Re: Svar: Re: [xml] XPath problem with namespaces

[Daniel Veillard <veillard redhat com>]

On Tue, Jun 08, 2004 at 09:36:14AM +0200, Fabrice Desré - France Telecom R&D/DTL/TAL wrote:
> Erik F. Andersen wrote:
> > Thanks,
> >
> > that was it. I knew I knew it, there was just too much info at once ;-) 
> > But why can't it simply register all the namespaces from the document 
> > itself in xmlXPathNewContext?
>
>  Because there's no way to predict which prefix will be used in the 
> instance (you can even use a default namespace). So you have to bind the 
> prefix that you will use in the xpath expression, and it can be 
> different from the prefix in the document.

  it's worse than that. Namespace scope is a subtree. You can have 
different prefixes mapped to different namespace in different subtrees.

<top>
  <t xmlns:ns='a'><ns:foo/></t>
  <t xmlns:ns='b'><ns:foo/></t>
</top>

  is perfectly legal as a namespaced document.
If people take the time to read the conformance section of the XPath spec
they will discover that there is no conformance for XPath as-is. The XPath
spec was not designed to be used standalone, but reused by XSLT and XPointer.
As a result the spec does not explain how to apply XPath to a document
or tree, how the evaluation context is initialized was left to be described
by the other specs reusing it.

Daniel
 
-- 
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veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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