Girls playing in a sand playground.
Girls are playing.
Sentence 2 implies the action of playing is happening now and is continuing to happen.
exists x1 x2 x3 x4.(a_topic(x1) & in(x1,x3) & n_playground(x3) & of(x3,x4) & n_sand(x4) & n_playing(x1) & (x1 = x2) & ne_nam_girls(x2))
exists e1 x1.(Actor(e1,x1) & v_play(e1) & n_girl(x1))