In the skate park, a guy is skateboarding and another is biking.
a skater and a bike rider compete against each other
Just because two people are at the skate park does not mean that they compete against each other.
exists e2 e1 x1 x2 x3 x4 x5 x6.(n_park(x5) & of(x5,x6) & n_skate(x6) & n_park(x2) & of(x2,x3) & n_skate(x3) & in(e2,x5) & Actor(e2,x4) & v_bike(e2) & n_thing(x4) & in(e1,x2) & Actor(e1,x1) & v_skateboard(e1) & n_guy(x1))
exists e1 x1 x2 x3 x4.(all x5.(n_other(x5) -> against(e1,x5)) & Actor(e1,x1) & v_compete(e1) & subset_of(x3,x1) & n_rider(x3) & of(x3,x4) & n_bike(x4) & subset_of(x2,x1) & n_skater(x2))