xml-dev - ISO 10646 vs. Unicode in XML specs

["Paul W. Abrahams" <abrahams@valinet.com>]

The XML 1.0 spec says that a character is an atomic unit of
text as specified by ISO/IEC 10646.  However, that spec also
contains references to Unicode, and other XML specs also
refer to Unicode rather than to ISO/IEC 10646.

Of course, Unicode characters and ISO/IEC 10646 characters
are essentially, or perhaps exactly, in 1-1 correspondence.
The differences between the two standards vis-a-vis XML are
very subtle.   So what puzzles me is this: why do some
mentions of characters refer to ISO/IEC 10646 while others
refer to Unicode?   Putting it another way: were I writing
an XML-related spec, how would I decide which standard to
refer to?   Why don't all specs refer to Unicode rather than
to ISO/IEC 10646?

Paul Abrahams