it is also possible to generalize line graphs to directed graphs. if "g" is a directed graph, its directed line graph or line digraph has one vertex for each edge of "g". two vertices representing directed edges from "u" to "v" and from "w" to "x" in "g" are connected by an edge from "uv" to "wx" in the line digraph when "v" = "w". that is, each edge in the line digraph of "g" represents a length-two directed path in "g". the de bruijn graphs may be formed by repeating this process of forming directed line graphs, starting from a complete directed graph.