A boy grinds a ledge on his skateboard.
A family eats pizza.
A single boy on a skatebiard is not a family eating pizza.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_grind(e1) & on(x2,x3) & n_skateboard(x3) & of(x3,x1) & n_male(x1) & n_ledge(x2) & n_boy(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_eat(e1) & n_pizza(x2) & n_family(x1))