Nodes are associated with specific geographic locations in many important networks, for example the following:
- Electrical grids
- Road networks
- Airports linked by direct flights
- Telecommunication lines
The edges in these networks are physical objects and have physical properties that can influence the behavior of the system represented by the network. One weight measure isn't always enough. For example, when an edge represents a fiber optic telecommunications cable, it is important to consider both the physical length of the cable and the bandwidth (capacity) of the cable. The former influences how long signals take to travel along the cable, while the latter influences how much data it can handle (and both of these influences cost!). Not to mention that a telecommunication cable is only useful if it connects two physical locations with people who want to...
