public Parser dtColPos() {
        if (dtColPosParser == null) {
           FutureParser future = scoped("dtColPos");
           dtColPosParser = future;
           future.setParser(
               sequence(
                   choice(
                       token("COL"),
                       token("COLUMN"),
                       token("POSITION"),
                       token("POS")
                   ),
                   optional(
                       token("NUMBER")
                   ),
                   optional(
                       token("IS")
                   ),
                   optional(
                       choice(
                           token("PLUS"),
                           token("+"),
                           token("-")
                       )
                   ),
                   choice(
                       identifier(),
                       literal()
                   )
               )
           );
        }

        return dtColPosParser;
    }