A man and a woman talk while standing next to a tree.
A cat and a dog chasing each other.
The man and woman can't be a cat and a dog.
(x)
exists s1 x1.(a_topic(s1) & all x2.(n_other(x2) -> exists x3 x4.(subset_of(x3,s1) & for(x3,x2) & n_chasing(x3) & of(x3,x4) & n_dog(x4))) & subset_of(x1,s1) & n_cat(x1))