A young boy is rock climbing while suspended in a harness.
A boy is skiing down a mountain.
One cannot be skiing and rock climbing at the same time.
exists p1 s1 x1.(exists s2 x2 x3 x4 x5.((x1 = x2) & in(s2,x5) & n_harness(x5) & Theme(s2,x4) & a_suspend(s2) & (x2 = x4) & n_climb(x2) & of(x2,x3) & n_rock(x3)) & n_boy(x1) & a_young(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_ski(e1) & n_mountain(x2) & n_boy(x1))