  Let $(G, \Omega)$ be a Shimura datum of abelian type. It is well known that
the corresponding Shimura variety $\mathrm{Sh}(G, \Omega)$ should be a moduli
space of abelian motives equipped with some additional structures. In this
half-expository note, we give under some simplifying assumptions a moduli
interpretation of $\mathrm{Sh}(G, \Omega)$ over the reflex field purely in
terms of systems of realizations. The main purpose is to introduce some
convenient formalism that can be used to avoid the technicalities about dealing
with various notions of families of motives.
