Unicode Conformance (was: Re: News of AFII...)

From: Kenneth Whistler (kenw@sybase.com)
Date: Tue Dec 22 1998 - 14:14:23 EST

Peter Constable wrote, in response to Berthold:

> You said, "...Unicode is not about composing characters by
> combining base and accent characters..." Au contraire! For an
> app to be conformant to Unicode, it must be able to work with
> such combinations. Quoting from page 2-9:
> "The Unicode Standard allows for the dynamic composition of
> accented forms. Combining characters used to create composite
> forms are productive."

I just want to clear up this misunderstanding about conformance to
the Unicode Standard.

Statements made in Chapter 2 of the standard are explanatory, intended
to give general information, but cannot be considered normative, and
do not define conformance to the standard. The above passage merely points
out the fact that the Unicode Standard includes combining characters
which can be used for dynamic composition.

It is Chapter 3 which contains the normative definition of conformance
to the standard. And the definitions and clauses there are carefully
stated so as not to require the support of any particular Unicode
character in order to be conformant. Just as a conformant application
is not *required* to support Tibetan to be conformant, so it is also
not *required* to support combining marks to be conformant. The key
concepts are interpreting characters as 16-bit values in accordance
with their definitions in the standard and not unknowingly trashing
16-bit values that are not interpreted. But no conformant Unicode
application has to interpret *all* Unicode values -- and that includes
the combining marks and all that they imply.

--Ken Whistler, Technical Director, Unicode, Inc.

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