code: protected void compareRecognizedXMLSchemaInstanceAttribute(Attr control,
                                                                 Attr test,
                                                                 DifferenceListener listener)
          throws DifferenceFoundException {
          Attr nonNullNode = control != null ? control : test;
          Difference d = 
              XMLConstants.W3C_XML_SCHEMA_INSTANCE_SCHEMA_LOCATION_ATTR
              .equals(nonNullNode.getLocalName())
              ? SCHEMA_LOCATION : NO_NAMESPACE_SCHEMA_LOCATION;
  
          if (control != null) {
              controlTracker.visited(control);
          }
          if (test != null) {
              testTracker.visited(test);
          }
          
          compare(control != null ? control.getValue() : ATTRIBUTE_ABSENT,
                  test != null ? test.getValue() : ATTRIBUTE_ABSENT,
                  control, test, listener, d);
      }
docs: Compare two attributes
  @param control
  @param test
  @param listener
  @throws DifferenceFoundException