code: private boolean hasChanges(final Map<URI, URI> changeTable) {
          if (changeTable.isEmpty()) {
              return false;
          }
          for (Map.Entry<URI, URI> e : changeTable.entrySet()) {
              if (!e.getKey().equals(e.getValue())) {
                  return true;
              }
          }
          return false;
      }
docs: Test whether there are changes that require topic rewriting.