docs: private void parseNotationDecl() throws Exception {
          String nname;
          ExternalIdentifiers ids;
  
          requireWhitespace();
          nname = readNmtoken(true);
          // NE08
          if (nname.indexOf(':') >= 0) {
              fatal("Illegal character(':') in notation name ", nname, null);
          }
          requireWhitespace();
  
          // Read the external identifiers.
          ids = readExternalIds(true, false);
  
          // Register the notation.
          setNotation(nname, ids);
  
          skipWhitespace();
          require('>');
      }