Karate students practicing on a mat.
The students are playing soccer.
Karate students practicing  on a mat can not be playing soccer at the same time.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x4) & n_mat(x4) & Actor(e1,x3) & v_practice(e1) & (x1 = x3) & n_student(x1) & (x1 = x2) & ne_nam_karate(x2))
exists e1 x1 x2.(n_student(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_soccer(x2))