EDGE EXTENSION OF GRAPHS AND DIGRAPHS

In this paper, the concepts of edge (arc) extension of graphs (digraphs) and the edge (arc) extensible class of graphs (digraphs) have been introduced. The classes of regular and eulerian graphs (digraphs) which are not edge (arc) extensible classes have also been introduced. The concept of edge (arc) extensibility number has been introduced as well as the characterization of extensibility number of regular graphs (digraphs). Also the extensibility number of eulerian graphs (digraphs) has been characterized.