A man sits on a bridge by a river, playing the accordion.
Someone is by a river
The person could be of any gender, someone is not very specific.
exists e1 e2 x1 x2 x3 x4.(n_accordion(x4) & for(e1,e2) & Theme(e2,x4) & Actor(e2,x1) & v_play(e2) & by(e1,x3) & n_river(x3) & on(e1,x2) & n_bridge(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists p1 x1.(exists x2.(by(x1,x2) & n_river(x2)) & n_person(x1))