This part of ISO/IEC 15504 provides guidance on meeting the minimum set of requirements for performing an assessment contained in ISO/IEC 15504-2. It provides an overview of process assessment and interprets the requirements through the provision of guidance on: a) performing an assessment; b) the measurement framework for process capability; c) process reference models and process assessment models; d) selecting and using assessment tools; e) competency of assessors; f) verification of conformity. This document uses the following schema: the text inside a box is quoted from the normative ISO/IEC 15504-2 and the text following a box is guidance about the normative text. If the quoted text includes a clause reference, it is understood that ISO/IEC 15504-2 should be referred to.