Two people hiking on a trail.
Two people are walking.
Walking is not hiking.
exists e1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_trail(x3) & Actor(e1,x2) & v_hike(e1) & (x1 = x2) & n_people(x1) & card_eq_2(x1))
exists e1 x1.(Actor(e1,x1) & v_walk(e1) & n_people(x1) & card_eq_2(x1))