// create all built-in types
// we are assumeing that fBuiltInTypes == null
void createBuiltInTypes() {
fBuiltInTypes = new Hashtable();
DatatypeValidator dvTemp;
fBuiltInTypes.put("string", new StringDatatypeValidator());
fBuiltInTypes.put("ID", new IDDatatypeValidator());
dvTemp = new IDREFDatatypeValidator();
fBuiltInTypes.put("IDREF", dvTemp);