  The exceptional superalgebra $D(2,1;\alpha)$ has been classified as a
candidate conformal supersymmetry algebra in two dimensions. We propose an
alternative interpretation of it as extended BFV-BRST quantisation
superalgebras in 2D ($D(2,1;1) \simeq osp(2,2|2)$). A superfield realization is
presented wherein the standard extended phase space coordinates can be
identified. The physical states are studied via the cohomology of the BRST
operator. It is conjectured that the underlying model giving rise to this
`quantisation' is that of a scalar relativistic particle in 1+1 dimensions, for
which the light cone coordinates $x_R$, $x_L$ transform under worldline
diffeomorphisms as scalar densities of appropriate weight.
