Use Case Modeling

Definition

Use cases describe the interactions between the actors and the solution to achieve a goal. A use case describes the possible outcomes of an attempt to accomplish a particular goal that the solution will support. It details different paths that can be followed by defining primary and alternative flows.

Inputs

• A defined actor (user or system) and a specific goal that actor wants to accomplish
• Knowledge of system behavior, business rules, and any preconditions required before the interaction can begin

Outputs

• A structured description of the primary flow (the expected path to success) and alternative flows (exceptions, errors, edge cases)
• Clear preconditions and postconditions defining when the use case starts and what "done" looks like

When to Use

• Defining functional requirements for interactive systems where user (or system) behavior matters, not just data structure
• Projects where development teams need detailed, scenario-based specifications to build against
• Capturing exception handling and edge cases explicitly, not just the happy path

When Not to Use

• Purely data-oriented or batch-processing requirements with no meaningful user interaction
• Very early ideation stages where goals and actors haven't been validated yet