IEC 60300-3-4:2007

Gives guidance on specifying required dependability characteristics in product and equipment specifications, together with specifications of procedures and criteria for verification.
Includes advice on specifying quantitative and qualitative reliability, maintainability and availability requirements. The main changes from the previous edition are: the concept of systems has been included and the need to specify the dependability of the system and not just the physical equipment has been stressed; the need for verification and validation of the requirement has been included; differentiation has been made between requirements, that can be measured and verified and validated, and goals, which cannot; and  the content on availability, maintainability and maintenance support has been updated and expanded to similar level of detail to reliability.