What is a Use Case? The Importance of Use Cases in Software Engineering

In the world of software development, a successful project is one that delivers a system that truly meets the users’ needs. But how do we define those needs and ensure everyone—from the developer to the project manager to the client—is on the same page? This is where the concept of a “use case” becomes invaluable.

A use case is a description of how a user interacts with a system to achieve a specific goal. It’s a fundamental technique in requirements engineering that focuses on the behavior of the system from an external, user-centric perspective. Think of it as a detailed story about how a person (or another system) uses your software.

The Three Core Components of a Use Case

At its heart, every use case involves three key elements:

• The Actor: The person, a group of people, or even an external system that interacts with your system. For an “ATM System,” the main actor would be the “Customer.” Other actors could be the “Bank,” which manages the accounts, or a “Maintenance Technician.”
• The Goal: The specific objective the actor wants to achieve. This is the “why” behind the interaction. For our “ATM System,” the goal might be “Withdraw Cash” or “Check Account Balance.” The goal is what drives the entire use case.
• The System: The software or product you are building. The use case describes how the actor interacts with this system to accomplish their goal.

By clearly defining the actor and their goal, a use case provides a simple yet powerful framework for understanding what a system should do.

Why Are Use Cases So Important?

Use cases are more than just a documentation artifact; they are a critical tool for communication and clarity throughout the software development lifecycle.

They Define the “What” from a User’s Perspective

Traditional requirements can often be a long list of technical features. Use cases shift the focus to the user. Instead of saying “the system shall have a login function,” a use case would be “Log In,” which describes how the actor (the user) interacts with the system to gain access. This user-centric view ensures that the final product is intuitive and solves real-world problems.

They Provide a Foundation for Testing

A use case description—which we’ll discuss in a future article—outlines the step-by-step process for a successful interaction, as well as alternative and error paths. This detailed flow provides a ready-made script for a tester to follow, making it easier to ensure all aspects of the system’s functionality are working as intended.

They Help Define the Scope and Identify Missing Features

By mapping out all the use cases for a system, a team can clearly define the project’s scope. This prevents “scope creep” and helps prioritize what to build first. Moreover, the process of creating use cases often reveals hidden requirements or overlooked scenarios (like what happens when a user enters the wrong password or a system error occurs), leading to a more robust and complete design.

They Facilitate Communication and Align Stakeholders

A well-written use case is a language that everyone can understand—from business analysts and clients to developers and testers. Business stakeholders can validate the requirements by reading the use case stories, ensuring that the system will work as they envision. Developers gain a clear understanding of the functionality they need to build. Testers can use the steps within a use case to design their test plans and verify the system’s behavior.

How to Get Started with Use Cases

Creating a use case model can be a daunting task, especially for a complex system. It requires careful analysis to identify all the actors and their goals.

With AI-powered tools like the Visual Paradigm Use Case Description Generator can significantly simplify this process. By simply providing a problem statement, our tool can analyze the problem, identify the essential use cases, and generate detailed descriptions for you. This allows you to focus on validating the requirements and refining the model, rather than spending hours on manual documentation.