[xml] Newbie question - Getting Node Content from XPath

[Andrew Nelson <andyfaff gmail com>]

Dear List,
sorry, this is a newbie question.  I've already looked through  
examples, and through the library sourcecode, but couldn't find what  
I was looking for.
Suppose I have some XML:

<?xml version="1.0" encoding="ISO-8859-1"?>
<PMML >
  <Header copyright="mine">
     Hello World!
     <Application> foo </Application>
  </Header>
</PMML>

The corresponding XPath nodes are:

/PMML
/PMML/Header
/PMML/Header/Application

This much I can work out (xmlNodePath is your friend)...

However, I don't know how to get the content of each of the nodes.   
For example, given the  full XPath "/PMML/Header" how do I obtain the  
string "Hello World!"?  I've tried using xmlXPathCastNodeToString, on  
the "/PMML/Header" Xpath, but also get foo printed out.
I'm thinking that I may have to use xmlXPathEval, am I heading along  
the right lines?

I'm sorry if this is a simple question.

regards,
Andy