This person is skiing.
this person is on the snow
If the person is on the snow, then the person is on the snow.
exists p1 x1.(n_person(x1) & exists x2.((x1 = x2) & n_skiing(x2)))
exists p1 x1 x2.(n_snow(x2) & n_person(x1) & on(x1,x2))