apg_typeside ty apg_instance G1 : T apg_instance G2 : T apg_morphism h : G1 -> G2 apg_mapping F : S -> T ---------------------------------- apg_morphism (delta F h) : delta F G1 -> delta F G2Delta (model reduct) functor along a schema mapping, applied to an APG morphism that is schema preserving and data natural.