A man is walking across a city street with his son.
The man is walking with his daughter.
It can only be either a son or a daughter.
exists e1 x1 x2 x3 x4.(with(e1,x4) & n_son(x4) & of(x4,x1) & n_male(x1) & across(e1,x2) & n_street(x2) & of(x2,x3) & n_city(x3) & Actor(e1,x1) & v_walk(e1) & n_man(x1))
exists e1 x1 x2.(n_daughter(x2) & of(x2,x1) & n_male(x1) & n_man(x1) & with(e1,x2) & Actor(e1,x1) & v_walk(e1))