Re: [Xmlstar-devel] c14n xpath

[Keith B. <KSB...@lb...>]

Well, I'm having trouble finding an introductory reference on xpath that 
includes namespaces (I generally try to avoid starting with the spec but 
it appears I don't have much of a choice here).  But in the meantime...

Shaun McCance wrote:
> The XPath expression isn't part of the XML document, so the namespace
> declarations in the XML document are irrelevant to the XPath expression.
> The prefix-namespace association has to be given to the XPath processor
> for a namespace prefix in an XPath to mean anything.

Seems to me that the same be said about any element or attribute name.

> You might wonder why an XPath processor can't just look at the prefixes
> used in the XML file and use the same ones.

*Exactly* what I'm wondering!

>  Here's an example:
> 
> <foo:foo xmlns:foo="http://example.com/foo">
>   <foo:bar/>
>   <foo:bar xmlns:foo="http://example.com/foobar"/>
> </foo:foo>
> 
> What would the XPath expression //foo:bar select?

I guess I'd expect both foo:bar elements:

<foo:bar/>
<foo:bar xmlns:foo="http://example.com/foobar"/>

Which means that I'm assuming the absence of a namespace specification 
means 'any namespace'.  Bad assumption on my part apparently... :)

So is it possible to provide these prefix-namespace associations in the 
xpath expression itself?  And not pass it in via (what appears to be the 
out-of-band method of) the XPath element?  For example, rather than:

<XPath xmlns:foo="http://example.com/foo">
//foo:bar
</XPath>

something like:

<XPath>
//foo:bar[ns::xmlns:foo="http://example.com/foo">
</XPath>

even though I know that's not the proper syntax.  (I ask because I'm 
working with another xpath implementation (in python) and using xmlstar 
as a reference.)

Thanks so much for your time.
ksb