It is important to consider the whole lifecycle of the product, not just its main use. This might include manufacture, distribution, support and disposal.

In addition, there may be other functions relevant to the use of the product, from the point of purchase to the point of disposal.

When trying to articulate the detailed requirements for each function, it may be helpful to consider the following questions

• How well? e.g. quality
• How often? e.g. rate
• How fast? e.g. cycle time
• How safe? e.g. safety targets
• How much? e.g. costs
• How soon? e.g. schedule
• How recorded? e.g. documentation