Canonical transformations for hyperkahler structures and hyperhamiltonian dynamics

We discuss generalizations of the well known concept of canonical transformations fo symplectic structures to the case of hyperkahler structures. Different characterizations, which are equivalent in the symplectic case, give rise to non-equivalent notions in the hyperkahler ramework; we will thus distinguish between hyperkahler and canonical transformations. We also discuss the properties of hyperhamiltonian dynamics in this respect