A man is sitting in front of a computer monitor holding a keyboard and looking at the camera.
A man is sitting in a chair.
we know that the man is sitting on something but then sentence two tells us it was chair. We didn't know that originally.
exists e1 e3 e2 x1 x2 x3 x4 x5 x6.(n_camera(x6) & for(e1,e3) & at(e3,x6) & Actor(e3,x1) & v_look(e3) & for(e1,e2) & Theme(e2,x5) & Actor(e2,x1) & v_hold(e2) & n_keyboard(x5) & in(e1,x2) & of(x2,x3) & n_monitor(x3) & of(x3,x4) & n_computer(x4) & n_front(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists e1 x1 x2.(in(e1,x2) & n_chair(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))