By a counter-example, we show that the set of the three spin components Sx, Sy, Sz of spin-1 systems is not informationally complete.

Based on three different types of affine mappings between the corresponding convex sets of states, three different kinds of relations between quantum mechanics and classical physics are reviewed.

It is shown that, to a certain extent, the statistical framework of Hilbert-space quantum mechanics can be reformulated in classical terms.