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

From: Dan Oscarsson (
Date: Thu Jul 11 2002 - 09:22:48 EDT

>From: David Hopwood <>

>The only difficulty would have been if a pre-existing standard had supported
>both precomposed and decomposed encodings of the same combining mark. I don't
>think there are any such standards (other than Unicode as it is now), are

Yes. T.61 is still in use. It uses combining accents. One place where it
used is in X.500. It also have the nice way where the combining accent
comes before the base character making it easier to parse.

>(Obviously, an NFD-only Unicode would not have been an extension of ISO-8859-1.
>That wouldn't have been much of a loss; it would still have been an extension
>of US-ASCII.)

NFD should not be an extension of ASCII. There are several spacing
accents in ASCII
that should be decomposed just like the spacing accents in ISO 8859-1
are decomposed.
All or none spacing accents should be decomposed.

I could ask why are not precomposed characters preferred to be used, if
they exist?
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


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