More than one person can hold the same WHS duty and each keeps responsibility for it to the extent they can influence and control the matter (WHS Act s 16). Duty holders must consult, cooperate and coordinate with all others who have a duty on the same matter so far as reasonably practicable (s 46): exchange information, find out who is doing what, and work together so risks are eliminated or minimised. For example a PCBU using labour hire workers and the labour hire company can agree realistic timeframes and make sure workers have the skills and support, to limit high job demands.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.