A characterization of graphs whose vertex set can be partitioned into a total dominating set and an independent dominating set

A set S of vertices in a graph G is a dominating set if every vertex not in S is adjacent to a vertex in S. If, in addition, S is an independent set, then S is an independent dominating set, while if every vertex of the dominating set S is adjacent to a vertex in S, then S is a total dominating set of G. A fundamental problem in domination theory in graphs is to determine which graphs have the property that their vertex set can be partitioned into two types of dominating sets. In particular, we are interested in graphs whose vertex set can be partitioned into a total dominating set and an independent dominating set. In this paper, we solve this problem by providing a constructive characterization of such graphs. We show that all such graphs can be constructed starting from two base graphs and applying a sequence of eleven operations.