  We suggest a combinatorial classification of metric filtrations in measure
spaces; a complete invariant of such a filtration is its combinatorial scheme,
a measure on the space of hierarchies of the group~$\mathbb Z$. In turn, the
notion of combinatorial scheme is a source of new metric invariants of
automorphisms approximated via basic filtrations. We construct a universal
graph endowed with an adic structure such that every automorphism can be
realized in its path space.
