I agree. Formally, either choice of definition could work (including or excluding U-Label). In terms of exposition, however, I think the simplest choice of terminology is that M-Label is anything that maps to a U-Label, including the identity mapping. So M-Label is a superset of U-Label.<br>
<br clear="all">Mark<br>
<br><br><div class="gmail_quote">On Wed, Apr 8, 2009 at 06:52, Eric Brunner-Williams <span dir="ltr"><<a href="mailto:ebw@abenaki.wabanaki.net">ebw@abenaki.wabanaki.net</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;">
that was my understanding, U is a subset of M.<br>
<div><div></div><div class="h5"><br>
Vint Cerf wrote:<br>
> won't making M-label a subset of U-label destroy an important property<br>
> of U-label as defined in IDNA2008?<br>
><br>
> Under IDNA2008 there is a one-to-one mapping of every U-label to A-<br>
> label and vice-versa, without any mapping.<br>
><br>
> M-label needs mapping to become a U-label and is thus a superset, I<br>
> believe.<br>
><br>
> Vint Cerf<br>
> Google<br>
> 1818 Library Street, Suite 400<br>
> Reston, VA 20190<br>
> 202-370-5637<br>
> <a href="mailto:vint@google.com">vint@google.com</a><br>
><br>
><br>
><br>
><br>
> On Apr 7, 2009, at 11:27 PM, YAO Jiankang wrote:<br>
><br>
><br>
>> ----- Original Message -----<br>
>> From: "Erik van der Poel" <<a href="mailto:erikv@google.com">erikv@google.com</a>><br>
>> To: "Paul Hoffman" <<a href="mailto:phoffman@imc.org">phoffman@imc.org</a>><br>
>> Cc: <<a href="mailto:idna-update@alvestrand.no">idna-update@alvestrand.no</a>>; "John C Klensin" <<a href="mailto:klensin@jck.com">klensin@jck.com</a>>;<br>
>> "Lisa Dusseault" <<a href="mailto:lisa.dusseault@gmail.com">lisa.dusseault@gmail.com</a>><br>
>> Sent: Wednesday, April 08, 2009 10:19 AM<br>
>> Subject: Re: M-label definition<br>
>><br>
>><br>
>><br>
>><br>
>>>>> "An M-label is a string that can be mapped into a<br>
>>>>> [valid] U-label. It may be a U-label, since those<br>
>>>>> trivially map into themselves. The category of U-label<br>
>>>>> is a proper subset of the category of M-label." (Mark<br>
>>>>> and others).<br>
>>>>><br>
>>> So, one possibility for M-label is to make it correspond to an<br>
>>> IDNA2003 "internationalized label", which would make the set of<br>
>>> M-labels a superset of U-labels. (The other possibility mentioned by<br>
>>> John is: [<set of U-labels> + <set of M-labels>] corresponds to <set<br>
>>> of IDNA2003 internationalized labels>.)<br>
>>><br>
>> another view:<br>
>><br>
>> [<set of U-labels> + <set of A-labels>] corresponds to <set of<br>
>> IDNA2003 internationalized labels> since IDNA2003 internationalized<br>
>> labels including all the forms of all valid IDNA2003<br>
>> internationalized labels.<br>
>><br>
>> M-label is a subset of U-label instead of superset. M-label is a<br>
>> special U-label which must do some mapping before being transformed<br>
>> into A-label or doing some lookup.<br>
>><br>
>><br>
>><br>
>> YAO Jiankang<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>><br>
>>> Does this make sense?<br>
>>><br>
>>> Erik<br>
>>><br>
>>> On Tue, Apr 7, 2009 at 5:31 PM, Paul Hoffman <<a href="mailto:phoffman@imc.org">phoffman@imc.org</a>><br>
>>> wrote:<br>
>>><br>
>>>> At 4:59 PM -0700 4/7/09, Lisa Dusseault wrote:<br>
>>>><br>
>>>>> I'm not certain a new term needs to be introduced. If we're talking<br>
>>>>> about a string that is invalid as a label, giving it that term<br>
>>>>> seems<br>
>>>>> to legitimize it. If we're talking about a string that may or may<br>
>>>>> not<br>
>>>>> be valid, that's just "a string"<br>
>>>>><br>
>>>> Good catch. John's second option was:<br>
>>>><br>
>>>><br>
>>>> When I supported it, I was thinking of it as "...a valid U-label",<br>
>>>> that is, without the "valid" being optional.<br>
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>>>><br>
>>>><br>
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>>><br>
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</div></div></blockquote></div><br>