EMPTY::  .

NOTION:: ALPHA NOTETY; <NOTION>.
NOTETY:: NOTION; EMPTY.
ALPHA:: a;b;c;d;e;f;g;h;i;j;k;l;m;n;o;p;q;r;s;t;u;v;w;x;y;z.

program:          abc.

abc:              pack of <seq of <star symbol>>.

pack of <NOTION>: lpar symbol, NOTION, rpar symbol.

seq of <NOTION>:  NOTION, seq of <NOTION>; EMPTY.

opt <NOTION>:     NOTION; EMPTY.    { not conn. }

lpar symbol:   '('.
rpar symbol:   ')'.
star symbol:   '*'.