This text book is related to mathematical modeling of some aspects of digraphs with impetus of isomorphism, decyclization and pebbling.There is a rapid growth in graph theory over last two decades among applied mathematicians and engineers. There was one book on the graph theory entitled as Konig's Theorie der Endlichen und Unendlichen Graphen in 1957. Now, there are several textbooks, various seminar and conferences. Chapter I presents the essential preliminaries related to graph, digraph, graph isomorphism, graph decyclization, graph pebbling, graph rubbling, and their applications. Also, it covers the objectives of our research. Chapter II consists of, review of the literature regarding graph theory, graph isomorphism, decyclization of a digraph, graph pebbling, and graph rubbling. Chapter III presents materials and methods for graph isomorphism, graph decyclization, graph pebbling, and graph rubbling. Chapter IV is devoted to results and discussions for graph isomorphism, graph decyclization, graph pebbling, and graph rubbling. Chapter V discusses conclusions regarding findings of results of graph isomorphism, graph decyclization, graph pebbling, and graph rubbling.