A beagle is playing with a tennis ball.
A beagle plays fetch with a tennis ball.
The beagle plays fetch could mean that, in general, the beagle plays fetch. i.e. it is an activity the dog likes to do. It does not mean the beagle is currently playing fetch.
exists e1 x1 x2 x3.(with(e1,x2) & n_ball(x2) & of(x2,x3) & n_tennis(x3) & Actor(e1,x1) & v_play(e1) & n_beagle(x1))
exists e1 x1 x2 x3 x4.(with(e1,x3) & n_ball(x3) & of(x3,x4) & n_tennis(x4) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_fetch(x2) & n_beagle(x1))