  In General Relativity, the allowed set of diffeomorphisms or gauge
transformations at asymptotic infinity forms the BMS group, an
infinite-dimensional extension of the Poincar\'e group. We focus on the
structure of the BMS group in two distinct forms of Hamiltonian dynamics - the
instant and front forms. Both similarities and differences in these two forms
are examined while emphasising the role of non-covariant approaches to
symmetries in gravity.
