Use Case analysis is quite accessible as there are only three aspects to a Use Case analysis:

• The Use Case Scenario
• The Use Case
• The Use Case Diagram

The Use Case Scenario is usually one of the first steps to emerge from analysis planning and can be a result of a brainstorming between those involved in the project. The aim of the scenario should be to ask a question of the existing system with the aim of understanding behaviour, interaction, and problems.

A simplified example scenario might be “A patient is unwell and wants to see the Doctor, so they make an appointment then visit the Doctor for a diagnosis which may or may not result in a Prescription being given. The Doctor will update the patient records.”

The above scenario can already be separated into at least two primary tasks: “making an appointment” and “visiting the Doctor”. Each of these tasks can then become the subject of its own Use Case which, through discussion and interview with individuals involved in the task, can identify and break down the individual steps involved. If necessary, the task can be further broken down into additional Use Case analysis as required.

When progressing to the Use Case stage it is important to define the people involved in the task – for our purposes let’s call these people “Actors” and in our scenario they are likely to be Patient, Doctor, and Receptionist. From the identification of the actors and the scenario we can begin to form a picture of how a task may be accomplished and the first run through of these tasks should highlight how the task is achieved when everything is in order, or a “Sunny Day” as they are often called. For example let’s assume the Patient visits the surgery in person, and that the Receptionist manages to fit the Patient into the Doctors schedule, that the examination runs smoothly and a resulting prescription is offered.

The important thing to remember during the Use Case phase is not to get too bogged down in the details (they can be refined later) – the Use Case is looking for an overview of the task. As Ivar Jacobson says “use cases can be exceptionally lightweight (a brief description only), to lightweight (just an outline of the flows), to comprehensive (full descriptions of all behavior), and every variation in between” (Source: Use-cases – why successful and popular?).