An elderly man and woman observe a wooden contraption with a tube.
A man and woman are observing a wooden contraption operate
The fact that one can observe a contraption doesn't imply that one can operate it.
exists e1 s1 s2 x1 x2 x3 x4 x5.(Theme(e1,x4) & Actor(e1,x1) & v_observe(e1) & with(x4,x5) & n_tube(x5) & n_contraption(x4) & a_wooden(s2) & Theme(s2,x4) & n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1) & a_elderly(s1) & Theme(s1,x1))
exists e1 e2 s1 x1 x2 x3 x4 x5.(Actor(e2,x1) & v_operate(e2) & Theme(e1,x5) & Actor(e1,x4) & v_observe(e1) & n_contraption(x5) & a_wooden(s1) & Theme(s1,x5) & (x1 = x4) & n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1))