The manufacturer identifies which functions are essential performance: during risk analysis it identifies how the clinical functions (other than basic safety) must perform for the intended use to be achieved, or where their performance could affect safety, sets limits somewhere between full function and complete loss for both normal and single fault condition, and evaluates the risk from loss or degradation beyond those limits; where that risk is unacceptable the performance is essential performance and risk control measures bring the risk down to an acceptable level, with the methods used to verify their effectiveness specified, including any assessment of whether verification is needed (the risk control measure, such as a mains-failure alarm with its own power source, may itself become essential performance). Where the standard requires essential performance to be kept after a test, inspection and functional tests are used to confirm showing the manufacturer's limits are held or the equipment moves to a safe state the manufacturer defines.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.