Scenarios, Stories, Use Cases: Through the Systems Development Life-Cycle

CHAPTER 3

SCENARIOS IN REQUIREMENTS DISCOVERY

Suzanne Robertson

The Atlantic Systems Guild Ltd, London, UK

EXPERIENCED requirements engineers know the truth—most people do not know what their requirements are. When you ask the question, “What are your requirements?” you usually get a response that is in some form of a solution. Or the respondent admits he does not know precisely what he wants but will know it when he sees it—usually in the form of the finished product when it is difficult, if not impossible, to make changes. Why does this happen? Because requirements come from people, and people are influenced and constrained by their own knowledge, experience, imagination, and attitudes. Regardless of whether you are specifying requirements for a banking system, a control system for a pacemaker, a nuclear submarine, a vacuum cleaner or a teddy bear, the requirements must come from people. But each person's requirements will be influenced by his own experience of the world and, someone else might not even consider something that is vital to one person. Given these variations between people, it is not enough to just ask people what they want. We need a variety of different techniques for discovering requirements and we need to choose the technique that best fits each situation.

Scenarios are a technique that is being increasingly used as a requirements discovery tool because a scenario helps people to think past the obvious, to discover the real requirements, and to come up with ...