM

however, in the latter case the SI has specific rules for capitalization  
which are lacking for the commercial abbreviation.

A similiar issue holde for

3XXX PTE (glyph is in caps)

Both LTD and PTE were added to accommodate the DPRK.


3396 ml

This has 2113 as the 'l' in glyph and decomposition. However, the glyph  
changed from Ml to ml between 1.0 and 2.0. Curiously, the glyph for this  
character in MS Mincho is still Ml, which is the reason that it is wrong in  
the 4.0 beta charts. (in the SI system 'M' is Mega, and 'm' is milli. Even  
though 2113 is not (or no longer?) an SI symbol for liter, Ml with capital  
M would presumably mean Megaliter, an unusual quantity.

It's speculation whether the glyphs for MS Mincho were designed based on  
Unicode 1.0, or whether there really is a strong tradition for using a  
capital M.

33D7 pH

has a historic decomposition as PH, which is unchanged, even though the  
glyph was changed from PH in 1.0 to pH in 2.0 and has remained that way and  
is now pH in Mincho.

Since we did change the decomposition for TEL, the retention of this  
unusual decomposition in 2.0 should be considered a defect.