xmlns in XHTML

S

Saqib Ali

Hello All,

I am using Norman Walsh's XSLTs to transform some DocBook XML content
to HTML.

However I noticed that Norman Walsh's DocBook XSLT includes the
following
tag in the transformed document:
<meta xmlns="http://www.w3.org/1999/xhtml" ......

I think the XML Namespace can only be declared in <html/> tag for
e.g.:
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
is the correct way to declare the namespace.

<meta xmlns="http://www.w3.org/1999/xhtml" ...... is what Norman
Walsh's
XSLT produced, which I think is incorrect. I might be wrong.

Before I submit a bug-report to OASIS, I just to make sure that I m
not missing something. Let me know if I am wrong about xmlns
declaration.

Here are some sample documents transformed from DocBook XML to HTML
using Norman's XSLTs: http://www.xml-dev.com/blog/#88



Thanks.
Saqib Ali
 
A

Andy Dingley

Before I submit a bug-report to OASIS, I just to make sure that I m
not missing something.
Click to expand...

Here's a clue - Norman Walsh _really_ knows what he's doing. Many,
many people have also used those stylesheets over and over. I'm not
saying there are no bugs left, but obvious ones get found quickly.
Let me know if I am wrong about xmlns
declaration.
Click to expand...

Yes.
 
S

Saqib Ali

Let me know if I am wrong about xmlns
Yes.
Click to expand...

Can you please be more specific as to where in the XHTML DTD it allows
the xmlns attribute to be in the <META /> TAG ???

I was looking at the XHTML DTD @ http://www.w3.org/TR/xhtml1/#dtds it
seems like xmlns attribute is only allowed in the <html /> TAG.

Can you please point me to the exact location in the DTD, which allows
xmlns attribute to be in the <meta /> tag.

Thanks.
In Peace,
Saqib Ali
http://validate.sf.net
 
D

Derek Harmon

Saqib Ali said:
Can you please be more specific as to where in the XHTML DTD it allows
the xmlns attribute to be in the <META /> TAG ???
I was looking at the XHTML DTD @ http://www.w3.org/TR/xhtml1/#dtds it
seems like xmlns attribute is only allowed in the <html /> TAG.
Click to expand...

Observe that the xmlns attribute on the html tag is FIXED. The inference
drawn from this is that all the child elements defined by the DTD must
belong to the same namespace URI, and no others.

The "XML with Namespaces" recommendation (on which XHTML
is based) was created to address this limitation. Inherent in this
recommendation is the freedom to declare namespaces anyplace.

The relationship between XHTML and other namespaces is described
in section 3.1.2 of the XHTML 1.0 recommendation,

http://www.w3.org/TR/2000/REC-xhtml1-20000126/#well-formed

If you must validate against a DTD, since DTDs are incapable of
supporting namespaces, then the XHTML produced by the Doc-
Book XSLT is not strictly conforming. This is due to a known
limitation of the DTD, rather than incongrueity with the XHTML
recommendation.

XHTML 1.1 includes informative XML Schemas, that accomodate
the broader use of XML namespace declarations.


Derek Harmon
 
N

Nick Kew

You may be talking at cross-purposes. XML namespace rules and DTD
validation rules are different beasts. XHTML, and particularly XHTML1.0,
applies the latter. So <meta xmlns... /> is fine by XML rules but
invalid by XHTML rules.

As for whether the stylesheets are in error - I'd have to spend more
time than I have now to determine whether the error lies there or in
the user. But in reply to Andy's point, Norman Walsh may know what
he's doing, but Saqib in no ignorant newbie either.
Observe that the xmlns attribute on the html tag is FIXED. The inference
drawn from this is that all the child elements defined by the DTD must
belong to the same namespace URI, and no others.
Click to expand...

What FIXED means is that it's implied in the <html> element even when
an author omits it. It doesn't prevent use of other default namespaces
through an xmlns attribute on a child element.
The "XML with Namespaces" recommendation (on which XHTML
is based) was created to address this limitation. Inherent in this
recommendation is the freedom to declare namespaces anyplace.

