A couple converses at a table in a bar.
A husband and wife chat at a bar.
Not all couples contain a husband and wife.
exists e1 x1 x2 x3.(at(e1,x2) & in(x2,x3) & n_bar(x3) & n_table(x2) & Actor(e1,x1) & v_converse(e1) & n_couple(x1))
exists s1 x1 x2 x3 x4.(a_topic(s1) & subset_of(x2,s1) & at(x2,x4) & n_bar(x4) & Time(x2,x3) & n_chat(x3) & n_wife(x2) & subset_of(x1,s1) & n_husband(x1))