code: 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('>');
      }
docs: Parse a notation declaration.
  
  <pre>
  [82] NotationDecl ::= '&lt;!NOTATION' S Name S
  (ExternalID | PublicID) S? '&gt;'
  [83] PublicID ::= 'PUBLIC' S PubidLiteral
  </pre>
  
  <P>
  NOTE: the '&lt;!NOTATION' has already been read.