[idn] UTC recommendations on TC/SC

["Mark Davis" <mark@macchiato.com>]

The Unicode Technical Committee discussed this issue at meeting # 88 (Aug
14 - Aug 17). It recommends that Traditional-Simplified Chinese mapping not
be added to nameprep. In practice, such names will either all be in
traditional or all be simplified, thus normally having only two variants.
Thus the combinatorics are far less of a problem than in case mapping.

Clarifying text should be added to nameprep or other appropriate places, to
the effect that:

"Nameprep does not account for all of the variations that may occur or that
a user might expect. In particular, it will not account for choice of
spellings within the same language. Examples include "theater.com" vs.
"theatre.com", and "hemoglobin.com" vs. "h<U+00E6>moglobin.com" in American
vs. British English. Other examples are simplified Chinese spellings of
domain names (e.g., "<U+7EDF><U+4E00><U+7801>.com") vs. the equivalent
traditional Chinese spelling (resp. "<U+7D71><U+4E00><U+78BC>.com"). Nor
does nameprep account for language-specific equivalences such as
"aepfel.com" vs. "<U+00E4>pfel.com" (considered equivalent in German). For
such variants, multiple entries in zone files are recommended (such as
multiple registrations).

A different RFC, possibly not on the standards track, that discusses this in
more detail and provides guidelines for avoiding possibly-confusing
registrations could help people to understand the issues more clearly.

Mark Davis
Cathy Wissink