This boy is going down the slope on skis.
A boy is skiing.
skiing is done down the slope
exists e1 s1 x1 x2 x3.(n_slope(x2) & n_boy(x1) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_go(e1) & on(x2,x3) & n_ski(x3))
exists p1 x1.(exists x2.((x1 = x2) & n_skiing(x2)) & n_boy(x1))