Start with the service
For example, a transit trip needs a vehicle, route, operator, usable street or track, energy and often communications.
Separate direct and indirect dependencies
A pump may directly need electricity while indirectly depending on road access for maintenance.
Look for shared dependencies
Power, telecommunications and road access support many other services.
The map reveals concentration
A single shared dependency can explain why apparently unrelated services fail together.
Scope boundary. This page explains system relationships at a planning level. Real utility, transportation, emergency, structural, electrical, cybersecurity and public-safety decisions require local agencies and qualified professionals.