  The $SU(3)$ meson exchange approach to interactions within the baryon octet
and nuclear density functional theory are used to derive an \emph{ab initio}
description of hypernuclear interactions. The density dependence of
interactions is recast into a DFT with density dependent interaction vertices.
The field-theoretical structure is retained by expressing the vertices as
functionals of the matter field operators. Applications to infinite hypermatter
and neutron star matter are discussed. A new approach is presented allowing to
determine in-medium coupling constants out of the $NN$-vertex functionals,
obtained e.g. by DBHF theory, for the full baryon octet by exploiting $SU(3)$
relations.
