Thanks Greg for your clarifications. I think your examples were
OK in pointing ot the problems of interoperability.
Is ISO 2022 for Japanese a subset of ISO 10646? If so, I have no
problem listing is as a "regional subset" of the "full" character set.
If you send japanese, you can send it in ISO 10646, and ISO 2022, but
the same implementation will show both. This is the interoperability
problem I'm trying to address.
The ISO 2022 encoding is not a subset of 10646. Actually 10646 can
be seen as the new 2022 scheme, where different character sets can
be chosen.
2022 is the definition of how to switch between character sets
registered with the ECMA registry. 2022 define the C0 C1 G0 G1 G2 G3
mechanisms , and each of the ECMA registered character sets then
have a code to be used with one or more of these switches.
The ECMA registered character sets then comprises a lot of
national ISO 646 7-bit variants, the ISO 8859 series, some ISO
6937 family character sets with non-spacing diacritics, some
16 bit character sets like the Japanese, the Chinese and the
Korean, and also control character sets.
10646 is one big character set, canonically defined as a 4-octet
character set, but with compaction forms to 1,2,or 3 octets and
with also a dynamic compaction form (1-4 octets).
I suppose that 10646 will have a designation code in the 2022
scheme, so they are able to interoperate in this way.
Keld