Saeid Hanifehnezhad - Department of Mathematics, Shahed University, Tehran, Iran.
Ardeshir Dolati - Department of Computer Science, Shahed University, Tehran, Iran.

Submodularity is an important  property of set functions with deep theoretical results  and various  applications. Submodular systems appear in many applicable area, for example machine learning, economics, computer vision, social science, game theory and combinatorial optimization.  Nowadays submodular functions optimization has been attracted by many researchers.  Pendant pairs of a symmetric submodular system  play  essential role  in finding a minimizer of this system.  In this paper,  we investigate some relations between pendant  pairs of  a  submodular  system and pendant pairs of its contractions. For a symmetric submodular system $left(V,fright)$ we construct a suitable sequence of $left|Vright|-1$ pendant pairs of its contractions. By using this sequence, we present some properties of the system and its contractions. Finally, we prove some results about the minimizers of a posimodular function.

Submodular system, Submodular optimization, Maximum adjacency ordering, Posimodular functions, Pendant pairs, st-cut