Peruskäyttötapaus

peruskäyttötapaus (Finnish: basic use case) is a concept used primarily in software engineering and systems design to describe a fundamental scenario in which an actor (user or external system) interacts with a system to achieve a concrete goal. It captures the essential steps and required conditions for a particular function, providing a focused blueprint that is easier to understand, implement, and test compared to more elaborate use cases.

In practice, a peruskäyttötapaus focuses on the minimal sequence of events needed to complete a business objective. It excludes optional or alternative flows, error handling, and contextual variations that may appear in a full use case diagram. By isolating the core interaction, developers and analysts can verify the correctness of the main functionality before adding layers of complexity.

Typical structure of a peruskäyttötapaus includes: the initiating actor, the system’s primary response, and the final state of the system after completion. It often serves as the building block for higher‑level use cases. In agile environments, it supports incremental development; tests are written for the basic scenario first, then extended to cover edge cases.

The term originates from the use‑case modelling techniques introduced by Ivar Jacobson and Karl Wiegers and has been adapted in various methodology frameworks, such as Unified Process and Domain‑Driven Design. While peruskäyttötapaus is a Finnish expression, the concept aligns closely with the English “basic use case” or “primary use case.”