Represents an extension namespace for XPath that handles java classes. It is recommended that the class URI be of the form:

   xalan://fully.qualified.class.name
 

However, we do not enforce this. If the class name contains a a /, we only use the part to the right of the rightmost slash. In addition, we ignore any "class:" prefix. Provides functions to test a function's existence and call a function. Also provides functions to test an element's existence and call an element.