The behaviour you saw is absolutely correct and not a bug at all. To quote the author of libxml2 from a message aptly titled Re: [xml] XPath and default namespaces (bet you're sick of this by now :) ):
You cannot define a default namespace for XPath, period, don't try you can't, the XPath spec does not allow it. This can't work and trying to add it to libxml2 would simply make it non conformant to the spec.
In a nutshell forget about using default namespace within XPath expressions, this will *never* work, you *can't* !
Google [daniel veillard default namespace xpath] if you want more.
As he says, XPath has no notion of a default namespace. //lastName in an XPath expression always matches that element in the null namespace, not the default namespace. According to the spec:
A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null (this is the same way attribute names are expanded).
In //sdnList:lastName, sdnList is not a namespace. Only URIs can be namespaces. The stuff in front of the colon is the prefix, and is merely a stand-in for the URI. <sdnList xmlns="http://tempuri.org/sdnList.xsd"> puts the sdnList element (and all its prefix-less descendants) in the http://tempuri.org/sdnList.xsd namespace. You have to associate this URI with a prefix, then use the prefix in your expression. This is exactly the approach lestrrat posted:
my $xc = XML::LibXML::XPathContext->new( $doc->documentElement() );
$xc->registerNs( foobar => 'http://tempuri.org/sdnList.xsd' );
my $result = $xc->findvalue( '//foobar:lastName' );
I wrote about this a while ago.
Note that the prefix is arbitrary and has nothing to do with what appears in your document. This is as it should be, because the following document means exactly the same as the one you have:
For that matter, even this means the same:
You get the idea.
Makeshifts last the longest.
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