This example demonstrates how to use a SAX parser to build a custom DOM 
inherited from libxml++ nodes. If an application document is sufficiently 
complex, it will have an object hierarchy structure. libxml++ provides a 
generic tree structure with serialization and parsing facilities builtin.
By making classes inherit from libxml++, it is easy to leverage these 
facilities. Classic examples of a custom DOM are the W3C HTML and SVG DOM.
This example barely scratches the surface of a SVG DOM ;-)