A man sitting in a park is playing a musical instrument.
A man plays the guitar in a park
playing musical instrument doesn't imply playing a guitar
exists e1 e2 s1 x1 x2 x3 x4.(Theme(e2,x4) & Actor(e2,x1) & v_play(e2) & n_instrument(x4) & a_musical(s1) & Theme(s1,x4) & in(e1,x3) & n_park(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_man(x1))
exists e1 x1 x2 x3.(n_guitar(x2) & in(e1,x3) & n_park(x3) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_man(x1))