T>op</TT>&gt; <I>longvid</I>
	 &lt;<TT>and</TT> <I>econbind</I>&gt; </TD>
    <TD> synonym </TD>
  </TR>
  <TR></TR>
  <TR>
    <TD> <I>spec</I> </TD>
    <TD align="center">::=</TD>
    <TD> ... </TD>
    <TD> </TD>
  </TR>
  <TR>
    <TD></TD> <TD></TD>
    <TD> <TT>exttype</TT> <I>extdesc</I> </TD>
    <TD> extensible datatype </TD>
  </TR>
  <TR>
    <TD></TD> <TD></TD>
    <TD> <TT>constructor</TT> <I>econdesc</I> </TD>
    <TD> generative constructor </TD>
  </TR>
  <TR></TR>
  <TR>
    <TD> <I>extdes