People and camels at a beach.
The people are riding the camels.
Being with camels at a beach doesn't imply riding the camels.
exists s1 x1 x2 x3.(a_topic(s1) & subset_of(x2,s1) & at(x2,x3) & n_beach(x3) & n_camel(x2) & subset_of(x1,s1) & n_people(x1))
exists e1 x1 x2.(n_camel(x2) & n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1))