A crowd is watching a street performer.
Nobody is watching
It cannot be both nobody and a crowd of people.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_watch(e1) & n_performer(x2) & of(x2,x3) & n_street(x3) & n_crowd(x1))
-exists e1 x1.(Actor(e1,x1) & v_watch(e1) & n_person(x1))