XHTML and the Three Namespaces

Marc.McDonald at Design-Intelligence.com Marc.McDonald at Design-Intelligence.com
Sat Sep 25 00:48:45 BST 1999

	Andrew Layman wrote (emphasis added):
> 6.	Schemas MAY be associated with namespaces, and MAY serve the role of
> defining the items in the namespace.
> 7.	IF a schema is associated with a namespace, there will be mechanisms
> for locating that schema given the namespace URI. (Note that this
> formulation expressly does not require that the URI of the schema is the
> same as the URI of the namespace.)
A lot of conditions for deciding that 3 namespaces will be used. As I
mentioned before, what happens if schema group decides NOT to use namespaces
and uses a technique similar to architectures, e.g. 
	<p xmlschema="strict"> not <strict:p>
What happens to all those XHTML documents with the 3 namespaces in them?

> I believe that the point of greatest misunderstanding here is the belief
> that point two requires conflating namespaces with schemas.  (I conclude
> this because several of my arguments in favor of point two have met with
> replies arguing not directly against point two, but instead arguing that
> namespaces and schemas are distinct.)
But point 2 (namespaces uniquely define elements with a single definition)
is a little convoluted since for most elements their syntax and semantics
are identical yet would be identified with a different namespace. Each
unique element has a single definition, but sets of 3 unique elements end up
with the same definition, e.g. strict:p, frameset:p, transitional:p.

The problem is that points 1-5 do not justify your proposed solution. Points
6&7 really don't match the language you used in justifying 3 namespaces:

"Another thing people would like is to be able to indicate in a document
> which set of rules the document is intended to conform to. This is done by
> giving each of the three grammars a namespace, and saying that the
> elements
> in each namespace are to be validated against the syntax in the DTD
> corresponding to that namespace."
There is no capability in XML 1.0 to validated sections of a document based
on their namespace. In fact the use of namespaces with validation is
problematic as has been discussed in this thread many times. Can you argue
for 3 namespaces without points 6 and 7?

And in considering HTML (4.0 I assume) documents versus XHTML documents:
"... Finally, it allows that existing HTML documents
> without any indication of namespaces, and consequently no namespace
> transitions, may be interpreted according to the broadest grammar"
There is no broadest grammer (or more exactly broadest DTD). Frameset has a
different element under the <html> element. You could construct a broadest
grammer by using <!ELEMENT html (head, (body | frame)> and other changes but
no such DTD exists. Having a single broadest grammer would argue for a
single namespace.

XHTML needs to:
1. Work with XML 1.0 (not XML + schemas, not XML 1.1).
2. An XML-formed (quoted attributes, no impicit end elements, ...) HTML 4.0
document should be interchangable with an XTHML document. In particular,
between browsers and XML processors. As HMTL 4.0 documents don't use a
single namespace yet alone 3, that would be a problem.
3. Not make decisions based on incomplete, unpublished work outside of its

Just use the XML techniques that everyone else uses.

Marc B. McDonald
Principal Software Scientist

Design Intelligence, Inc.
1111 Third Avenue, Suite 1500
Seattle, WA  98101
marc.mcdonald at design-intelligence.com
Ph: 206.343-7797
Fax: 206.343.7750


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