A boy in a red coat is playing with a train set.
A boy is riding a train.
Riding and playing are not the same thing. One can not usually be riding a train set as they are small.
exists e1 s1 x1 x2 x3 x4.(with(e1,x3) & n_set(x3) & of(x3,x4) & n_train(x4) & Actor(e1,x1) & v_play(e1) & in(x1,x2) & n_coat(x2) & a_red(s1) & Theme(s1,x2) & n_boy(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_train(x2) & n_boy(x1))