Which abstraction supports walking-route planning?

You want to find the shortest walking route from home to a sports center. Shortest means the smallest total distance, measured in meters. Each street section joins two named places, such as intersections, home, or the sports center. Some sections are closed to pedestrians. Every open section can be walked in either direction.

Which representation keeps enough information to find and compare permitted routes? Each option lists all the information you would have available.

  1. The named places; a connection between every pair of places; the straight-line distance between each pair.
  2. The named places; the pairs joined by open pedestrian street sections; the estimated walking time of each section.
  3. The named places; the pairs joined by any street section, with no record of closures; the length of each section.
  4. The named places; the pairs joined by open pedestrian street sections; the length in meters of each section.