Any CBS that SOLAS II-1 Regulation 31 requires for local backup control must not depend on the main control system, with its own HMI, self-contained and not relying on other CBSs; where it communicates with remote control or other systems over networks, it forms its own security zone with the safeguards of sections 4.2.1 plus 4.2.2, and otherwise meets this UR (other concepts may be considered case by case).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.