  In this paper we fill a necessary gap in order to realize the explicit
comparison between the Kaluza Klein spectra of supergravity compactified on
AdS_4 x X^7 and superconformal field theories living on the world volume of
M2-branes. On the algebraic side we consider the superalgebra Osp(N|4) and we
study the double interpretation of its irreducible representations either as
supermultiplets of particle states in the bulk or as conformal superfields on
the boundary. On the lagrangian field theory side we construct, using rheonomy
rather than superfield techniques, the generic form of an N=2, d=3 gauge
theory. Indeed the superconformal multiplets are supposed to be composite
operators in a suitable gauge theory.
