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

From: James E. Agenbroad (jage@loc.gov)
Date: Wed Jul 10 2002 - 12:11:27 EDT


On Tue, 9 Jul 2002, Kenneth Whistler wrote:

> David Hopwood wrote:
>
> > Marco Cimarosti wrote:
>
> >
>
> > 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
> ^^^^^^^^^^^^^^
> /character
> > think there are any such standards (other than Unicode as it is now), are
> > there?
>
> Not to my knowledge.
>
> >
> >
>
> --Ken
>
> >
> > - --
> > David Hopwood <david.hopwood@zetnet.co.uk>
>
>
                                                  Wednesday, July 10, 2002
ISO 5426 - 1980, Extension of the Latin alphabet coded character set for
bibliographic interchange, and its similar US counterpart, ANSI Z39.64,
Extended Latin alphabet coded character set for bibliographic use
(ANSEL), do contain both separate codes for diacritics for use with any
letter (e.g. tilde, grave, cedilla, etc.) and codes for characters which
could have been further decomposed (L with stroke, O with stroke, D with
stroke (all with codes for both upper and lower case) etc.) but were not.
In the US libraries have used ANSEL since about 1968 because they needed
to support many different languages.
I have to agree with Ken that ISO 10646 and Unicode probably would not
have gotten this far if they had excluded all precomposed combinations.
     Regards,
          Jim Agenbroad ( jage@LOC.gov )
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