A dog is catching a ball.
The dog is good at catching
A dog could be catching a ball but not be good at catching in general.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_catch(e1) & n_ball(x2) & n_dog(x1))
exists e1 s1 x1 x2.(n_dog(x1) & at(s1,e1) & Actor(e1,x2) & v_catch(e1) & Theme(s1,x1) & a_good(s1))