This part of BS 5760 provides a description of the principles of the dependability case and provides guidance on its content and application in systems engineering. The dependability case can be used throughout the life cycle, from concept and definition, through design and development; manufacture and installation, to operations and maintenance; mid-life enhancement, and eventual disposal. Whilst this part of BS 5760 is primarily intended for application by the system developers, it will be of value to bodies who might be contracted to manage the dependability case for a project, where deemed necessary. This part of BS 5760 has five main clauses which describe: principles of the dependability case (Clause 5); development of the dependability case (Clause 6); providing the evidence (Clause 7); presenting the evidence (Clause 8); assessing the adequacy of the evidence (Clause 9). The activities required for the achievement of dependability depend on the nature and development state of the system and are likely to vary significantly from one project to another. The guidelines are not to be considered as being prescriptive in nature: they are generic and do not attempt to be exhaustive. Annex A describes the general requirements for the dependability case and dependability case report Annex B provides examples of dependability management risks at different stages of a system’s life cycle. Annex C provides a checklist of points for assessing the adequacy of evidence. The checklist is not to be considered to be prescriptive or exhaustive; it is generic and provides guidance to supplement the generic guidance provided in Clause 8. Annex D describes the dependability risk reduction process shown in Figure 7 using illustrative examples where appropriate. Annex E describes the dependability evidence framework, expanding on the information given in 5.1. Whilst this part of BS 5760 does not specifically address safety cases, the same principles can be applied.