AssertionBuilder is the interface which must implement by any
CustomAssertionBuilder. It defines a single method which takes an element
definitionand an AssertionFactory instance and creates an Assertion. The
AssertionBuilder must use one of the types for which there is a
Converter registered. By default, that would be either an Element,
and XMLStreamReader, or OMElement (if Axiom is available).
Custom AssertionBuilder authors can use the AssertionFactory
specified to build Assertions for any unknown elements inside the given
element. They are given the opportunity to control the behavior of
Assertion operations based on the corresponding domain policy assertion of
the given element and the level of its processing.