HYPHEN-MINUS

Chris Wright chris at ausregistry.com.au
Tue Jul 28 16:50:37 CEST 2009


Patrik,

Final follow up from our conversation yesterday, the point we were trying to make about hyphen-minus is as follows:

CONTEXTO for HYPHEN-MINUS

* Is similar to the section in the protocol disallowing consecutive hyphens in the third and fourth position (4.2.3.1 of protocol document)
* Is applied to Unicode labels; the encoded label does not violate host name syntax
* Has no context; the surrounding characters do not influence this test
 
I assume the rationale behind the prohibition of HYPHEN-MINUS at the beginning or end of a label is to carry across host name syntax restrictions into the Unicode label space. This appears to be attempting to achieve similar goals to section 4.2.3.1 in the protocol document by disallowing consecutive hyphens in the third and fourth positions. These two restrictions should appear in the same place.
 
To clear any confusion that may have arisen during limited discussion last week, the context rule is applied to the putative U-label, therefore the DNS and host name syntax restrictions do not apply (yet). Consider the label b[U+00FC]cher-. The output of this label through the punycode algorithm when appended with the ACE prefix gives gives xn--bcher--3ya. Note this label conforms to the host name syntax.
 
Thus for consistency, simplicity and clarity sake I propose the following:
 
In protocol change: 

4.2.3.1. Consecutive Hyphens
The Unicode string MUST NOT contain "--" (two consecutive hyphens) in the third and fourth character positions.
 
to
 
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).
 
And then remove the context rule from the tables document and return hyphen to PVALID status as with all other LDH characters

Thanks

Chris



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