Use Cases !!!

What is a Use Case?

A use case is a description of how a system’s behavior in response to a request from a stakeholder known as an actor. The actor could be a person or an external system that interacts with the system being described.

The actor initiates an action with the system with the purpose of accomplishing a goal. The system responds to the actor’s action in a way that fulfills the interests of all of its stakeholders. A use case summarizes a complete series of related scenarios that may unfold.

Use cases by definition are developed in text format using natural or non-technical language. However, they can also be developed in use case diagram form using UML notation or a combination of both text and diagrams.

Parts of a Use Case

There is no set template for use cases. There are some core sections that are considered the most useful in use cases. You should use as many or as few of these sections as needed to successfully document your system’s requirements. The core sections for use cases are:

– Use case ID
– Use case name
– Version
– Goal
– Summary / Description
– Primary Actor
– Secondary Actor
– Pre-conditions
– Trigger
– Basic course of events
– Exceptions
– Alternative paths
– Post-conditions
– Business rules
– Notes
– Author and date

Why Use Cases?

Use cases can be used to document any type of system. They can be used to document a software system or to document a company’s business processes.

Use cases are useful because they quickly and early clarify how the system will behave when the users interact with it. Use cases are easy for users to understand.

In addition, use cases are helpful for brainstorming conditions under which the system may fail and working out solutions to the problems that fulfill the stakeholders’ interests.

How to Write Use Cases

– Develop a list of usage goals from your stake holders. This is your initial list of use cases.
– Develop a short paragraph describing each use case this will be your summary or description.
– Develop the header section of the use case. The header for each use case should include:
– The Use Case ID Number
– The Use Case Name
– Pre-conditions
– Post-conditions
– Primary Actor
– Secondary Actor
– Trigger

Verify that your use case headers are correct then iterate through them again to add more sections and more details. Further detail sections are:

– Basic Course of Events – steps that the actor and system go through to accomplish a goal
– Exceptions – steps for handling errors and exceptions.
– Alternative Paths – steps for handling variations.

Check your use case for failure points and missing requirements.
As your write your use cases, do it in a way that makes them easy to read. Use natural language. Keep your statements simple and concise.