A small boy washes the dishes.
A boy cleans the pots after dinner.
Not all dishes are pots. The fact that there are dishes doesn't imply that the boy is cleaning up after dinner specifically.
exists e1 s1 x1 x2.(n_dish(x2) & Theme(e1,x2) & Actor(e1,x1) & v_wash(e1) & n_boy(x1) & a_small(s1) & Theme(s1,x1))
exists e1 x1 x2 x3.(n_pot(x2) & after(e1,x3) & n_dinner(x3) & Theme(e1,x2) & Actor(e1,x1) & v_clean(e1) & n_boy(x1))