Young people sitting on steps.
Old people sit on the porch.
Young people are not old.
exists e1 s1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_step(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_people(x1) & a_young(s1) & Theme(s1,x1))
exists e1 x1 x2 x3.(n_porch(x3) & on(e1,x3) & Actor(e1,x1) & v_sit(e1) & n_people(x1) & (x1 = x2) & ne_nam_old(x2))