The man is riding his bike along a trail.
A man riding a mountain bike.
The man riding his bike, is not imply to be a mountain bike.
exists e1 x1 x2 x3.(n_bike(x2) & of(x2,x1) & n_male(x1) & n_man(x1) & along(e1,x3) & n_trail(x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1))
exists e1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_bike(x3) & of(x3,x4) & n_mountain(x4) & (x1 = x2) & n_man(x1))