Graph Theoretic Concepts:

A directed graph G =(V,E) consists of a set of vertices V, and a set of edges E, consisting of ordered pairs of vertices. The edge is represented graphically as A®B.
The graph is acyclic if there is no directed cycle A®…®A in G.
A path consists of a sequence of edges such that the endpoints of consecutive edges are the same.
- e.g. A®C¬D®E®F¬B is a path between A and B
A path of the form A® …®B is called a directed path from A to B.