  In this paper we give a review of the method of imsets introduced by Studeny
(2005) from a geometric point of view. Elementary imsets span a polyhedral cone
and its dual cone is the cone of supermodular functions. We review basic facts
on the structure of these cones. Then we derive some new results on the
following topics: i) extreme rays of the cone of standardized supermodular
functions, ii) faces of the cones, iii) small relations among elementary
imsets, and iv) some computational results on Markov basis for the toric ideal
defined by elementary imsets.
