A man is midair on a bike over some stairs.
A girl walks her bike down the street.
The subject is either a man or a girl. Also, the setting is different: the bike is either in midair over stairs or calmly being walked down the street.
exists p1 x1.(exists x2 x3 x4.((x1 = x2) & on(x2,x3) & over(x3,x4) & n_stair(x4) & n_bike(x3) & n_midair(x2)) & n_man(x1))
exists e1 x1 x2 x3.(n_street(x3) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & down(x2,x3) & n_bike(x2) & of(x2,x1) & n_female(x1) & n_girl(x1))