Re: 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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