Prohibiting mapping of PVALID characters

[Shawn Steele]

>>>>>
> The string is converted from the local character set into Unicode, if it is not already in Unicode.
> This conversion may also involve mapping some characters or sequences of characters 
> to others. However, such mapping MUST be limited to applying NFC for any character that
> has a type of PVALID, regardless of the local needs.
 >>>>

I think MUST is the right word.  

I know I'm not reading it as you intended, but read very literally there're a few problems:
 
> The string is converted from the local character set into Unicode, if it is not already in Unicode.  

Why bother discussing any other code pages, that just randomizes things?

> This conversion may also involve mapping some characters or sequences of characters 
> to others. However, such mapping MUST be limited to applying NFC for any character that
> has a type of PVALID, regardless of the local needs.

Opps,  "This conversion" would be the conversion "from the local character set into Unicode."  Mapping is interesting even if (especially if?) the originating string isn't in some other code page.  And for the second part, some systems (Apple), need to apply NFC, even if it was already in Unicode.

Maybe:

Some characters, or sequences of characters, in the input string may be mapped to others.  However, for any character that has a type of PVALID, such mapping MUST be limited to applying NFC, regardless of the local needs.

-Shawn