Domination graph

Domination graph --- граф доминирования. Let [math]\displaystyle{ D }[/math] be a digraph with a vertex set [math]\displaystyle{ V(D) }[/math] and an arc set [math]\displaystyle{ A(D) }[/math]. If [math]\displaystyle{ (x,y) \in A(D) }[/math], then [math]\displaystyle{ x }[/math] dominates [math]\displaystyle{ y }[/math]. A vertex is also considered to dominate itself. The domination graph of [math]\displaystyle{ D }[/math], [math]\displaystyle{ dom(D) }[/math], is the graph, where [math]\displaystyle{ V(dom(D)) = V(D) }[/math] and [math]\displaystyle{ \{x,y\} \in E(dom(D)) }[/math], whenever [math]\displaystyle{ x }[/math] and [math]\displaystyle{ y }[/math] dominate all other vertices in [math]\displaystyle{ D }[/math].