An individual is skiing or snowboarding
Someone skiing down a slope.
Just because someone is skiing doesn't mean it's down a slope.
(exists e1 x1.(Actor(e1,x1) & v_ski(e1) & n_individual(x1)) | exists e2 x2.(Actor(e2,x2) & v_snowboard(e2) & n_individual(x2)))
exists x1 x2.(a_topic(x1) & down(x1,x2) & n_slope(x2) & n_skiing(x1))