This explicitly defines spatial relationships between connecting or adjacent features in geographic data; the arrangement that defines how point, line, and polygon features share coincident geometry. In geography, topology generally refers to the location of nodes and their connectivity to other nodes to form networks. The London Tube map is a topological map, for the connections are important, and not the precise location of nodes and routes. In a geographic information system, topology is a set of rules that define the relationship between points, lines, and polygons. ESRI enables topology generation within its geodatabase feature classes.