This part of IEC61069 : specifies the detailed method of the assessment of functionality of a basic control system (BCS) based on the basic concepts of IEC61069‑1 and methodology of IEC61069‑2 , defines basic categorization of functionality properties, describes the factors that influence functionality and which need to be taken into account when evaluating functionality, and provides guidance in selecting techniques from a set of options (with references) for evaluating the functionality.