Artifact: Use-Case Model

Use-Case Model	The use-case model is a model of the system's intended functions and its environment, and serves as a contract between the customer and the developers. The use-case model is used as an essential input to activities in analysis, design, and test.
UML representation:	Model, stereotyped as ½use-case model╗.
Worker:	System Analyst
Sample Reports:	Use-Case-Model Survey
Examples:	Course Registration System Collegiate Sports Paging System (e-Business)
More information:	Guidelines: Use-Case Model Checkpoints: Use-Case Model Checkpoints: Actors
Purpose Properties Timing Responsibility

Input to Activities: Architectural Analysis Capture a Common Vocabulary Design Test Detail a Use Case Detail the Software Requirements Manage Dependencies Plan Test Prioritize Use Cases Review Requirements Structure the Use-Case Model Use-Case Analysis

Output from Activities: Define Automation Requirements Elicit Stakeholder Requests Find Actors and Use Cases Review Requirements Structure the Use-Case Model

Purpose

The following people use the use-case model:

• The customer approves the use-case model. When you have that approval, you know the system is what the customer wants. You can also use the model to discuss the system with the customer during development.
• Potential users use the use-case model to better understand the system.
• The architect uses the use-case model to identify architecturally significant functionality.
• Designers use the use-case model to get a system overview. When you refine the system, for example, you need documentation on the use-case model to aid that work.
• The manager use the use-case model to plan and follow up the use-case modeling and also the subsequent design.
• People outside the project but within the organization, executives, and steering committees, use the use-case model to get an insight into what has been done.
• People review the use-case model to give appropriate feedback to developers on a regular basis.
• Designers use the use-case model as a basis for their work.
• Testers use the use-case model to plan testing activities (use-case and integration testing) as early as possible.
• Those who will develop the next version of the system use the use-case model to understand how the existing version works.
• Documentation writers use the use cases as a basis for writing the system's user guides.

Properties

Timing

The use-case model primarily sets the functional requirements on the system, and is used as an essential input to analysis and architectural design. It can be used early in the inception phase to outline the scope of the system, as well as during the elaboration phase. The use-case model is refined by more detailed flows of events during the construction phase. The use-case model is continuously kept consistent with the design model.

Because it is a very powerful planning instrument, the use-case model is generally used in all phases of the development cycle.

Responsibility

A system analyst is responsible for the integrity of the use-case model, and ensures that the use-case model as a whole is correct, consistent, and readable. The use-case model is correct when it describes the system's functionality, and only this functionality.

Note that details of use-case packages, use cases, actors, relationships, and diagrams are the responsibilities of the corresponding use-case specifier. For more information, refer to Worker: Use-Case Specifier. The use-case view is the responsibility of an architect. For more information, refer to Worker: Architect.

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