Use Case: Definition, Applications, Examples, and Considerations

A comprehensive explanation of 'Use Case', its various applications in different fields, examples, considerations, comparisons with related terms, and historical context.

A use case is a method for capturing the functional requirements of a system, particularly in software engineering, business process modeling, and systems engineering. It describes how different types of users (known as actors) interact with a system to achieve a specific goal. Use cases typically include a set of scenarios that illustrate the interactions between the system and actors, focusing on user-system functionality.

Structure of a Use Case

A use case usually comprises the following elements:

Title

The name or title of the use case.

Primary Actor

The primary entity (user or system) interacting with the system.

Goal

The objective that the primary actor wants to achieve.

Pre-conditions

Conditions that must be true before the use case begins.

Main Success Scenario

The narrative of the steps taken if everything goes as planned.

Extensions/Alternative Paths

Variations or alternative scenarios that might happen to achieve or not achieve the goal.

Post-conditions

The state of the system after the use case has been completed.

Applications of Use Cases

Use cases are applied in various fields such as software development, business analysis, and project management. They help in:

Software Engineering

Designing user interactions and system workflows by clearly defining system requirements from a user perspective.

Business Process Modeling

Mapping out organizational processes to identify and improve inefficiencies and understand user interactions with different system components.

Project Management

Providing a clear understanding of project requirements to stakeholders and helping in resource allocation and timeline estimation.

Examples of Use Cases

• ATM System Use Case:

  Title: Withdraw Cash

  Primary Actor: Bank Customer

  Goal: Withdraw a specific amount of cash from an ATM.

  Pre-conditions: The bank customer has a valid ATM card and sufficient balance.

  Main Success Scenario:

  1. The bank customer inserts the ATM card.
  2. The bank customer enters the correct PIN.
  3. The bank customer selects the “Withdraw Cash” option.
  4. The bank customer enters the amount.
  5. The ATM verifies the account balance and dispenses the cash.
  6. The ATM returns the card and prints a receipt.

  Extensions/Alternative Paths:

  • Invalid PIN entered three times locks the card.
  • Insufficient funds cancel the withdrawal process.

  Post-conditions: The bank customer’s account balance is updated, and the cash is dispensed.

• E-Commerce Platform Use Case:

  Title: Purchase Item

  Primary Actor: Online Shopper

  Goal: Purchase an item from the online store.

  Pre-conditions: The shopper is registered and has an active account.

  Main Success Scenario:

  1. The shopper logs in to the account.
  2. The shopper browses items and adds a product to the cart.
  3. The shopper proceeds to checkout.
  4. The shopper enters shipping details and selects a payment method.
  5. The system processes the payment and confirms the order.
  6. The system sends a confirmation email to the shopper.

  Extensions/Alternative Paths:

  • Cart empty prompts the user to add items.
  • Invalid payment method redirects the user to re-enter payment details.

  Post-conditions: The order is placed, inventory is updated, and the confirmation email is sent.

Historical Context

The concept of use cases was introduced by Ivar Jacobson in 1987, a pioneer in the field of software engineering. It became a popular tool with the advent of UML (Unified Modeling Language) and continues to be a cornerstone in requirements gathering and system design.

Comparisons with Related Terms

User Stories

While use cases describe the interaction in greater detail, user stories are short, simplistic descriptions of a feature from the end-user perspective often used in Agile methodologies.

User Scenarios

Similar to use cases but often less formal. They focus more on illustrating how users from various backgrounds might use the system.

FAQs

What are the benefits of using use cases?

Use cases help ensure that system requirements are captured from the user’s perspective, leading to more user-friendly systems. They also provide a structured format for documenting interactions, which aids in communication among stakeholders.

Are use cases only applicable to software development?

No, use cases can be applied in business process modeling, project management, and any field that involves defining system interactions and user goals.

How detailed should a use case be?

The level of detail in a use case should be sufficient to capture all necessary interactions and scenarios without getting too granular, overwhelming the reader with unnecessary information.

Can use cases change as the project progresses?

Yes, use cases are living documents and can evolve as project requirements and user needs change.

References

1. Jacobson, Ivar, et al. “The Object Advantage: Business Process Reengineering with Object Technology.” Addison-Wesley Professional, 1994.
2. Fowler, Martin. “UML Distilled: A Brief Guide to the Standard Object Modeling Language.” Addison-Wesley Professional, 2003.
3. Cockburn, Alistair. “Writing Effective Use Cases.” Addison-Wesley Professional, 2000.

Summary

In conclusion, use cases are a valuable tool in systems engineering and software development that help to capture user-system interactions clearly and effectively. By detailing pre-conditions, goals, success scenarios, and post-conditions, use cases ensure that all user requirements are adequately documented and understood, facilitating successful system design and implementation.