In message <9903021547.AA23518@unicode.org>
John Cowan <firstname.lastname@example.org> wrote:
> Kevin Bracey wrote:
> > Firstly, are characters in the Hangul Syllables block canonically
> > equivalent to their decomposed conjoining Jamo?
> Yes. This was nailed down in Unicode 2.1, not very readably to be
> sure, but there.
Yes, I found TR8 after that post. Sorry about that.
> Even though you have to pass through some compatibility
> equivalences to get there, the overall transformation between
> hangul and jamo is canonical.
But if you have to pass through a compatibility composition to get there,
it the Jamo->Hangul composition can't be canonical:
G A N J ------------> G A NJ ------------> GANJ
G A N J can't be canonically equivalent to GANJ, because if it were then
G A N J = GANJ ("=" denoting canonical equivalence)
and G A NJ = GANJ
hence G A N J = G A NJ
hence N J = NJ
but we've stated that N J is only compatibility equivalent to NJ.
So the process given in section 3.10's "Hangul Syllable Composition" will
only give you a syllable that's compatibility equivalent to the Jamo
sequence, if you actually do anything in stage 1.
The only loophole I can see in that argument is that I don't think I
could prove the assertion "A B = A C => B = C" used in the last step.
-- Kevin Bracey, Senior Software Engineer Acorn Computers Ltd Tel: +44 (0) 1223 725228 Acorn House, 645 Newmarket Road Fax: +44 (0) 1223 725328 Cambridge, CB5 8PB, United Kingdom WWW: http://www.acorn.co.uk/
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