  While ostensibly coined in 1989 by Xiao-Gang Wen, the term "topological
order" has been in use since 1972 to describe the behavior of the classical xy
model. It has been noted that the xy model does not have Wen's topological
order since it is also subject a non-topological U(1) gauge action. We show in
a sense this is the only obstruction. That is, if gauge invariance is enforced
energetically then the $xy$ model becomes purely topologically ordered. In
fact, we show that the quantum $xy$ topological order is an infinite lattice
limit of Kitaev's quantum double model applied to the group G=Z.
