Let $C$ be a semidualizing module. We first investigate the properties of finitely generated $G_C$-projective modules. Then, relative to $C$, we introduce and study the rings over which every submodule of a projective (flat) module is $G_C$-projective (flat), which we call $C$-Gorenstein (semi)hereditary rings. It is proved that every $C$-Gorenstein hereditary ring is both cohe...
