M-label definition

Vint Cerf vint at google.com
Wed Apr 8 11:10:38 CEST 2009


won't making M-label a subset of U-label destroy an important property  
of U-label as defined in IDNA2008?

Under IDNA2008 there is a one-to-one mapping of every U-label to A- 
label and vice-versa, without any mapping.

M-label needs mapping to become a U-label and is thus a superset, I  
believe.

Vint Cerf
Google
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vint at google.com




On Apr 7, 2009, at 11:27 PM, YAO Jiankang wrote:

>
> ----- Original Message -----
> From: "Erik van der Poel" <erikv at google.com>
> To: "Paul Hoffman" <phoffman at imc.org>
> Cc: <idna-update at alvestrand.no>; "John C Klensin" <klensin at jck.com>;  
> "Lisa Dusseault" <lisa.dusseault at gmail.com>
> Sent: Wednesday, April 08, 2009 10:19 AM
> Subject: Re: M-label definition
>
>
>
>>>> "An M-label is a string that can be mapped into a
>>>> [valid] U-label. It may be a U-label, since those
>>>> trivially map into themselves. The category of U-label
>>>> is a proper subset of the category of M-label." (Mark
>>>> and others).
>
>>
>> So, one possibility for M-label is to make it correspond to an
>> IDNA2003 "internationalized label", which would make the set of
>> M-labels a superset of U-labels. (The other possibility mentioned by
>> John is: [<set of U-labels> + <set of M-labels>] corresponds to <set
>> of IDNA2003 internationalized labels>.)
>
>
> another view:
>
> [<set of U-labels> + <set of A-labels>] corresponds to <set of  
> IDNA2003 internationalized labels> since IDNA2003 internationalized  
> labels including all the forms of all valid IDNA2003  
> internationalized labels.
>
> M-label is a subset of U-label instead of superset. M-label is a  
> special U-label which must do some mapping before being transformed  
> into A-label or doing some lookup.
>
>
>
> YAO Jiankang
>
>
>
>
>
>>
>> Does this make sense?
>>
>> Erik
>>
>> On Tue, Apr 7, 2009 at 5:31 PM, Paul Hoffman <phoffman at imc.org>  
>> wrote:
>>> At 4:59 PM -0700 4/7/09, Lisa Dusseault wrote:
>>>> I'm not certain a new term needs to be introduced. If we're talking
>>>> about a string that is invalid as a label, giving it that term  
>>>> seems
>>>> to legitimize it. If we're talking about a string that may or may  
>>>> not
>>>> be valid, that's just "a string"
>>>
>>> Good catch. John's second option was:
>>>
>
>>>
>>> When I supported it, I was thinking of it as "...a valid U-label",  
>>> that is, without the "valid" being optional.
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