Since a systematic fault may remain even with the quality and safety management processes in place, technical measures bring the resulting risk down to an acceptable level: diversity (different designs, technologies or implementations of redundant items), defensive design, checking of inputs and intermediate results, the techniques and measures of Annex E for the SIL, and for software EN 50128; the measures chosen and the argument that they meet the SIL are recorded in Section 3.6 of the technical safety report.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.