Project description: Periodicity as known from Markov chain theory
is defined for directed graphs and its properties are derived by purely
graph theoretic means.
To each strong connected components of a digraph are thus attributed
a period p and and each strong connected component
is decomposed into p
periodicity classes. Paths within a strong connected
component always pass with
each step from one periodicity class to the next returning to the first
class after p steps. An algorithm giving the period of each strong
connected component of a digraph was presented.