Uses of Use Cases

The term “use case” is a chameleon in the tech world—its meaning shifts depending on context. While it always centers on scenarios or interactions, its purpose and structure vary dramatically across software design, system modeling, and project planning. This article breaks down the three primary interpretations of “use cases” and identifies their common threads.

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1. Use Cases in UML (Unified Modeling Language)

Purpose:
To model system behavior by documenting how users (actors) interact with a system to achieve goals.

Key Traits:

• Visual & Descriptive: Represented as diagrams (UML use case diagrams) and/or text descriptions.
• Actor-Centric: Focuses on interactions between external actors (users, systems) and the system.
• Scenario-Driven: Captures primary flows, alternate paths, and error handling.

Example:

• Use Case: Place Order
• Actors: Customer, Payment Gateway
• Flow:
  1. Customer selects items.
  2. System calculates total.
  3. Customer confirms payment.
  4. Payment Gateway processes transaction.
• Alternate Flow: Payment fails → System prompts retry.

Role in Software Development:

• Serves as a requirements artifact for developers, testers, and stakeholders.
• Bridges business needs with technical implementation.

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2. Use Cases in Clean Architecture

Purpose:
To organize code by encapsulating business workflows as discrete, reusable components.

Key Traits:

• Code-Centric: Implemented as classes or functions (e.g., CreateUserUseCase).
• Single Responsibility: Each use case handles one specific task (e.g., user registration).
• Decoupled: Separates business logic from infrastructure (UI, databases).

Example:

class ProcessOrderUseCase {
  constructor(
    private orderRepository: OrderRepository,
    private paymentService: PaymentService
  ) {}
 
  async execute(orderRequest: OrderRequest) {
    const order = new Order(orderRequest.items);
    await this.paymentService.charge(order.total);
    await this.orderRepository.save(order);
    return order;
  }
}

Role in Software Design:

• Acts as the application layer in Clean Architecture, orchestrating domain logic.
• Promotes testability, maintainability, and framework independence.

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3. Use Cases in Project Management

Purpose:
To define project goals and deliverables in business terms.

Key Traits:

• High-Level: Focuses on outcomes, not technical steps (e.g., “Increase user retention”).
• Stakeholder-Aligned: Answers what the project will achieve, not how.
• Metric-Driven: Tied to success criteria (e.g., “Reduce checkout time by 30%”).

Example:

• Use Case: Streamline Checkout Process
• Objective: Reduce cart abandonment by 25%.
• Scope: Implement one-click purchasing.
• Success Metric: 20% increase in completed orders.

Role in Project Planning:

• Guides resource allocation, prioritization, and scope definition.
• Acts as a contract between stakeholders and project teams.

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What Do They Have in Common?

Despite their differences, all three interpretations share core principles:

1. User-Centric Focus

• UML: Models interactions between actors and the system.
• Clean Architecture: Encapsulates workflows triggered by user actions.
• Project Management: Aligns deliverables with user/business needs.

2. Structured Problem-Solving

All use cases break down complex processes into manageable scenarios:

• UML: Diagrams map flows and exceptions.
• Clean Architecture: Code enforces single-responsibility workflows.
• Project Management: Narratives define scope and success.

3. Bridging Gaps

• UML: Translates business requirements into technical specs.
• Clean Architecture: Connects domain logic with infrastructure.
• Project Management: Links stakeholder goals to execution.

4. Documentation & Communication

All three serve as communication tools:

• UML: Visualizes system behavior for developers.
• Clean Architecture: Self-documents code intent.
• Project Management: Aligns teams on objectives.

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Key Differences at a Glance

Aspect	UML	Clean Architecture	Project Management
Format	Diagrams/text	Code (classes/functions)	Narrative/docs
Audience	Developers, analysts	Developers, architects	Stakeholders, PMs
Scope	System interactions	Business logic	Business outcomes
Granularity	Scenario steps	Method/function level	High-level objectives

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When to Use Which?

1. UML Use Cases:

   • Ideal for requirements gathering and system design.
   • Use during early phases of software development.

2. Clean Architecture Use Cases:

   • Apply when structuring code for complex business logic.
   • Use in mid-to-late development phases.

3. Project Management Use Cases:

   • Deploy during project scoping and stakeholder alignment.
   • Use before development begins.

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Conclusion

“Use case” is a versatile concept, but its three faces serve distinct purposes:

• UML models system interactions.
• Clean Architecture organizes code around workflows.
• Project Management defines business objectives.

Their common thread is a focus on structured, goal-oriented scenarios—whether for designing systems, writing code, or delivering projects. By understanding these nuances, teams can avoid confusion and leverage the right type of use case for the task at hand.