The Representation of a Graph by Set Intersections

Abstract

Geometrically, a graph is a collection of points (or vertices) together with a set of edges (or curves) each of which joins two distinct vertices of the graph, and no two of which have points in common except possibly end points. Two given vertices of the graph may be joined by no edge or one edge, but may not be joined by more than one edge. From an abstract point of view, a graph G is a collection of elements ﹛x 1 , x 2 , …﹜ called points or vertices, together with a second collection of certain pairs (x α , X β ) of distinct points of G . It is helpful to retain the geometric language, and refer to any pair in as an edge (or a curve) of G that joins the points x α and X β .