Boy and girl running along the beach.
A brother and sister run along the beach
A boy and girl running doesn't mean they are brother and sister.
exists s1 x1 x2 x3 x4.(n_beach(x4) & ne_nam_boy(x1) & a_topic(s1) & subset_of(x2,s1) & along(x2,x4) & n_run(x2) & of(x2,x3) & n_girl(x3) & subset_of(x1,s1))
exists s1 x1 x2 x3 x4.(n_beach(x4) & a_topic(s1) & along(s1,x4) & subset_of(x2,s1) & n_run(x2) & of(x2,x3) & n_sister(x3) & subset_of(x1,s1) & n_brother(x1))