Any mapped feature that represents the delineation between two and only two areas. Topologically, a boundary (also called an edge) is an undirected chain (arc, line segment, 1-cell) between nodes (0-cells). Boundaries are often restructured into closed areas using some form of chaining routine. In topological chaining procedures, boundaries must be chained twice, once in the direction of digitizing and once opposite the direction of digitizing. These two directions are often called left and right and are maintained as attributes to the border for use in a variety of spatial analytical functions (e.g., boundary dissolving, polygon-to-grid conversion, polygon overlay, and chloroplast mapping).