A quantum field theory on Anti-de-Sitter space can be constructed from a
conformal field theory on its boundary Minkowski space by an inversion of the
holographic mapping. To do this the conformal field theory must satisfy certain
constraints. The structure of operator product expansions is carried over to
AdS space. We show that this method yields a higher spin field theory HS(4)
from the minimal conformal O(N) sigma model in three dimensions. For these
models AdS/CFT correspondence is hereby proved to second order in the coupling
constant.Comment: Latex file, 19 pages; one section added, 3 references added, typos
correcte