Topology builds the intersecting node and names the chains. The river is now two chains, with the new node 4 separating the two features. Because direction is important, the starting and ending node identifications are very useful in defining water flow paths. Image 3 shows a more elaborate version of digitized spaghetti and resulting topological structure for a road system. Study the illustration to understand how topology builds nodes and chains to construct recognizable spatial relationships.
Several tables make up a complete topological data structure, as discussed in the next section.
Various tables derived from topological database information . The power behind topology is the set of integrated topology tables containing the data structure information used in feature definition and in determining spatial relationships. The tables are created automatically when topology is applied to the data. As noted, nodes and chains define line and polygon features, and are the important data structure components for topology. Topology traces features by finding nodes, chains, and polygons as needed.