Use Case

When designing software or digital products, how do you ensure the functionality meets user needs? A Use Case provides a clear answer. It’s a method used mainly in system analysis and requirements gathering. It describes a specific sequence of interactions between an external entity (an ‘actor,’ usually a user or sometimes another system) and the system being designed. This helps the actor achieve a specific goal.

Use cases outline how a user interacts with the system step-by-step. They include alternative paths and possible errors, capturing functional requirements from the user’s perspective. Use cases are essential blueprints for designing, building, and testing system behaviour.

What Are Use Cases?

Use cases focus squarely on functional requirements – outlining what the system must do to allow a user (or ‘actor’) to successfully complete a specific, valuable task. The core of a use case is the description of the step-by-step dialogue between the actor and the system.

Key aspects include:

• Goal-Oriented: Each use case is centered around achieving a specific, meaningful goal for the actor (e.g., “Place an Order,” “Generate Monthly Report,” “Reset Password”).  
• Actor Interaction: Describes the actions the actor takes and the corresponding responses from the system.  
• System Boundary: Defines what is considered part of the system being described versus the external actors interacting with it.
• Level of Detail: Use cases are often more detailed and structured than related concepts like scenarios or user stories, typically outlining preconditions, postconditions, and multiple flows (success, alternatives, exceptions).

Use Cases vs. Related Concepts:

• Scenarios: Provide narrative context, user motivation, and a high-level story of interaction, often serving as inspiration before writing detailed use cases. (See our article on Scenarios).
• User Stories (Agile): Offer a concise requirement from the user’s perspective (“As a [user type], I want [goal] so that [benefit]”). A use case might detail the specific interactions needed to fulfill that user story’s ‘want’.  
• Feature List: Simply enumerates system capabilities without describing the interaction flow or user context needed to achieve a goal.

Use cases bridge the gap between high-level user needs and detailed functional specifications.  

Common Elements of a Use Case

While various templates exist (e.g., those by Alistair Cockburn or UML standards), a typical use case description includes elements like:

1. Use Case Name: A concise, action-oriented name reflecting the actor’s goal (e.g., “Submit Timesheet”).  
2. Actor(s): The primary actor initiating the use case (e.g., “Employee”). Secondary actors (e.g., “Approval System”) might also interact.  
3. Goal/Objective: A brief summary of what the primary actor intends to achieve.
4. Preconditions: What must be true before the use case can start (e.g., “Employee is logged into the system,” “Current timesheet period is open”).  
5. Trigger: The specific event that initiates the use case (e.g., “Employee selects ‘Submit Timesheet’ option”).  
6. Main Success Scenario (Basic Flow): A numbered list detailing the step-by-step interaction between the actor and the system for the ideal, successful path to achieving the goal. (e.g., 1. Actor enters hours for each day. 2. System validates hours. 3. Actor clicks ‘Submit’. 4. System confirms submission and notifies manager).  
7. Alternative Flows (Extensions): Describes variations or optional paths within the main flow (e.g., Actor saves draft, Actor adds overtime hours requiring justification).
8. Exception Flows (Error Handling): Details how the system handles errors or conditions that prevent successful completion (e.g., Invalid data entry, system connection lost, timesheet rejected).  
9. Postconditions: What must be true after the use case completes successfully (e.g., “Timesheet status is ‘Submitted’,” “Manager is notified”) or fails (e.g., “Timesheet remains in ‘Draft’ status”).  
10. Optional Details: Frequency of use, priority level, performance requirements, related business rules, non-functional requirements.  

Why Use Cases Matter in Defining System Functionality

Use cases play a valuable role in the requirements, design, development, and testing phases:

• Clarify Functional Requirements: Provide a detailed, unambiguous description of what the system must functionally support from a user interaction standpoint.
• Maintain Focus on User Goals: By structuring requirements around achieving specific actor goals, they help ensure the system is built to deliver user value.
• Improve Communication: Offer a structured format that can be understood by diverse stakeholders – business analysts, UX designers, developers, QA testers – facilitating clearer communication about system behavior.
• Guide Design and Development: Serve as direct input for UX/UI designers creating the interface flows and for engineers implementing the underlying logic and system responses.
• Foundation for Testing: The main success scenario, alternative flows, and especially exception flows provide clear, actionable input for writing functional and user acceptance test cases.
• Manage Complexity: Explicitly documenting alternative paths and error conditions helps manage complexity and ensures these less common but important interactions are considered.  
• Define Scope: Help delineate the functional boundaries of a system, module, or release by defining the set of goals the system enables users to achieve.

Using Use Cases: Balancing Detail with Agility

While valuable, the use case methodology has benefits and considerations:

Benefits:

• Provides detailed, structured descriptions of functional requirements centered on user goals.  
• Systematically captures main success paths, alternative flows, and error conditions.  
• Facilitates clear communication and shared understanding across different teams.
• Excellent input for interface design, backend development, and test case creation.
• Helps manage system complexity and define functional scope effectively.  

Considerations & Potential Pitfalls:

• Can Be Time-Intensive: Writing comprehensive, detailed use cases for all interactions in a complex system requires significant analytical effort upfront.
• Risk of Premature Design: If written too prescriptively, especially regarding UI specifics, they might constrain design exploration rather than just defining functional needs. Focus should be on what the system does in response to the actor, not precisely how the UI looks.
• Potential for Complexity: Very detailed use cases can become lengthy and difficult to maintain, especially in rapidly changing environments.
• Focus Primarily on Functionality: They excel at describing system behavior but don’t inherently capture non-functional requirements or the qualitative aspects of the user experience (e.g., usability heuristics, emotional response, visual appeal). They need to be complemented by UX design and research.
• Adaptation for Agile: While goal-oriented thinking is valuable, creating exhaustive, detailed use case documents upfront can sometimes clash with Agile principles favoring iterative development and emergent requirements. Lighter-weight versions or focusing on key flows might be more suitable in some Agile contexts.
• Requires Skill to Write Well: Crafting clear, consistent, and appropriately detailed use cases takes practice.

Use Cases as Functional Blueprints for Interaction

Use cases are a common method to define and share functional requirements. They show step-by-step interactions between users (actors) and a system to achieve specific goals. Use cases help us grasp system behaviour, including main success paths, alternatives, and error handling. They are an important link between business analysis, design, development, and testing.

Use cases focus mainly on what the system should do. The goals they describe must be based on a good understanding of user needs and tasks. This understanding often comes from UX research methods, which platforms like Userlytics facilitate. After a design based on use cases is created, Userlytics is the perfect platform for usability testing. It checks if users can easily and effectively complete the described interactions in real life. While the detail level needs careful thought, especially in agile settings, use cases remain a strong tool. They help create clear functional blueprints to ensure systems truly support users in achieving their goals.