A kid in blue swim trunks swimming the backstroke.
The kid is taking swimming classes.
A kid doing backstroke does not imply that he is taking swimming classes.
exists e1 s1 x1 x2 x3 x4 x5.(n_backstroke(x5) & a_topic(x1) & in(x1,x2) & Theme(e1,x5) & Actor(e1,x4) & v_swim(e1) & (x2 = x4) & n_trunk(x2) & of(x2,x3) & n_swim(x3) & a_blue(s1) & Theme(s1,x2) & n_kid(x1))
exists e1 x1 x2 x3.(n_kid(x1) & Theme(e1,x2) & Actor(e1,x1) & v_take(e1) & n_class(x2) & of(x2,x3) & n_swimming(x3))