Route planning is a common task. A route plan used to be marked on a paper map, but now it can be easily done on a digital road network using an automotive navigation system or a geographic information system (GIS). A network is a system of linear features that has the appropriate attributes for the flow of objects. A road system is a familiar network; other networks include railways, public transit lines, bicycle paths, utility lines, and streams.

A network data model consists of geometries and attributes. The basic geometric features are edges (links) and junctions (nodes). An edge refers to a line segment defined by two end points. A junction refers to a point, where lines meet or intersect. To be used for route planning, ...