Directed Graphs

Def Directed Graph A directed graph, also called a digraph, is a graph in which the edges have a direction. A directed graph is an ordered pair where is a set whose elements are called vertices or nodes. is a set of ordered pairs of vertices, called arcs or directed edges. A digraph thus consists of two functions, source and target .

Def Path A path is a finite sequence of edges in a graph such that for all .

Def Directed Graph Homomorphism Directed graph homomorphism is a mapping of edges to edges and vertices to vertices that preserves sources and targets.