Subject: Re: [idn] SLC minutes

From: tedd <[email-masked]>
Date: Wed, 2 Jan 2002 10:08:00 -0500

Edmon et al:

I sent the following before, but it didn't appear in the idn. The 
following is a repost:

>This is the same as my thinking about LGC (Latin/Greek/Cyrillic) mapping,
>that is
>
><ALPHA><a><A><alpha>.example
>
>will be matched as
>
><a'><a'><a'><a'>.example
>
>So, we can really fulfil the spirit of Nameprep that: "The user should not
>be limited to only entering exactly the characters that might have been
>used, but to instead be able to enter characters that unambiguously
>[represents] the characters in the [perceived] host name.
>
>Perhaps this issue (what I call, Character Equivalence Mapping) will be
>discussed in other wgs but I just want to clarify what I meant during the
>SLC-IDN meeting and that I think it is important for the usability of
>multilingual domain names when they are deployed.
>
>Edmon

Yes, capital Omega is mapped to lower case Omega, but why?

I can understand that "A" has to be mapped to "a" to stop multiple 
registrations of the same name with different capitalizations. But 
why extend that "solution" to other code points? Clearly, the two 
glyphs (‡ v. w) are different enough to be noticed as being different 
-- so, the rational for excluding one (i.e., Character Equivalence 
Mapping) in favor of the other must have some grounds. But, what?

Furthermore, if one had to map one code point to another, then why 
didn't it go the other way? In other words, why wasn't the capital 
Omega kept and the lower case mapped to the upper case. After all, 
the capital Omega (‡) looks considerably different than all other 
glyphs -- where as the lower case Omega looks like a common to many 
languages "w". In addition, I would bet that the upper case Omega has 
better global recognition than its lower case brother. So, what's the 
point of Character Equivalence Mapping in this case?

tedd

-- 
http://sperling.com

---

From: "Edmon" <[email-masked]>
Date: Wed, 2 Jan 2002 15:03:45 -0500

Character Equivalence mapping is to deal with this issue:

A registrant registers a domain <ALPHA><BETA>.example
Advertises it to other people as their capital form AB.example
An end user will not know whether it was Greek or English and attempts to
access the site with ab.example and does not get to it.

With Character Equivalance mapping, this situation would not occur.  No
matter how a domain name is represented, it is always unique.

Bear in mind that this need to happen only during matching of names within
the DNS server.

A registrant can register <ALPHA><b>.example all they want.  This is the
misconception that I wanted to point out.  Character Equivalence mapping
does not prohibit mixed scripts.

Edmon

----- Original Message -----
From: "tedd" <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, January 02, 2002 10:08 AM
Subject: Re: [idn] SLC minutes

Edmon et al:

glyphs (? v. w) are different enough to be noticed as being different

the capital Omega (?) looks considerably different than all other

tedd

--
http://sperling.com

---

From: tedd <[email-masked]>
Date: Wed, 2 Jan 2002 18:20:47 -0500

Edmon:

I understand the problem -- I think I said that.

Now, the question is specifically: "Why is upper case <OMEGA> mapped 
to lower case <omega>?"

In other words, why is the Greek Letter Omega (upper case) mapped to 
omega (lower case)?

Instead, why wasn't the lower case omega mapped to upper case OMEGA? 
What was the reasoning behind setting that rule FOR that specific 
glyph? After all, if one is trying to "solve" a problem of unique 
domain names, then why map a glyph that IS unique to something like 
looks like so many other glyph's?

For example, what's the difference between "w.com" and "w.com"? Just 
take a look at lower case omega and tell me that it looks more 
distinctive from all the other "w"'s as the upper case omega does 
from all other glyph's. It simply doesn't.

If one was trying to solve a problem here, then I claim they didn't 
think it out. Now, point out where I'm wrong.

tedd

--- you posted

-- 
http://sperling.com

---

From: "Edmon" <[email-masked]>
Date: Wed, 2 Jan 2002 19:30:02 -0500

Hi Tedd,

----- Original Message -----
> Now, the question is specifically: "Why is upper case <OMEGA> mapped

It doesnt have to map to lower case.  It could map to upper case.  In fact
it could be mapped to some other code point too if that also needs to be
mapped.  We should however come up with a general strategy for Character
Equivalence mapping, for example, if there are 4 codepoints that could be
considered "equivalent" in perception then it will be mapped to the lowest
codepoint regardless whether it is uppercase or lowercase...

