I believe that the simplest approach for compatibility, and for implementability, is to use the one I gave in a previous email, as replacement text for 5.3. That is, use the same structure as IDNA2003: toNFKC(toCaseFold(toNFKC(x))), then remove all default-ignorable characters but the joiners.<br>
<br>As I said, it appears that given the current consensus, we don't need to specially except eszett and sigma, but should we decide that we really need to preserve them, then we can do it in the following way.<br><ol>
<li>Find all the maximal substrings that do not contain the exceptional characters.</li><li>Convert each of those substrings with the above mapping.</li><li>Apply toNFC to the result<br></li></ol> (This is a logical statement; the implementation can be optimized.)<br>
<br>For example, take the (artificial) string:<br><div style="margin-left: 40px;"><B, full-width U, umlaut, eszett, e><br><br></div>You would map <B, full-width U, umlaut> to <b, u-umlaut>, skip the eszett, then map the <e> (no change). The result would be:<br>
<div style="margin-left: 40px;"><b, u-umlaut, eszett, e><br></div><br clear="all">Mark<br>
<br><br><div class="gmail_quote">On Tue, Mar 31, 2009 at 09:07, Vint Cerf <span dir="ltr"><<a href="mailto:vint@google.com">vint@google.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
What characters should be mapped into what other characters in a<br>
revised IDNA2008 specification?<br>
<br>
Can we describe succinctly and precisely what these mappings are? How?<br>
What should they be?<br>
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Vint Cerf<br>
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<a href="mailto:vint@google.com">vint@google.com</a><br>
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