APNG IDNS WG some very simple requirements. While we may not use it, I think it might be a good reference.
The system must
1. be compatible with current DNS servers, clients and protocols. 2. co-exists with current English domain name space. 3. provides a mechanism for DNS to adopt multilingual characters
4. retains compatibility with all existing Internet protocols (e.g. HTTP, SMTP, FTP etc)
-- Harald Tveit Alvestrand, EDB Maxware, Norway Harald.Alvestrand@xxxxxxxxxxxxxx