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Re: [Minutes] 27 Jan 2003 TAG teleconf (httpRange-14, arch doc, IRIEverywhere-27, binaryXML-30, xmlProfiles-29)

From: Martin Duerst <duerst@w3.org>
Date: Mon, 17 Feb 2003 15:56:46 -0500
Message-Id: <4.2.0.58.J.20030206190027.045bb760@localhost>
To: Chris Lilley <chris@w3.org>
Cc: www-international@w3.org, www-tag@w3.org, Michel Suignard <michelsu@microsoft.com>

Hello Chris,

Continuing our discussion from a while ago.

At 03:57 03/02/06 +0100, Chris Lilley wrote:
>On Wednesday, February 5, 2003, 2:20:53 AM, Martin wrote:

>MD> XML is perfectly capable of representing FOO under
>MD> all circumstances without %-escapes, by using the characters directly,
>MD> or using numeric character references.
>
>Yes, it is perfectly capable. My point was that if IRI to URI was a
>one way trip then people would ignore the fact that the IRI could
>easily be represented in XML; *for portability* and * to be robust*
>to guard against any hex escaping that might happen later down the
>road they would always fully escape the IRI to start with.

I'm not sure at all that this will happen. In particular, for
namespaces, I don't expect people to rush for IRIs in the first
place (although that shouldn't be an argument for not thinking
things through carefully).

Also, I don't expect people to go for %ab%cd%ef just for the
satisfaction of having, in theory, used character FOO in their
namespace. They rather would use an ASCII transcription, let's
call it 'phoo' in our example. (but that again isn't an argument,
because it still means they don't use their own character FOO).

But what I think is most important is to point out the difference
between namespaces and 'your arbitrary Web address'.

Let's look at an example. The XSLT namespace is
'http://www.w3.org/1999/XSL/Transform'. This can also
be used, in a browser, to get to a page that says
"Someday a schema for XSL Transforms will live here"
(or "This is an XML namespace defined in the XSL Transformations
(XSLT) Version 1.0 specification." or "This is the XSLT namespace."
Which one you get depends on your browser's setting.

In addition, I can also use
http://wWw.w3.org/1999/XSL/Transform or
Http://www.w3.org/1999/XSL/Transform or any number of
other variants to get to the same page. I can even use
http://www.w3.org/1999/XSL/TRansform to get a 'multiple choices'
(and a while ago even this lead directly to a page). I can also use
http://www.w3.org/1999/XSL/Transform.html or
http://www.w3.org/1999/XSL/Transform.xsd or
http://www.w3.org/1999/XSL/Transform.txt and will get
a particular version of the text claiming that it's the
XSLT namespace. Of course, all these would be lies, only
http://www.w3.org/1999/XSL/Transform identifies the XSLT
namespace.

However, I have never heard any major complaints about their
XSL stylesheets not working because the above variants didn't
work. (I'm not saying nobody ever made such a mistake, but
people in the XML area are already pretty used to be careful
about upper/lower case).

Translating the above experiences to IRIs and our example,
I think it's not too difficult to expect that people will
understand that a namespace 'http://example.org/FOO'.
could also be written in XML as 'http://example.org/&#xfoo;',
if necessary, but not otherwise, and that when they describe
the namespace, they would say:

    The namespace for these elements/attributes is
       http://example.org/FOO
    If you are unable to enter FOO in your XML document, you
    can always use http://example.org/&#xfoo; instead.

In a browser, you could try
'http://example.org/FOO' or 'Http://example.org/FOO' or
'http://exaMple.org/FOO' or 'http://example.org/%ab%cd%ef'
or 'http://example.org/%AB%CD%EF'. Very old browsers
(Netscape/IE 4, older versions of Opera and Amaya)
would only work with the later two, and somewhat newer
browsers would work with all of them but display some
of the later two. Even newer browser would work with
all of them but display the first one. Please note that
analogous to this, you can get to the document(s) at
http://www.w3.org/1999/XSL/Transform by using
http://www.w3.org/%31%39%39%39/XSL/Transform, and on
some browsers even with
http://www.w%33.org/1999/XSL/Transform.


I very much think that the TAG finding on URI Equivalence
should state that resolution mechanisms have to guarantee
the equivalence of things such as ~ == %7e == %7E. This
is definitely true for http and other things I know, and
another good example that is resolution-related is
http://www.oasis-open.org/committees/entity/specs/cs-entity-xml-catalogs-1.0. 
html#sysid-norm
(which defines %-equivalence for characters outside the
URI repertoire, but not (it probably should) for non-
reserved characters in the URI repertoire).


So the overall conclusion would be:

- Codepoint-by-codepoint equivalence for namespaces and
   things with similar requirements (identifiers, fast processing).

- %-equivalence (i.e. ~ == %7e == %7E and similar) as a minimal
   requirement for resolution.


>MD> But even
>MD> in those cases, e.g. to tell somebody with an old email client
>MD> (like myself) how to use a particular namespace, it's always
>MD> possible to say: "well, just use xmlns:foo='http://example.org/&#xfoo;'."
>
>As long as i told you in an XML message and not, for example, plain
>text.

The important thing is not whether the message is XML or not,
even plain text can carry http://example.org/&#xfoo;, as this
message shows. The important thing is whether the that namespace
will be put into XML source or not.


Regards,   Martin.
Received on Monday, 17 February 2003 19:54:30 GMT

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