a swimmer doing a backstroke
A swimmer swims.
A backstroke implies swims.
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_do(e1) & n_backstroke(x3) & (x1 = x2) & n_swimmer(x1))
exists x1 x2.(a_topic(x1) & n_swim(x1) & of(x1,x2) & n_swimmer(x2))