Naturally submodular digraphs and forbidden digraph configurations ?
In this paper, we present several characterizations of the classes of naturally submodular digraphs and naturally submodular bi-directed graphs. For each class, one characterization is given in terms of forbidden digraph configurations and the other in terms of graph decomposition. For the class of bi-directed graphs, an additional characterization in terms of the fixed-order property is also derived.
primary: 05c75 secondary: 05c38