This Technical Report is applicable, where a risk assessment according to ISO 12100 has been conducted for a machine or process plant and where a safety related control function has been selected for implementation as a protective measure against specified hazards. For the given case, this Technical Report describes the basic logical rationale, which is followed to assign a safety integrity requirement to the selected function. This Technical Report is applicable to safety related control functions in all modes of application: continuous mode, high demand mode and low demand mode of application