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Re: namespace question

From: William J. Edney <bedney@technicalpursuit.com>
Date: Fri, 18 Jul 2008 13:35:21 -0600
Cc: www-forms@w3.org, www-forms-request@w3.org
Message-Id: <2B222A31-895C-413A-84EF-834442A78328@technicalpursuit.com>
To: "Klotz, Leigh" <Leigh.Klotz@xerox.com>
All -

This is, IMHO, a really bad idea. Here's a not-so-uncommon use case:

Assume I have a the following content in file foo.xml:

<employees>
	<employee...>
		....
	</employee>
</employees>

Now, assume further that I have the following XHTML document:

<html xmlns="http://www.w3.org/1999/xhtml">

<head>
	<xf:model xmlns:xf="http://www.w3.org/2002/xforms">
		<xf:instance>
			<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  
href="foo.xml"/>
		</xf:instance>
	</xf:model>
</head>

<body>....</body>
</html>

In this case, the burden of making sure that the <employees> element  
gets an 'xmlns=""' falls to the XInclude processor. Here's the  
relevant section from the XInclude specification, 2nd Ed., regarding  
'Infoset merging':


4.5.4 Namespace Fixup

The in-scope namespaces property ensures that namespace scope is  
preserved through inclusion. However, after inclusion, the namespace  
attributes property might not provide the full list of namespace  
declarations necessary to interpret qualified names in attribute or  
element content in the result. It is therefore not recommended that  
XInclude processors expose namespace attributes in the result. If this  
is unavoidable, the implementation may add attribute information items  
to the namespace attributes property in order to approximate the  
information conveyed by in-scope namespaces.


The behavior proposed here would force the XInclude processor to use  
the mechanism described after "If this is unavoidable..." and, given  
that the specification here says MAY not MUST, its not a required  
behavior for the XInclude processor. And this wouldn't be the only  
place where not explictly producing namespace information is dangerous.

As the person who reported a bug in Mozilla's XML Serializer that was  
improperly serializing null namespaces (https://bugzilla.mozilla.org/show_bug.cgi?id=301260 
  - finally fixed in Mozilla 1.9 / FF 3.0), this whole thing smells  
really bad to me and violates Jon Postel's Robustness Principle (http://en.wikipedia.org/wiki/Robustness_Principle 
).

Cheers,

- Bill

On Jul 18, 2008, at 11:33 AM, Klotz, Leigh wrote:

> Here's my take:  Omitting xmlns="" on the root element has another  
> advantage, in that it makes it easier for non-namespace-aware  
> services to accept the posted XML. The attribute submission/ 
> @includenamespaceprefixes was added to facilitate interoperation  
> with services such as those that use DTD validation.  Since xmlns=""  
> doesn't add anything to the party for namespace-aware applications,  
> and might startly DTD applications, leaving it off seems a good plan.
> Leigh.
>
> From: www-forms-request@w3.org [mailto:www-forms-request@w3.org] On  
> Behalf Of Nick_Van_den_Bleeken@inventivegroup.com
> Sent: Thursday, July 17, 2008 11:40 PM
> To: Aaron Reed
> Cc: www-forms@w3.org; www-forms-request@w3.org
> Subject: Re: namespace question
>
>
> Hi Aaron,
>
> When the root element of the instance has a default  namespace  
> declaration with the attribute value of the empty string (xmlns=""),  
> you may omit  this default namespace declaration on the root element  
> that is serialized (it is even preferable to do so, but it is not an  
> error to xmlns="" on the root element).
>
> See [1] for more information and more specific the text : "The  
> attribute value in a default namespace declaration MAY be empty.  
> This has the same effect, within the scope of the declaration, of  
> there being no default namespace."
>
> If you have any further questions please feel free to send an e-mail  
> to the list. And we will do our best to help you ;)
>
> Regards,
>
> Nick Van den Bleeken  -  Research & Development Manager
> Inventive Designers
> Phone: +32 - 3 - 8210170
> Fax: +32 - 3 - 8210171
> Email: Nick_Van_den_Bleeken@inventivegroup.com
>
> 1: http://www.w3.org/TR/REC-xml-names/#defaulting
>
> www-forms-request@w3.org wrote on 07/17/2008 06:47:03 PM:
>
> >
> > Hi Nick,
> >
> > Yep, we know it is a bug in Firefox that the root namespace from the
> > host document is making into the submitted document as the default
> > namespace when the default namespace was given to be empty.  But  
> what
> > we'd like to know is whether a default empty namespace should be  
> placed
> > on the submitted document at all.  If the first default namespace  
> we see
> > is empty as we work our way up the tree, should we NOT output it and
> > from then on ignore the default namespace or should we output it?
> >
> > Thanks,
> > --Aaron
> >
> > Nick_Van_den_Bleeken@inventivegroup.com wrote:
> > >
> > > Hi Swithun,
> > >
> > > Your problem is a bug in Firefox, the default namespace of the  
> submitted
> > > instance should be the empty one. You have correctly specified  
> this on
> > > your in-line instance.
> > >
> > > I searched the Firefox XForms bugzilla database and found a bug  
> report
> > > for this problem https://bugzilla.mozilla.org/show_bug.cgi?id=445285 
> .
> > > You probably want to vote on this bug report.
> > >
> > > Regards,
> > >
> > > Nick Van den Bleeken  -  Research & Development Manager
> > > Inventive Designers
> > > Phone: +32 - 3 - 8210170
> > > Fax: +32 - 3 - 8210171
> > > Email: Nick_Van_den_Bleeken@inventivegroup.com
> > >
> > > www-forms-request@w3.org wrote on 07/11/2008 03:23:10 PM:
> > >
> > >  >
> > >  > Hello
> > >  >
> > >  > I have a small puzzling problem. I have an XForms document  
> where the
> > >  > default namespace is declared as so:
> > >  >
> > >  > <html xmlns="
> > > <http://www.w3.org/1999/xhtml>http://www.w3.org/1999/xhtml" ...
> > >  >
> > >  > (with all the other namespaces there too)
> > >  >
> > >  > Then, in one of the instances, the default namespace is  
> declared as
> > > empty:
> > >  >
> > >  > <xf:instance id="text_instance">
> > >  >    <tei:TEI xmlns=""> ...
> > >  >
> > >  > But then, when this instance is submitted, it shows up as:
> > >  >
> > >  > <tei:TEI xmlns=" <http://www.w3.org/1999/xhtml>
> > > <http://www.w3.org/1999/xhtml>http://www.w3.org/1999/xhtml" ...
> > >  >
> > >  > I would like to get rid of this default namespace  
> declaration. I would
> > >  > rather not have to use a non-default namespace for the XHTML  
> elements.
> > >  > Shouldn't the xmlns="" inside the instance override the
> > > xmlns="http..." in
> > >  > the ancestor html element?
> > >  >
> > >  > Does anyone have any ideas? I'm using Firefox  
> (2.0.0.14/0.8.5). I can
> > > ask
> > >  > on the Mozilla XForms list if anyone thinks it is a  
> implementation
> > >  > specific problem.
> > >  >
> > >  > A copy of the form is here:
> > >  > <http://swithun.servebeer.com/namespace.xhtml>
> > > <http://swithun.servebeer.com/namespace.xhtml>http://
> > swithun.servebeer.com/namespace.xhtml
> > >  >
> > >  > Thanks.
> > >  >
> > >  > Swithun.
> > >  >
> > >  >
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Received on Friday, 18 July 2008 19:36:00 GMT

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