this approach seems to allow many-to-one post updates to occur as a single action...

this approach seems to allow many-to-one post updates to occur as a single action.   for one-to-many, we
have it working the old way still. as usual the huge job is the tests.   also I am not yet certain
that post updates can always be a "full mapper" operation, i.e. are never involved in per-state dependencies,
or even if the old approach supports that.