Chapter 7. Functional Requirements

in which we look at those requirements that cause the product to do something

The functional requirements specify what the product must do. They describe the actions the product must carry out to satisfy the fundamental reasons for its existence. For example, the functional requirement describes an action the product must take if it is to carry out the work for which it is intended. The intention is to understand the functional requirements and so convey to the developers what the product is required to do for its intended operator.

The product shall predict which road sections will freeze within the selected time parameters.

In Chapter 5, we described how to gather the requirements. In Chapter 6, we described how the requirements analyst uses business use case scenarios to illustrate the functionality for the interested stakeholders, and product use case scenarios to define ideas for the product boundary. When the scenarios have been agreed upon, the requirements analyst writes the functional requirements for the product use cases. This process is illustrated in Figure 7.1.

Figure 7.1.

The functionality of the work is described during the trawling activity. You usually communicate this functionality back to the stakeholders by writing a scenario. You then write functional requirements by referring to the scenario. The end result is a collection of functional requirements that, taken together, describe the product's contribution to the work.

Chapter 5, Requirements, describes how to gather requirements. Chapter 6, Scenarios and Requirements, explores how to use scenarios to describe business use cases and product use cases.