[EM] Sequential dropping towards a spanning tree - another immune method related to ranked pairs and river

[Jobst Heitzig]

Hi Markus!

> when the beatpath method is being used then the beatpaths
> from the beatpath winner to the other candidates just form
> an arborescence with the beatpath winner as the root. It
> seems to me that "sequential dropping towards a spanning
> tree" (SDST) just finds this arborescence so that SDST is
> identical to the beatpath method.

That seems to be right indeed -- I should have realized this myself. At
least the winners are identical since (a) whenever the defeat under
consideration is in the current Schwartz set, there is also a beatpath
in the other direction, hence the defeat can be dropped without
destroying the last contained spanning tree, and (b) whenever the defeat
under consideration is not in the current Schwartz set, its removeal
doesn't change the Schwartz set...

So -- was the characterization of the beatpath winner as the root of the
 spanning tree with lexicographically maximal increasing weight sequence
known already -- if so, I apologize :-)

Jobst