They are playing ice-hockey.
Canadians enjoy their national sport.
Just because they are playing ice-hockey, you can't assume they are Canadians or that ice-hockey is their national sport.  Someone playing ice-hockey could Americans.
exists e1 x1 x2.(n_thing(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_ice-hockey(x2))
exists e1 s1 x1 x2.(n_sport(x2) & a_national(s1) & Theme(s1,x2) & of(x2,x1) & n_thing(x1) & ne_nam_canadians(x1) & Theme(e1,x2) & Actor(e1,x1) & v_enjoy(e1))