From: Kenneth Whistler (kenw@sybase.com)
Date: Fri Aug 29 2003 - 18:13:20 EDT
[ME]
> > I do not want to add a combining
> > Egyptological ring-thingy to Unicode. It is not a productive mark. A
> > capital and small letter i with a deformed dot is what's needed,
> > that's all.
[PK]
> I thought it was policy never to add new precomposed characters, however
> unproductive the combining marks are.
A character is "precomposed" if it is made up of parts which
can be *de*composed. Michael has said he does not want "to add
a combining Egyptological ring-thingy to Unicode". Without that
there is no part to *de*compose a "small letter i with a deformed
dot" into, so it would just stand on its own as another atomic
character -- exactly as Michael intends.
A diacritic mark might be productive or unproductive in a
graphological sense, but in either case, it only exists at
all in a character encoding *if* it is encoded. You can only
talk about an unproductive encoded combining mark if the
combining mark is present in the encoding.
There is no reason to decompose, in the *character* encoding,
every recurrent bit and piece of glyphs which *might* be
analyzed off graphically. Take a look at the Ethiopic script,
for example. Clearly the "butterfly", the "foot", and various
right side "flags", and so forth are analyzable, recurrent
bits of the system. But none of the Ethiopic characters are
treated as precomposed. Instead each syllable is treated as
an unanalyzed whole -- an atomic unit -- from the point of view
of the character encoding. Similar considerations apply to
other complex syllabic systems which are just encoded as
collections of atomic units, regardless of their graphic
structure. See the Unified Canadian Aboriginal Syllabics and
Yi, for example.
--Ken
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