WGLC: draft-faltstrom-5892bis-04.txt

Simon Josefsson simon at josefsson.org
Tue Apr 26 22:28:49 CEST 2011

"Jiankang Yao" <yaojk at cnnic.cn> writes:

> Dear colleagues,
> This message starts a two-week WGLC on the draft
> draft-faltstrom-5892bis-04.txt.


I support publication of a document to clarify IDNA2008's relationship
to Unicode 6.0 but I believe the content of the above document causes an
instability for U+19DA which can be avoided.  From my implementer's
point of view, it seems better to add U+19DA as PVALID in the
BackwardCompatible (G) category so that we have the property that
IDNA2008-Unicode5.2(X) = IDNA2008-Unicode6.0(X) for all strings X that
were permitted by IDNA2008-Unicode5.2.

The above document effectively forbids some strings that were permitted
before.  I believe this causes a perception of instability in the
algorithm.  It seems that permitting strings with this code point would
not cause any problem in practice.  To me that is a strong argument that
good algorithmical/implementation properties are more important than any
consideration for this particular code point.  If U+19DA would cause
operational difficulties, I would be more inclined towards forbidding
strings that contains it, but I haven't seen those arguments.

This has been brought up before by others, and I have merely been
convinced by that discussion.  I'm not trying to state this point as
anything original.  In particular, here are pointers to where Mark Davis
explains the point:


> Note: This draft is a document that updates an earlier RFC by stating
> nothing is to be updated.

That seems wrong.  Technically the document does not claim to update any
earlier RFC according to the document content (there is no 'Updates:'
header).  Could you clarify what you mean here?  Is the intention that
the document will be marked as Updating any earlier RFC or not?


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