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   Re: Irony heaped on irony

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  • From: Dan Connolly <connolly@w3.org>
  • To: David Megginson <david@megginson.com>
  • Date: Thu, 18 May 2000 10:43:38 -0500

David Megginson wrote:
> "Simon St.Laurent" <simonstl@simonstl.com> writes:
> > >I could move the schema, but that would break lots of _other_
> > >schemas, including the schema for schemas, which depend on it.
> > >
> > >Seems to me having something of mime type text/xml at the namespace
> > >URI for XML is not something we should have to apologise for.
> >
> > But it does seem that such a sweeping change in namespaces best practices
> > is worth an explanation or preferably a full-blown trip through the W3C
> > process, complete with working drafts.
> Tim and Simon are right.
> I will freely admit to not being aware of all of the minutiae of XML
> Schemas, but Henry's approach seems dead-on wrong to me.


As to Simon's point about process, the content of
http://www.w3.org/XML/1998/namespace is at the discretion of the W3C
it's not the result of any WG decision or Recommendation or anything.

As to Tim's point about the loss of the ability to get something
that works with a web browser, I agree that's unfortunate and
I expect to fix it. But I don't expect to remove the schema
in doing so.

>  The schema
> for schemas (and others) should reference an XML schema for the xml:
> Namespace using the xsi:schemaLocation attribute, as in
>   xsi:schemaLocation="http://www.w3.org/XML/1998/namespace
>                       http://www.w3.org/XML/Schemas/xmlschema-20000518.xsd"

Why? Why use schemaLocation when there's no need to?

> Please remove the schema from http://www.w3.org/XML/1998/namespace and
> put it somewhere else, then update the schema for schemas to follow
> this (better) practice.  This also has the advantage that users can
> refer to the specific version of the xml: schema that they want to use.

Hmm... issuing an address for each specific version of the schema
spec that we put on the web server is a reasonable idea, but
removing the schema from http://www.w3.org/XML/1998/namespace
removes the ability to use namespaces in schemas in the most
straightforward way.

> > We've spent over a year on XML-Dev and elsewhere explaining to the
> > world that Namespace URIs are just identifiers, battled over the
> > three/one namespaces for XHTML issue, and now it seems that
> > namespaces are indeed supposed to point to schemas.  (And packaging?
> > Is that gone?)
> I think that the XML Schema WG got it right with the
> xsi:schemaLocation attribute,

sure, it's a useful mechanism when you need it. But when
you don't need it, i.e. when the same party decides the
namespace name and the mechanism of publishing a
definition of it, why bother?

There was a urn attribute in HTML:
	<a href="http://..." urn="uuid:....">...</a>
but nobody bothered to use it and I think it didn't
survive into recent HTML versions.

> and I'm puzzled that they've failed to
> follow their own recommendation (that's small-r "recommendation", not
> "Recommendation").

use of schemaLocation is a MAY, not a SHOULD (i.e. not
a recommendation), I think... yes:

	"The xsi:schemaLocation and xsi:noNamespaceSchemaLocation
         attributes can be used in a document to provide hints as to the
         location of schema documents which may be used for validation."

	-- 2.6.3 xsi:schemaLocation, xsi:noNamespaceSchemaLocation

I think that on the contrary, it's important that the schema spec
leads the way toward the self-describing web.

Dan Connolly, W3C http://www.w3.org/People/Connolly/

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