A snowboarder takes a ramp made of snow while others watch.
A skier goes down a hill alone.
Snowboarding and skiing are different types activities in the snow. Others refer to multiple people and not just alone.
exists e2 e1 p1 x1 x2 x3 x4.(Theme(e2,x2) & Actor(e2,x1) & v_take(e2) & exists e3 x5.(Actor(e3,x5) & v_watch(e3) & -(x5 = x1) & n_person(x5)) & n_person(x1) & while(e1,p1) & of(e1,x4) & n_snow(x4) & Theme(e1,x3) & v_make(e1) & (x2 = x3) & n_ramp(x2) & n_snowboarder(x1))
exists e1 s1 x1 x2.(a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_go(e1) & r_alone(x2) & n_hill(x2) & n_skier(x1))