A crowd watches a performance.
The crowd is riding a roller coaster.
It would be difficult and unusual to watch a performance while riding a roller coaster.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_watch(e1) & n_performance(x2) & n_crowd(x1))
exists e1 x1 x2 x3.(n_crowd(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_coaster(x2) & of(x2,x3) & n_roller(x3))