A simplified data table is shown, demonstrating how topology builds the chain and node information used to recognize the spatial relationships. Image 2 applies topology to Afghanistan and Pakistan borders. The table is almost identical to Image 1 and there is very little difference between the conceptual model and the real world application. Features are first digitized into the GIS as they are outlined from the map, and the resulting lines are without connection or intelligence. There is no informational content to the lines except location.
Topology establishes the needed information.
Topology builds the spatial information by recognizing nodes at the ends of each digitized line and creating new nodes at intersections where lines cross, thereby making true topological chains. They are not functionally connected at this time but are merely two lines standing alone, with no recognized spatial relationship. Image 2shows a river and its smaller tributary. Topology builds the intersecting node and names the chains. The river is now two chains, with the new node 4 separating the two features.