[Gen-art] LC review: draft-ietf-idnabis-bidi-06.txt

[Joel M. Halpern]

I have been selected as the General Area Review Team (Gen-ART)
reviewer for this draft (for background on Gen-ART, please see
http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html ).

Please resolve these comments along with any other Last Call comments
you may receive.

Document: draft-ietf-idnabis-bidi-06.txt
     Right-to-left scripts for IDNA
Reviewer: Joel M. Halpern
Review Date: 5-Oct-2009
IETF LC End Date: 14-Oct-2009
IESG Telechat date: N/A

Summary: This document is nearly ready for publication as a proposed 
standard.
There is one comment I have marked as Major.  I presume that the actual 
problem is not a defect in the intent of the spec, but a defect in this 
readers understanding.  Presuming such, I would ask that clarifying text 
be added.

Major issues:
In section 2, when describing the rules for what is allowed in labels, 
CS is allowed in labels.  It is not allowed to start RTL labels.  This 
looks fine, until I realized that CS includes ".", which I am pretty 
sure is not allowed in a label.
This gets further complicated in section 3, when talking about "The 
Character Trouping requirement", the text talks about "Delimiterchars" 
being CS, WS, or ON.  A parenthetical then says "They are not allowed in 
domain labels."
Since the normative text said that CS is allowed, there seems to be a 
problem.

Minor issues:
Rule 6 in section 2 talks about the requirements on the termination of 
an LTR (left-to-right) label.  This requirement is much tighter than 
just "don't end with an RTL character", since rule 5 already said "don't 
use any RTL characters."
However, the non-normative introductory text says roughly that this 
document does not put constraints on labels which do not use RTL characters.
My guess, as a person who is neither a DNS expert nor a Unicode expert, 
is that rules 6 is not a new rule.
If rule 6 is equivalent to existing rules in other documents, shouldn't 
there be an explanation of the fact that it is a restatement of existing 
rules?  If it is not just a restatement, then how can you get away with 
it in this document?

At the end of section 2, there is a reference to LDH-labels.  That is 
the only occurrence of the string LDH in the document.  I presume it is 
a typo for something?



Nits/editorial comments: