Re: [Editorial Errata Reported] RFC4013 (1812)

[Jeffrey Hutzelman <jhutz@xxxxxxx>]

--On Wednesday, July 22, 2009 08:20:34 PM +0200 Simon Josefsson 
<simon@xxxxxxxxxxxxx> wrote:

> RFC Errata System <rfc-editor@xxxxxxxxxxxxxx> writes:
>
> > Section: 2.3
> >
> > Original Text
> > -------------
> > Section title is "Prohibited Output"
> >
> > Corrected Text
> > --------------
> > Section title should be "Prohibited Input"
> >
> > Notes
> > -----
> > Section 2.3 is talking about prohibited input, not prohibited output.
>
> I'm not sure about this -- compare RFC 3454 section 5, the terminology
> and design is about prohibiting code points in the _output_.
>
> Testing for code points in the _output_ may be semantically different
> from testing in the _input_.  Some other IDNA operation may modify code
> points into one of the prohibited _output_ code points.  See RFC 3454
> section 2, the map&normalize steps are taken before the prohibit step.

I agree with Simon here.  Prohibiting a code point in the output usually 
has the effect of making any input containing that code point result in a 
failure, but the point is that the _output_ will never contain that code 
point, even as the result of mapping and normalization -- the operation 
will fail instead.  This distinction was a conscious decision made in 
stringprep.

There is, however, an error -- the first sentence of this section does in 
fact claim to be specifying prohibited input characters.  The correct fix 
is to that text, not to the section title.

-- Jeff