Re: *Why* are precomposed characters required for "backward compatibility"?

From: Dan Oscarsson (
Date: Fri Jul 12 2002 - 07:29:08 EDT

>From: David Hopwood <>

>For all of these characters, use as a spacing diacritic is actually much
>less common than any of the other uses listed above. Even when they are used
>to represent accents, it is usually as a fallback representation of a combining
>accent, not as a true spacing accent.
>So, there would have been no practical problem with disunifying spacing
>circumflex, grave, and tilde from the above US-ASCII characters, so that the
>preferred representation of all spacing diacritics would have been the
>combining diacritic applied to U+0020.

Apart from the problems Kenneth Whistler mentioned.
You would get the same problems with the ISO 8859-1 spacing accents but
there are less people using them than with those in ASCII.
One problem is that some characters can be used as an accent and as
a normal base character, and some characters that Unicode defines
a decomposition of, is not a composed character in some countries.
So in some contexts is is wrong to decompose some characters that
could be ok to decompose in others.
That is one reason I prefer NFC as it do not decompose characters.


>> For a lot of text handling precomposed characters are much easier to
>> handle, especially when the combining character comes after instead of
>> before the base character.
>I thought you said approximately the opposite in relation to T.61 above :-)
Sorry, got the last part wrong in my haste. I meant it is easier when
the combining character comes before the base character.


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