Re: Katakana Extended-A?

> >Best to keep them in the same region as the other kana and bopomofo
> >blocks, etc. 2FE0..2FEF is free if sixteen characters are sufficient. 
> 
> I considered this at first, but then chose AAE0..AAFF for two reasons:
> 
> 1. there do appear to be more than sixteen characters to encode, and
> 2. http://www.unicode.org/alloc/CurrentAllocation.html describes 
> 2FE0..2FEF as being in the "Symbols Area" rather than the "General 
> Scripts Area."

There is nothing normative about these "areas", which are simply
designations of convenience to help in planning future
allocations. Note that 2C00..2DFF were once also part of the
"Symbols Area", but got reprogrammed to make space for encoding
Glagolitic, Coptic, Tifinagh, and extensions for Latin, Georgian,
Cyrillic, and Ethiopic.

However, it is known that there is another set of ideographic
description symbols, separate from the GB set encoded in 2FF0..2FFF,
so if the work to prepare a proposal for them ever gets completed,
2FE0..2FEF would be the most felicitous location for them to
be encoded.

As Benjamin indicates, the set of possible Katakana extensions also
appears to be more than 16 in number.

My own suggestion would be to use the space after Yi Radicals,
A4D0..A4FF, as a tentative location. But in any case, don't
sweat the exact location. Both the UTC and WG2 will be involved
in determining the actual encodings, should a proposal be
approved, and it is difficult to predict all the factors that
may be involved, or what might get approved for encoding before
your proposal is processed.

More important is to have a clean, well-documented proposal
that anticipates questions regarding decomposed versus precomposed
encoding for various combinations, and which is well-illustrated
with source examples.

--Ken