We present the `Heisenberg picture' of the reflection algebra by explicitly
constructing the boundary Yangian symmetry of an AdS/CFT superstring which ends
on a boundary with non-trivial degrees of freedom and which preserves the full
bulk Lie symmetry algebra. We also consider the spectrum of bulk and boundary
states and some automorphisms of the underlying algebras.Comment: 31 page, 8 figures. Updated versio
