a lone rock climber climbing a rock wall
there is a climber on a wall.
If the rock climber is climbing a rock wall, it can also be said that said climber is simply 'on a wall'.
exists e1 s1 x1 x2 x3 x4 x5.(a_topic(x1) & Theme(e1,x4) & Actor(e1,x3) & v_climb(e1) & n_wall(x4) & of(x4,x5) & n_rock(x5) & (x1 = x3) & n_climber(x1) & of(x1,x2) & n_rock(x2) & a_lone(s1) & Theme(s1,x1))
exists p1 x1 x2.(on(p1,x2) & n_wall(x2) & exists x3.((x1 = x3) & n_climber(x3)))