A mother and son walk along a dirt path.
There are several people on a hike.
A mother and son are not several people. The mother and may be walking along a dirt path to get from one place to another and are not necessarily on a hike.
exists s1 x1 x2 x3 x4 x5.(a_topic(s1) & along(s1,x4) & n_path(x4) & of(x4,x5) & n_dirt(x5) & Time(s1,x3) & n_walk(x3) & subset_of(x2,s1) & n_son(x2) & subset_of(x1,s1) & n_mother(x1))
exists p1 x1 s1 x2 x3.((x1 = x2) & on(x2,x3) & n_hike(x3) & n_people(x2) & a_several(s1) & Theme(s1,x2))