  I review the relationship between AdS/CFT (anti-de Sitter / conformal field
theory) dualities and the general theory of unitary lowest weight (ULWR)
(positive energy) representations of non-compact space-time groups and
supergroups. The ULWR's have the remarkable property that they can be
constructed by tensoring some fundamental ULWR's (singletons or doubletons).
Furthermore, one can go from the manifestly unitary compact basis of the ULWR's
of the conformal group (Wigner picture) to the manifestly covariant coherent
state basis (Dirac picture) labelled by the space-time coordinates. Hence every
irreducible ULWR corresponds to a covariant field with a definite conformal
dimension. These results extend to higher dimensional generalized spacetimes
(superspaces) defined by Jordan (super) algebras and Jordan (super) triple
systems. In particular, they extend to the ULWR's of the M-theory symmetry
superalgebra OSp(1/32,R).
