Hyphen Restrictions

[Yoshiro YONEYA]

Dear Andrew and John,

Thank you for your quick response.  I'm clear now.  The reason why I 
raised this question was that two possible interpretation will cause 
interoperability problem between implementations.  And if the answer 
was later, it will cause big impact for IDNA-aware registries.

Regards,

-- 
Yoshiro YONEYA <yoshiro.yoneya at jprs.co.jp>

On Wed, 05 Jan 2011 01:46:36 -0500 John C Klensin <klensin at jck.com> wrote:

> 
> 
> --On Wednesday, January 05, 2011 15:18 +0900 Yoshiro YONEYA
> <yoshiro.yoneya at jprs.co.jp> wrote:
> 
> > Hi, all,
> > 
> > I need clarification of RFC5891 section 4.2.3.1, which says:
> > 
> > 4.2.3.1.  Hyphen Restrictions
> > 
> >    The Unicode string MUST NOT contain "--" (two consecutive
> > hyphens) in    the third and fourth character positions and
> > MUST NOT start or end    with a "-" (hyphen).
> > 
> > My question is that what "the third and fourth character
> > positions" means. Does it mean third and fourth octet from the
> > beginning of the string? For example:
> >   beginning of the string
> >     |
> >     v 1   2   3   4   5 <-- position of octet
> >     +---+---+---+---+---+
> >     | a | b | - | - | c |
> >     +---+---+---+---+---+
> >               ^   ^
> >               |   |
> >       two consecutive hyphens
> >...
> > 
> > My understanding for this restrictions is to preserve future
> > ACE prefix,  so I expect the answer for my question is former
> > one.  Is that right?
> 
> Yes
> 
>    john
> 
> 
> 
> 
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