This class is the default element handler from which
user-defined element handlers can inherit. It is provided for convenience:
use is optional. The individual methods of the default element handler
do nothing with the content; in a subclass it is therefore only necessary to implement
those methods that need to do something specific.
The startElement() method calls applyTemplates(), so child elements will
always be processed.
Define action to be taken before an element of this element type.
Default implementation does nothing, other than causing subordinate elements
to be processed in the same mode as the caller