(VAR x y z )
(RULES 
        f(g(x),y,z) -> f(x,y,g(z))
        f(x,y,g(z)) ->= f(x,g(y),z)
        f(x,a,z) ->= f(x,g(a),z)
        f(x,y,z) ->= f(x,y,g(z))
)