Use Case Analysis in SDLC Chapter 4

Use Case Analysis

• Use cases are used to illustrate how a system interacts with its environment, showing the activities performed by users and the system's responses.
• Use cases express and clarify user requirements, defining the expected interaction between the user and the system.
• Use cases are used extensively in the analysis phase, often as part of user interviews or JAD (Joint Application Development) sessions.

Use Cases Techniques

• Visual modeling: use case diagrams are used to graphically depict a subset of the use case model to simplify communications.
• Textual document: use case specifications describe the flow of events of the use case.

Elements of a Use Case

• Each use case has a name and number, and brief description.
• Priority may be assigned to indicate the relative significance.
• The actor refers to a person, another system, or a hardware device that interacts with the system to achieve a useful goal.
• The trigger for the use case is the event that causes the use case to begin.

Use Case Styles

• Use case styles can be casual, fully-dressed, or others.
• Fully-dressed use case format is very thorough, detailed, and highly structured.

Creating Use Cases

• Identify events the system must respond to, and develop an Event-Response List.
• Create use case forms for the complex events.
• For each use case, identify the major steps, identify elements with each major step (inputs and outputs), and confirm use case with users through role-playing.
• Revise functional requirements as needed.

Use Case Practical Tips

• Use gradual refinement, concentrating on describing the user's objectives with the system completely and accurately.
• Keep both audiences in mind – users and developers.
• Create use cases only when needed to clarify what the system must do from the user's perspective, not needed for simple events.

Use Cases in Sequence

• Use cases are often performed in sequence, and no single use case should be too large.
• It's important to define initial and ending states.

Preconditions and Postconditions

• Preconditions define what must be complete before beginning the use case.
• Postconditions define what is complete when the use case ends.