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Re: [idn] Tilde

Martin:

If, as you say, the mapping step is to avoid alternate representations and to erase case distinctions, then it has failed because it doesn't produced anything.

Why do you say that?

I say that with respect to the Tilde code point only. Nameprep, in prohibiting the code point, has neither avoided an alternate representation nor erased a case distinction -- it just said "No".

 The mapping clearly avoids alternate
representations and erases case distinctions. For example,
"www.LÖWIS.de" is treated as if it was "www.löwis.de".

I did not say that it didn't. I only said that it failed to do anything with respect to the Tilde except prohibit it -- and that statement is still true. For sake of argument, what's the alternate representation or case distinction problem presented by the Tilde?

So I fail to see that the mapping step has failed. It is very successful.

Mapping has proved to be useful for most code points -- I'm not claiming otherwise (other than with glyphs like the Omega). But, the current rules for which nameprep operates simply prohibits use of the Tilde. However, the reason for this is not founded in avoidance of alternate representations nor to erase case distinctions -- on the contrary, it appears arbitrary to me until someone provides me with a reason otherwise.

Now, if the tilde character is currently used in some fashion by behind the screens Internet techs, as Paul suggested, then I can understand why the tilde character is prohibited. 

I'd like to point out that it was always the intention, and is the
existing practice, that the IDNA RFCs are augmented by policies of the
registrars, which further constrain the set of characters that you can
use within a particular zone.

To my knowledge, none of the TLD registrars currently allows
registration of names which contain TILDE OPERATOR. So for
one-below-toplevel, the entire issue is irrelevant.

You are misinformed -- domains names, which include the TILDE OPERATOR, can be registered in both ".com" and ".net" TLD's and most likely other registrars as well.

Please tell me why mapping the tilde to the tilde operator wouldn't work. 

Because it would not matter. Consider a domain label "foo~", and assume
we are applying the "ToAscii" function, trying to generate the IDNA
version of the label. Please follow me though chapter 4 of RFC 3490 now.
Further assume that UseSTD3ASCIIRules is true.

1. If the sequence contains any code points outside the ASCII range
   (0..7F) then proceed to step 2, otherwise skip to step 3.

   No, this label does not contain any code points outside the ASCII
   range. So we proceed to step 3

3. If the UseSTD3ASCIIRules flag is set, then perform these checks:
   (a) Verify the absence of non-LDH ASCII code points; that is, the
         absence of 0..2C, 2E..2F, 3A..40, 5B..60, and 7B..7F.

   UseSTD3ASCIIRules is true, so we check. The label contains a
   non-LDH code point, so ToASCII fails.

Now, your proposal is that TILDE was mapped to TILDE OPERATOR.
That would have happened in step 2. However, according to the
specification, we have *skipped* step 2. Therefore, your mapping
approach wouldn't work, and ToASCII would fail.

Regards,
Martin


I don't see step #2.

If you're argument is "It won't work, because it doesn't", then I can't argue with that circular logic -- other than to say, I don't see any "valid" reason for its foundation.

Please realize that you are correct in your claim *only* because the tilde (code point 07E) is prohibited in step 3. So, by design, the process prohibits the character, but it does so for no specific purpose that I am aware -- and that's my point -- and has remained my unanswered question. So, specifically why does the "process" (nameprep, rule #3, "plan 9 from outer space", or whatever) prohibit code point 07E?

Also FYI, the character string "foo~" (where "~" is the TILDE OPERATOR) currently translates to xn--foo-ch2a, which can be registered as xn--foo-ch2a.com ("foo~.com). This domain is perfectly legal in both .com and .net TLD's -- in fact, it's currently open.

In summary, my claim is that if you can map uppercase "A" to lowercase "a", then you can map the TILDE to the TILDE OPERATOR.

The point here is to save keyboard real estate if: a) there is no reason for it to be prohibited; b) and if a simple mapping function (or whatever) can save a key without creating problems elsewhere; then why not?

tedd

PS: Whenever I wade into this list, I feel like a baby seal entering a pod of killer whales.
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