The skier is descending the hill whilst wearing a silver helmet and red backpack.
The skier is not descending the hill
Descending and not descending are not same.
exists e1 e2 s1 x1 x2 x3 x4 x5 x6 x7 x8.(n_whilst(x2) & of(x2,x3) & n_hill(x3) & n_skier(x1) & Theme(e2,x2) & Actor(e2,x1) & v_descend(e2) & Theme(e1,x5) & Actor(e1,x4) & v_wear(e1) & n_backpack(x8) & a_red(s1) & Theme(s1,x8) & n_helmet(x7) & subset_of(x8,x5) & subset_of(x7,x5) & of(x5,x6) & n_silver(x6) & (x2 = x4))
exists x1 x2.(n_hill(x2) & n_skier(x1) & -exists e1.(Theme(e1,x2) & Actor(e1,x1) & v_descend(e1)))