A man and a boy are standing next to a train.
A man and boy are standing by a train.
A man and a boy standing next to a train do just that.
exists e1 x1 x2 x3 x4.(to(e1,x4) & n_train(x4) & r_next(e1) & Actor(e1,x1) & v_stand(e1) & subset_of(x3,x1) & n_boy(x3) & subset_of(x2,x1) & n_man(x2))
exists e1 x1 x2 x3 x4.(by(e1,x4) & n_train(x4) & Actor(e1,x1) & v_stand(e1) & n_boy(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1))