Man is on his bike in the dirt.
A man is riding a mountain bike through the woods.
The terrain is known that the man is riding through but we don't know the setting - the woods - and that the bike is a mountain bike, specifically.
exists p1 x1 x2 x3.(n_dirt(x3) & on(x1,x2) & in(x2,x3) & n_bike(x2) & of(x2,x1) & n_male(x1) & n_man(x1))
exists e1 x1 x2 x3 x4.(n_wood(x4) & through(e1,x4) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & of(x2,x3) & n_mountain(x3) & n_man(x1))