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Re: URI schemes and IRI deployment

From: Martin Duerst <duerst@w3.org>
Date: Tue, 29 Jun 2004 22:31:18 +0900
Message-Id: <>
To: "Williams, Stuart" <skw@hp.com>
Cc: public-iri@w3.org

Hello Stuart,

Just a quick answer, because I'm traveling.

At 11:56 04/06/29 +0100, Williams, Stuart wrote:

>I'd like to understand expectations wrt to IANA registered URI schemes
>following adoption of the IRI spec as an RFC and during deplyment of IRIs.
>Do they 'instantly' become IRI schemes too?

Yes, all of them in the sense that every URI is an IRI, at least.
And most of them to the extent that they allow %-encoding and either
require (e.g. urn, imap,...) or allow (e.g. http) the %-encoding
to be based on UTF-8.

>Will they require maintenance to allow the use of the expanded character set
>allowed by the generic IRI syntax?

Some of them will. The most prominent example: mailto:, which is
very restrictive in where it allows %-encoding, if at all.

>The IRI spec gives a generic syntax that allows a broader range of
>characters to be used identifiers, but each currently registered scheme is
>written from a URI perspective with the potential to narrow rather than
>broaden the range characters used in an identifier from those permissablein
>the URI spec.
>The IRI spec. has section on upgrade strategy (7.8) which speaks of
>upgrading of applications to handle IRI, but it does not appear to say
>anything about upgrading of URI scheme registrations.

What URI schemes might need upgrade or not can be deduced from
the exact definition of what's an IRI, which explicitly requires
that the result of the IRI->URI conversion has to be a legal URI.

>The identifier http://www.w3.org/People/d$BS(Bst

[sorry, my Japanese mailer will have garbled that]

>may be admissable under the
>generic IRI syntax, but is it a valid HTTP scheme IRI? And if so... what
>specification makes it admissable as an HTTP scheme IRI?

The IRI spec. If you take the above, and convert it to an URI,
you will get http://www.w3.org/People/d%C3%BCrst. The HTTP URI
spec says that this is a legal URI, so the one above is a legal IRI.
In this case, it's not only legal, it's actually dereferencable,
although the content at that location isn't terribly up to date,
and the exact URI would be http://www.w3.org/People/D%C3%BCrst,
but the server takes care of the casing issue.

You will also observe that if you put the URI in the address bar
in Opera, you'll get back the IRI. Other browsers may do something
similar, or may at least allow you to put in the IRI and get
to the actual page. (you have to be careful in the above example
because I also put in some redirects, e.g. for
http://www.w3.org/People/d%FCrst, the Latin-1-encoded version,
but you'll see when that happens because the redirects are
explicitly taking time.

>Simply, my question is... what is the transition plan for scheme
>registrations wrt to IRI deployment?

For many if not most, there is no need for a plan. For some,
such as http, it's mostly an issue of how people set up their
servers. For some, such as mailto:, some work may be appropriate,
but in that specific case, there have been quite a few discussions
about weather and how to internationalize the left hand side of an
email address, and that discussion hasn't yet been conclusive.
It seemed better to wait to see where that would lead before
upgrading mailto:.
For newly created URIs, if they follow the guidelines for new
URI schemes, they'll work with IRIs automatically.

>Apologies if you have answered this before... I have looked, but did not
>find anything relevant.

In the IRI spec, please look at 'applicability' very early on,
and then at the prose in the sections on syntax and on IRI->URI
mapping. There is no such thing as e.g. a 'catalog of schemes
that need upgrading', because after all, the IRI draft is a
generic document.

Regards,    Martin.
Received on Tuesday, 29 June 2004 09:31:49 UTC

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