code: private ComparisonState
          compareDocTypes(DocumentType control,
                          XPathContext controlContext,
                          DocumentType test,
                          XPathContext testContext) {
          return compare(new Comparison(ComparisonType.DOCTYPE_NAME,
                                        control, getXPath(controlContext),
                                        control.getName(), getParentXPath(controlContext),
                                        test, getXPath(testContext),
                                        test.getName(), getParentXPath(testContext)))
              .andThen(new Comparison(ComparisonType.DOCTYPE_PUBLIC_ID,
                                      control, getXPath(controlContext),
                                      control.getPublicId(), getParentXPath(controlContext),
                                      test, getXPath(testContext),
                                      test.getPublicId(), getParentXPath(testContext)))
              .andThen(new Comparison(ComparisonType.DOCTYPE_SYSTEM_ID,
                                      control, null, control.getSystemId(), null,
                                      test, null, test.getSystemId(), null));
      }
docs: Compares properties of the doctype declaration.