A shirtless man is riding a motorcycle.
A man is riding a motorcycle to buy a shirt.
The fact that a shirtless man is riding a motorcycle doesn't imply that he is riding to buy a shirt.
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_motorcycle(x2) & n_man(x1) & a_shirtless(s1) & Theme(s1,x1))
exists e1 p1 x1 x2 x3.(Topic(e1,p1) & exists e2 x4.(Theme(e2,x4) & Actor(e2,x1) & v_buy(e2) & n_shirt(x4)) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_motorcycle(x3) & n_man(x2) & n_man(x1))