>
> For example, what's the difference between "w.com" and "w.com"?

I would argue that there is no difference perceptually.  That is the precise
reason why there needs to be character equivalence mapping.
Which means that all four codepoints: <W> <w> <OMEGA> <omega> should be
preped so that if a person registered:

<W><w><OMEGA><omega>.example

no matter how he represented it, (e.g. wwww.example) people will still be
able to get to the unique domain.

> think it out. Now, point out where I'm wrong.

You are not wrong.  We are talking about the same thing I think...

Edmon

---

From: John C Klensin <[email-masked]>
Date: Wed, 02 Jan 2002 20:10:52 -0500

Edmon, Tedd,

Please don't interpret what I'm about to say as encouragement to
go down the "character equivalence" path.  I think it leads to
madness, especially when used with the exact-matching (i.e.,
"get it exactly right or fail completely) procedures of the DNS.
But, just as an exercise, I would suggest that one might start
with three principles:

(i) From observation, when scripts have two cases, the
upper-case form is more likely to be highly stylized, and hence
differentiated from characters in other scripts, than the
lower-case one.  Hence, if one is going to adopt
stylization-based (glyph-distinction, if you prefer)
canonicalization rules, one is better off treating upper case as
the normal form, rather than lower case.

(ii) Many alphabets, especially western European
"Roman-character-based" ones, utilize diacritical marks to
distinguish sounds of accents associated with a single base
letter.  However, in many languages and dictionaries, a
character without a diacritical mark (or with one diacritical
and not another) is treated as different from that character
without the marking.    As a typographical convention that has
been established into language practice in some places, those
diacritical marks are often dropped when a lower-case character
carrying them is converted to upper case (in other languages and
scripts, or with other characters, they are not dropped).  But,
since they are sometimes dropped, lower-case characters (which
always carry the diacriticals when they are appropriate) provide
better differentiation than upper-case characters.  Hence, if
one is going to adopt differentiation-based canonicalization
rules with recognition of scripts that use diacriticals, one is
better off treating lower case as the normal form, rather than
upper case. 

(iii) There is a theory among scholars of writing systems that
_all_ modern alphabetic writing systems are derived from a
single Old Semitic writing system (which didn't have case
distinctions).  One fairly extreme way to accomplish  the sort
of "equivalence" you are looking for is to drop all attempts to
visually distinguish or match these characters (a process that
depends heavily on the fonts chosen for each, which contradicts
a Unicode design principle), map every character onto its
equivalent in that ancient script, and drop all other
differentiation.  Of course, doing this would eliminate much of
the goal of IDN work, as it would equivalence not only Roman-
and Greek-based scripts but those with, e.g.,  the scripts of
the middle east, Africa, and the Indian subcontinent.  Just
depends on how far one wants to go.

Note that the three possibilities above are contradictory and
fairly close to being mutually exclusive, although a strong case
can be made for each if one starts to do "character
equivalences".

     john

--On Wednesday, 02 January, 2002 19:30 -0500 Edmon
<[email-masked]> wrote:

>> Now, the question is specifically: "Why is upper case <OMEGA>
>> mapped to lower case <omega>?"
>> 
> 
> It doesnt have to map to lower case.  It could map to upper
> case.  In fact it could be mapped to some other code point too
> if that also needs to be mapped.  We should however come up
> with a general strategy for Character Equivalence mapping, for
> example, if there are 4 codepoints that could be considered
> "equivalent" in perception then it will be mapped to the lowest
> I would argue that there is no difference perceptually.  That
> is the precise reason why there needs to be character
> equivalence mapping. Which means that all four codepoints: <W>
> <w> <OMEGA> <omega> should be preped so that if a person
> registered:
> 
> no matter how he represented it, (e.g. wwww.example) people
> will still be able to get to the unique domain.
> 
>> 
>> If one was trying to solve a problem here, then I claim they
>> didn't think it out. Now, point out where I'm wrong.
>> 
>