Two officers sit on horses in a urban setting.
Two officers patrolling
When officers are patrolling, they are moving around and looking for anything suspicious. In the first sentence, the officers could be sitting on their horses and not moving.
exists e1 s1 x1 x2 x3.(in(e1,x3) & n_setting(x3) & a_urban(s1) & Theme(s1,x3) & on(e1,x2) & n_horse(x2) & Actor(e1,x1) & v_sit(e1) & n_officer(x1) & card_eq_2(x1))
exists e1 x1 x2.(a_topic(x1) & Actor(e1,x2) & v_patrol(e1) & (x1 = x2) & n_officer(x1) & card_eq_2(x1))