The relationship between XHTML and other namespaces is described
in section 3.1.2 of the XHTML 1.0 recommendation,

http://www.w3.org/TR/2000/REC-xhtml1-20000126/#well-formed
Click to expand...

This is a case of design by committee pulling in different and
mutually incompatible directions. The only way this actually works
is by defining new DTDs (such as XHTML+MATHML+SVG). Or by dropping
both validation and browser-compatibility.
If you must validate against a DTD, since DTDs are incapable of
supporting namespaces,
Click to expand...

Not strictly true, but we'll skip over that.
then the XHTML produced by the Doc-
Book XSLT is not strictly conforming.
Click to expand...

Neither is it valid if it generates xmlns declarations in the manner
described here.
XHTML 1.1 includes informative XML Schemas, that accomodate
the broader use of XML namespace declarations.
Click to expand...

XHTML 1.1 is a true exercise in futility. It gratuitously breaks
browser-compatibility, but offers nothing in return, beyond what
ad-hoc-XML gives us for free in terms of availability of processing
tools.

Conclusion: XML and HTML each has advantages. But mixing them
requires attention to detail that is often missing.
 
R

Richard Tobin

Saqib Ali said:
<meta xmlns="http://www.w3.org/1999/xhtml" ...... is what Norman
Walsh's XSLT produced, which I think is incorrect. I might be wrong.
Click to expand...

DTDs and namespaces don't work very well together, so it may well be
invalid according to the DTD, and you may just want to ignore that
fact.

Furthermore there may be some variation between XSLT processors as to
what xmlns declarations they output, so it's very hard to guarantee
output that matches a DTD.

However, looking at one of your examples, I'm baffled. The top-level
<html> element doesn't have an xmlns attribute. The #FIXED
declaration in the DTD will give it one when it's read back in again,
but the XSLT processor that generated it didn't know that. In fact,
it looks as if none of the XSLT output except the meta element was in
the XHTML namespace, and that's why it put the xmlns attribute on
the meta element.

The first thing I'd do is try using a different XSLT processor.
Then ask Norm.

-- Richard
 
S

Saqib Ali

The "XML with Namespaces" recommendation (on which XHTML
is based) was created to address this limitation. Inherent in this
recommendation is the freedom to declare namespaces anyplace.

The relationship between XHTML and other namespaces is described
in section 3.1.2 of the XHTML 1.0 recommendation,

http://www.w3.org/TR/2000/REC-xhtml1-20000126/#well-formed
Click to expand...

Derek,
Thank you very much. This is exactly what I was looking for. :)

In Peace,
Saqib Ali
http://validate.sf.net
 
R

Richard Tobin

Nick Kew said:
What FIXED means is that it's implied in the <html> element even when
an author omits it.
Click to expand...

*And* that the author may not supply any other value, unlike a plain default.

-- Richard
 
P

Patrick TJ McPhee

% (e-mail address removed) (Saqib Ali) wrote in message
%
% > Can you please point me to the exact location in the DTD, which allows
% > xmlns attribute to be in the <meta /> tag.
%
% It's not in the DTD - xmlns is "magic" (it's part of XML, not XHTML),
% so look at the XML TR instead

It's magic, but if you want to validate against a DTD, you've got to
include the xmlns* attributes, as well as having the prefix consistent
between the instance and the DTD.
 
A

Andy Dingley

It's magic, but if you want to validate against a DTD, you've got to
include the xmlns* attributes, as well as having the prefix consistent
between the instance and the DTD.
Click to expand...

Are there any well-known validators that work correctly for XHTML with
embedded elements from other namesapces ?

Is there even as yet an agreed notion of what "correct" means in this
case ? I know there's a certain lack of clarity(sic) in how close
XHTML is to being "vanilla" XML (for reasons of HTML legacyness). It's
easy to treat XHTML + (X-foo) as an XML document and validate it as
such, but a lot harder to take a "post HTML, App C aware" tool and
persuade it that your document is valid.
 

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