  We introduce S-modules, generalizing the notion of Krein $C^*$-modules, where
a fixed unitary replaces the symmetry of Krein $C^*$-modules. The
representation theory on S-modules is explored and for a given $*$-automorphism
$\alpha$ on a $C^*$-algebra the KSGNS construction for $\alpha$-completely
positive maps is proved. An extention of this theorem for $\tau$-maps is also
achieved, when $\tau$ is an $\alpha$-completely positive map, along with a
decomposition theorem for $\mathfrak K$-families.
