A man sings on stage with a guitar.
the man sings a great song
Just because a man sings on stage with a guitar does not necessary that the man sings a great song
exists e1 x1 x2 x3.(on(e1,x2) & with(x2,x3) & n_guitar(x3) & n_stage(x2) & Actor(e1,x1) & v_sing(e1) & n_man(x1))
exists e1 s1 x1 x2.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_song(x2) & a_great(s1) & Theme(s1,x2))