Re: [idn] (bias) summary of reordering discussion

[David Hopwood <david.hopwood@zetnet.co.uk>]

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Soobok Lee wrote:
> From: "David Hopwood" <david.hopwood@zetnet.co.uk>
> >
> > Make that an explicit objection - I think it's far too complicated to
> > justify the marginal benefits. Also, any changes or additions to
> > reordering would have disastrous consequences for name comparison, and
> > Soobok Lee's zq--/uq-- proposal does not fix this.
> 
> I expect you clarify this assertions with detailed examples soon.

The problem is this: how does an application that doesn't support the
latest version check whether a zq-- label is equivalent to a uq-- label?

For nameprep without reordering, an old application can perform matching
that will be correct provided that the inputs are nameprepped (i.e.
case folded NFC or NFKC), and this is sufficient for most purposes. In
your proposal, OTOH, it must just give up, because it has no information
about how characters are reordered in uq-- labels. I consider this to be
a fatal flaw in the proposal.

This flaw would not arise if reordering only applied to characters that
are assigned now (i.e. in Unicode 3.1), and new scripts were never
reordered. In that case the zq--/uq-- versioning wouldn't be needed.
However, I still don't think that reordering is worthwhile even in that
case.

- -- 
David Hopwood <david.hopwood@zetnet.co.uk>

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