  Shedding a new light in the coarse-graining scenario, in this contribution we
came up with different necessary and sufficient conditions for the existence of
a well-defined coarse-grained state. For doing so, we had to break apart with
the usual quantum channels perspective and assume a more decision-theoretical
posture. Broadly speaking, we reinterpret the coarse-graining problem in the
language of quantum state pooling, and by make an extensive use of the
conditional quantum states toolkit we have been able to derive more tangible
conditions for the emergence of a compatible, effective coarse-grained state.
