code: protected void compareAttribute(Attr control, Attr test,
                                      DifferenceListener listener) throws DifferenceFoundException {
          controlTracker.visited(control);
          testTracker.visited(test);
          
          compare(control.getPrefix(), test.getPrefix(), control, test, 
                  listener, NAMESPACE_PREFIX);
                  
          compare(control.getValue(), test.getValue(), control, test,
                  listener, ATTR_VALUE);
  
          compare(control.getSpecified() ? Boolean.TRUE : Boolean.FALSE,
                  test.getSpecified() ? Boolean.TRUE : Boolean.FALSE,
                  control, test, listener, ATTR_VALUE_EXPLICITLY_SPECIFIED);
      }
docs: Compare two attributes
  @param control
  @param test
  @param listener
  @throws DifferenceFoundException