Re: IRI guidance

On Fri, Apr 29, 2011 at 9:53 AM, Ivan Herman <ivan@w3.org> wrote:

>
> On Apr 29, 2011, at 15:42 , Pierre-Antoine Champin wrote:
>
> > On 04/29/2011 02:29 PM, Ivan Herman wrote:
> >>
> >> On Apr 29, 2011, at 15:17 , Pierre-Antoine Champin wrote:
> >> <snip/>
> >>>>>
> >>>>> [[
> >>>>> Note: RFC2397's mapping of IRIs to URIs does not alter "%25" or
> >>>>> punycoded domain names, which means that the IRIs
> >>>>> <http://伝言.example/R&D <http://xn--9oqp94l.example/R&D>> and <
> http://xn--9oqp94l.example/R%25D> will
> >>>>> both be transformed to the URI to <http://xn--9oqp94l.example/R%25D
> >.
> >>>>> RFC2397 section 3.2. "Converting URIs to IRIs" defines a function
> >>>>> which produces a single IRI for any URI. When minting IRIs for RDF,
> >>>>> it is encouraged to mint forms which can round trip to a URI form
> >>>>> and back.
> >>>>> ]]
> >>>>
> >>>> I think that the round-trip issue may not be clear (it is not 100%
> clear to me either:-).
> >>>
> >>> I, on the other hand, think the round-trip is a nice way to put it, and
> >>> quite well defined (although, see my concern #1 below).
> >>> An example of which IRI is produced from the URI above would help,
> though.
> >>>
> >>
> >> My understanding is that, concentrating on the IDN case, the
> >> IRI->punycode does not work in 100% cases, although the punycode->IRI
> >> does. So round-trip would then mean using the punycode.
> >
> > This is also my reading of RFC3987. Hence my concern #2 below.
> >
> >> Is this what we want?
> >
> > I would sure prefer <http://伝言.example/R&D<http://xn--9oqp94l.example/R&D>>
> to be the encouraged URI
> > rather than <http://xn--9oqp94l.example/R&D> .
>
> Absolutely. But that means referring to round-tripping is _not_ what we
> want there!
>

I think the notion of round-tripping only works if you stick with
percent-encoding and avoid punycode -- note that section 3.2 (URI to IRI)
doesn't decode the punycode-encoded IDN, it is only concerned with
unescaping %-encoded octets.  The only mapping guaranteed to produce a valid
URI in 3.1 is percent-encoding (although such a mapped URI may not meet
scheme-specific restrictions); punycoding is optional.  I don't think we
should ignore punycoding altogether, so maybe we should discard the sentence
about round-tripping and just go with Ivan's suggestion:

'The use of %-escaped characters or punycode encoded IDN-s are strongly
discouraged.'

-Alex



>
> Ivan
>
>
> >
> >  pa
> >
> >
> >>
> >> Ivan
> >>
> >>
> >>
> >>>> Why not adding something like
> >>>>
> >>>> 'In other words, the use of %-escaped characters or punycode encoded
> IDN-s are strongly discouraged.'
> >>>
> >>> It definitely would not hurt.
> >>>
> >>> I have three concerns, though:
> >>>
> >>> 1/ from what I read in RFC3987, section 3.2, the mapping from URI to
> IRI
> >>> is not completely specified (refering to section 6.1 of that same RFC)
> >>>
> >>> 2/ the URI-to-IRI described in section 3.2 does not eliminate punycode.
> >>> So <http://伝言.example/R&D <http://xn--9oqp94l.example/R&D>> is *not*
> round-trip-safe, but
> >>> <http://xn--9oqp94l.example/R&D> is.
> >>>
> >>> 3/ it should be made very clear that this is about minting IRIs from
> >>> scratch or from URIs, but *not* about converting IRIs (as IRIs that
> >>> would convert to the same URI are not consider equivalent).
> >>>
> >>> pa
> >>>
> >>>
> >>>>
> >>>> Ivan
> >>>>
> >>>>
> >>>>
> >>>>>
> >>>>>
> >>>>>> Cheers
> >>>>>>
> >>>>>> Ivan
> >>>>>>
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>> -Alex
> >>>>>>>
> >>>>>>> --
> >>>>>>> -ericP
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>> ----
> >>>>>> Ivan Herman, W3C Semantic Web Activity Lead
> >>>>>> Home: http://www.w3.org/People/Ivan/
> >>>>>> mobile: +31-641044153
> >>>>>> PGP Key: http://www.ivan-herman.net/pgpkey.html
> >>>>>> FOAF: http://www.ivan-herman.net/foaf.rdf
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> --
> >>>>> -ericP
> >>>>
> >>>>
> >>>> ----
> >>>> Ivan Herman, W3C Semantic Web Activity Lead
> >>>> Home: http://www.w3.org/People/Ivan/
> >>>> mobile: +31-641044153
> >>>> PGP Key: http://www.ivan-herman.net/pgpkey.html
> >>>> FOAF: http://www.ivan-herman.net/foaf.rdf
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>
> >>
> >> ----
> >> Ivan Herman, W3C Semantic Web Activity Lead
> >> Home: http://www.w3.org/People/Ivan/
> >> mobile: +31-641044153
> >> PGP Key: http://www.ivan-herman.net/pgpkey.html
> >> FOAF: http://www.ivan-herman.net/foaf.rdf
> >>
> >>
> >>
> >>
> >>
> >
>
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>
>
>
>
>