Several people are walking down a trail.
The people on the trail are playing catch together.
People can't  be walking down a trail and playing at the same time
exists e1 s1 s2 x1 x2.(a_down(s2) & Manner(e1,s2) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_trail(x2) & n_people(x1) & a_several(s1) & Theme(s1,x1))
exists e1 s1 x1 x2 x3.(n_trail(x2) & n_people(x1) & a_together(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x1) & v_play(e1) & n_catch(x3) & on(x1,x2))