XHTML & Schemas

Paul Prescod paul at prescod.net
Thu Sep 2 19:06:38 BST 1999

Oren Ben-Kiki wrote:
> For example, you yourself have said:
> > By this reasoning, it doesn't matter how many different name-space
> > prefixes XHTML uses because *none of them* give you a way to know that
> > what you are processing is in fact an XHTML document (or XHTML-specific
> > element). Rather, the binding between documents and their *governing
> > semantic definitions* (e.g., schemas, architectures, etc.) must be
> > provided by some other mechanism. In the absence of a generalized
> > mechanism for doing this binding, it can only be done in documentation
> > of the semantics.
> Which, is, of course, a direct contradiction of thee above. 

Do I write like that?? Don't answer that question! The truth is that
that's Eliot's writing. I forwarded it to the list for him.

The schema specification does in fact say that schemas are triggered by

> Their example even shows the namespace URI as pointing to the schema - but
> another paragraph in the same spec indicates that the processor does not
> necessarily uses this URI to download the schema. At any rate...

The idea of having namespace URIs be triggers is logical and (I thought)
uncontroversial. Fetching schemas THROUGH namespace URIs is in fact very
controversial. But those are different issues.

> At any rate, as you've pointed out, the XSchema approach _requires_ the
> XHTML use of three namespaces. The fact that I don't like it - and that many
> others don't like it - is besides the point. If people want to have a single
> namespace for XHTML, they should first go and re-write the above paragraph
> in the XSchema draft. Right?

What would you rewrite it to? Let's say you have three schemas for XHTML
on your hard drive or on the web. Let's say that you have a document
like this:

<P xmlns="http://www.w3.org/TR/XHTML">This is supposed to be loose.</P>
<P xmlns="http://www.w3.org/TR/XHTML">This is supposed to be strict.</P>

How would you select the schema to use for each?

I agree with you and David for the schema specification to say that
given a namespace URI the schema to fetch is hard-wired. But that wasn't
my point. It was the opposite: there must be AT LEAST enough information
in the document to *allow* the namespace processor to select a schema.
If yours chooses to select a different one than mine then that is fine.

If we do not put enough information in our documents for schema
processors to know that we really meant for the data to be strict then
they wil have to presume loose...right?

 Paul Prescod

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