Re: [Lucid] FW: [[e-mail]: Re: Non-normalizable diacritics - new property]

[Andrew Sullivan <[e-mail]>]

On Thu, Mar 19, 2015 at 02:11:56AM +0000, Shawn Steele wrote:
> > At every level.  DNS names are exact-match.  Each identifier is unique.
> 
> For the machine, sure.  But if you throw in font weirdness and stuff, they become non-unique (to humans, not to machines) even in ASCII.  To make them be more unique one has to impose more rules, like "use a decent font", "lowercase everything".  Etc. 
> 

Yes.  That's what we're trying to understand.
 
> No, even all NFC or NFKC would be 100% unique to the machine

This is either tautologically true, or false.  Certainly we learned
with IDNA2003 that NFKC doesn't work, because while it's good for
increasing match probability the identifiers aren't stable.  So when
they're handed around through different environments, stuff happens
that is bad.

>  What I'm questioning is how unique is good enough?

Surely that's part of what we're trying to understand?

> By your analogy, adding a bunch of laws isn't necessarily going to stop crime.

Similarity in one dimension of an analogy doesn't entail similarity in
all of them: if there were no differences, it wouldn't be an analogy.
In this case, I think you have made a syllogistic mistake of
conflating "all" and "some", but I suspect the analogy is just a
distraction.  The point is merely that you cannot get from "this won't
ever be pefect" to "therefore we shouldn't even try" without a bunch
more premises.

> 
> I agree, with the caveat that we also balance the cost and the benefits/risk.  "As safe as possible" would argue against allowing both 0 and O or l and 1 to exist.  Almost nobody's argued that, so I don't think we want "As safe as possible".  
> 

And hence, a BoF to try to understand these issues.

> 
> We do seem to have some desire to be linguistic.  Otherwise Sharp-S and Greek didn't need touched.

We have people who want identifiers that work as useful things in
their writing systems.  And sharp-s and sigma seemed to be cases where
people were quite surprised, which means that the identifers are less
useful (because if the identifier system furnishes you with surprises,
that's inconvenient).  This new set of cases is in fact another set of
lurking surprises, which is why some of us are concerned about these
cases.

> I think the opinions of the computer scientists and users in marketing departments may differ greatly here.  Many users treat domain names more as a natural linguistic thing than a mathematical identifier.  Enough to sue over names.
>

I think speculating about the anthropololical facts here is going to
lead us to grief.  Let's stick with a domain of discourse we know
well.

Best regards,

A

-- 
Andrew Sullivan
[e-mail]