We characterize normalization by evaluation as the composition of a
self-interpreter with a self-reducer using a special representation scheme, in
the sense of Mogensen (1992). We do so by deriving in a systematic way an
untyped normalization by evaluation algorithm from a standard interpreter for
the ?-calculus. The derived algorithm is not novel and indeed other published
algorithms may be obtained in the same manner through appropriate adaptations
to the representation scheme
