The basic concept documented in RFC 3402 DDDS algorithm.<div><span class="Apple-style-span" style="font-size: small;"><br></span></div><div><div><span class="Apple-style-span" style="font-family: 'times new roman'; font-size: 16px; "><pre style="word-wrap: break-word; white-space: pre-wrap; ">
<span class="Apple-style-span" style="font-size: small;"> The "i" flag indicates that the ERE matching SHALL be performed in a
case-insensitive fashion. Furthermore, any backref replacements MAY
be normalized to lower case when the "i" flag is given. This flag
has meaning only when both the Application and Database define a
character set where case insensitivity is valid</span>.</pre><pre style="word-wrap: break-word; white-space: pre-wrap; "><span class="Apple-style-span" style="font-size: small; color: rgb(51, 0, 0);"><span class="Apple-style-span" style="font-family: arial, helvetica, sans-serif;">This is the case when the chosen "x.--" means an "i" flag. This is not the case in the default "xn--" which is appropriate to support ASCII English and its possible caracter variations (ex. people foreign names, or foreign TM).</span></span></pre>
<pre style="word-wrap: break-word; white-space: pre-wrap; "><span class="Apple-style-span" style="color: rgb(51, 0, 0); font-family: arial; font-size: 13px;">jfc</span></pre><pre style="word-wrap: break-word; white-space: pre-wrap; ">
<span class="Apple-style-span" style="color: rgb(51, 0, 0); font-family: arial; font-size: 13px;"><br></span></pre><pre style="word-wrap: break-word; white-space: pre-wrap; "><br></pre></span><div class="gmail_quote">2009/3/6 Andrew Sullivan <span dir="ltr"><<a href="mailto:ajs@shinkuro.com">ajs@shinkuro.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im">On Fri, Mar 06, 2009 at 12:13:35PM -0500, John C Klensin wrote:<br>
<br>
> Well... A different way to look at this is that you can have all<br>
> of the case sensitivity, case-independent matching, and case<br>
> preservation you like in A-labels (as well as all other labels<br>
> that contain ASCII characters and maybe some others). IDNA does<br>
> not change the DNS.<br>
><br>
> A different way to state Erik's observation/suggestion would be<br>
> that, in IDNA-aware "slots" use (on registration, lookup,<br>
> storage in files, etc.) of anything but lower case needs to be<br>
> really strongly discouraged. That would imply that, in a given<br>
> "slot", the decision that IDNA can be used is a decision that<br>
> upper case is discouraged and violence may be done to it if it<br>
> appears. That is an application-layer design tradeoff, not a<br>
> statement about the DNS or a problem for 1034.<br>
<br>
</div>Actually, putting something like those two paragraphs together might<br>
make this idea rather more palatable. The more I think about this the<br>
more I think it has a certain appeal. It has slightly odd effects,<br>
because the traditional DNS case-preservation does go all the way<br>
through an IDNA-unaware application, and does _not_ go all the way<br>
through an IDNA-aware application. I am going to post a note to<br>
various dns weenies I know to try to get review of exactly this<br>
suggestion, because it does seem to be a way forward.<br>
<div class="im"><br>
> FWIW, 1034 could easily have contained a statement to the effect<br>
> that one MUST NOT take a label that one receives, map it through<br>
> a local (as in client-side) aliasing process and then look the<br>
> result up as if it were the original label. Presumably it was<br>
> omitted because, at the time, everyone thought it was obvious<br>
> (and they probably still do). But, if 1034 prohibits a strong<br>
> application and registration preference for lower-case native<br>
> character strings in IDNA, that implicit statement would<br>
> prohibit any IDNA mapping at all.<br>
<br>
</div>True.<br>
<div class="im"><br>
> We are doing a lot of that lately (Erik is certainly not the<br>
> only one).<br>
<br>
</div>I have the feeling that may be a charge of which I am guilty, yes.<br>
<br>
A<br>
<br>
--<br>
<div class="im">Andrew Sullivan<br>
<a href="mailto:ajs@shinkuro.com">ajs@shinkuro.com</a><br>
</div>Shinkuro, Inc.<br>
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