Committed several big patches over the last week or so, the end result of which is that the XPath engine, DOM and SAX are (as far as I can tell) fully parameterised on string type. There are a couple of things left to clear up, but it's essentially done.

Up to now, the XPath engine had been confined to std::strings, so this is good news I think. By way of a test, I've been building and testing using this custom string class
  class silly_string
  {
  public:
    silly_string();
    silly_string(const silly_string& rhs);
    ~silly_string();
  
    bool operator==(const silly_string& rhs) const;
    silly_string& operator=(const silly_string& rhs);
  
  private:
    ...
  }; // class silly_string
Default and copy constructor, equality and assignment operators - I think those are reasonable things to expect from a string class :) Everything else is dealt with by the string adaptor class, which I've also reworked a little. I'll describe that in more detail later.