Male gymnast on the rings.
A man performs gymnastics on the rings.
Being on the rings doesn't mean he performs.  For example he could be practicing.
exists s1 x1 x2.(n_ring(x2) & a_topic(x1) & on(x1,x2) & n_gymnast(x1) & a_male(s1) & Theme(s1,x1))
exists e1 x1 x2 x3.(n_ring(x3) & on(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_gymnastics(x2) & n_man(x1))