the lextypes function for the parser (a function that
      returns information about the set of token types it produces).
     </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>headline_function</I
></TT
></DT
><DD
><P
>      The name of the headline function for the parser (a function that
      summarizes a set of tokens).
     </P
></DD
></DL
></DIV
><P
>   The function names can be schema-qualified if necessary.  Argument types
   are not given, since the argument list for each type of function is
   predet