Children stand and wait for the train.
Kids are waiting for the train while their parents are purchasing tickets.
The kids may already have tickets, the parents aren't there and they may not be buying tickets if they are.
exists e1 s1 x1 x2 x3 x4.(n_train(x4) & a_topic(s1) & subset_of(x3,s1) & for(x3,x4) & n_wait(x3) & subset_of(x1,s1) & Actor(e1,x2) & v_stand(e1) & (x1 = x2) & n_child(x1))
exists e1 p1 x1 x2 x3.(n_parent(x3) & of(x3,x2) & n_thing(x2) & n_train(x2) & exists e2 x4.(Theme(e2,x4) & Actor(e2,x3) & v_purchase(e2) & n_ticket(x4)) & while(e1,p1) & for(e1,x2) & Actor(e1,x1) & v_wait(e1) & n_kid(x1))