A skier going goes down the mountain.
The skier climbs up the mountain.
A skier cannot both go down and up the mountain at the same time.
exists e2 e1 x1 x2 x3.(n_mountain(x3) & down(e2,x3) & Actor(e2,x1) & v_go(e2) & Actor(e1,x2) & v_go(e1) & (x1 = x2) & n_skier(x1))
exists e1 s1 x1 x2.(n_mountain(x2) & n_skier(x1) & a_up(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_climb(e1))