A man is hanging upside down.
a man is hanging upside down.
A man does not necessarily imply a man (though in fact it does).
exists e1 p1 x1.(exists s1.(r_upside(s1) & Theme(s1,x1) & a_down(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_hang(e1) & n_man(x1))
exists e1 p1 x1.(exists s1.(r_upside(s1) & Theme(s1,x1) & a_down(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_hang(e1) & n_man(x1))