Spidel Tech Solutions, Inc.

Use Case

Here we will consider the notion of the Use Case. A system can be fairly simply described by how it is used. Each separate type of use of a system is called a Use Case. A Use Case Diagram shows users interacting in transactions with the subject system.

For example; Use Cases of a banking system might include deposits and withdrawals among others. A use case definition describes a transaction with the system by one or more actors.

In this case the actors are users but sometimes they are other systems of unknown design. The use case diagram shows lines between actors and bubbles that represent system transactions.

The principal value of a use case is that it forces you to think about who will be interacting with the system and what they will be doing in their role as an actor.

Use case diagrams are often one of the first logical descriptions of a system. Unfortunately they are often neglected as system development proceeds. They can fall out of step with the actual system as deployed if no one is charged with keeping them up to date. This makes acceptance test planning more difficult than necessary. When a customer defines use cases for a proposed system then these later become the major elements of an acceptance test.

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