Item Definition (ISO 26262-3:2018 Clause 5)

One of the first tasks ahead of you when starting your Concept Phase (See Part 3 – Concept Phase of ISO 26262) is the generation of an Item Definition. The Item Definition will serve to provide insight into the “Item” that requires a Functional Safety Life Cycle, to those that will be responsible for it, by describing the “Item” and its relationship to the world in which it will exist.

There are two objectives for an item definition, the first objective is to define and describe the item, its dependencies on, and interaction with, the environment and other items. The second objective is to support an adequate understanding of the item so that the activities in subsequent phases can be performed.

It has been found to be one of the most important documents created during the safety life-cycle. A good item definition is vital to the success of all steps that follow in the safety life-cycle.

The importance of the item definition cannot be overstated.  Unfortunately, this is usually only understood with experience of having tried to progress with a poorly defined item.

ISO 26262:2011 2-5.5 only specifies what the item definition needs to contain but does not detail how to produce it.

The work product offered here contains best practice guidance for producing an Item Definition to comply with ISO 26262:2011 2-5.5.  It includes advice on when to write it, how to manage stakeholders expectations, and how to minimise change.