käyttökaaviot

Käyttökaaviot, known in English as use case diagrams, are a type of Unified Modeling Language (UML) diagram. They are used to represent the functionality of a system from the perspective of an external user. The primary purpose of a use case diagram is to illustrate the relationships between actors and use cases within a system.

Actors are entities that interact with the system. They can be human users, other systems, or even time. Actors are typically represented by stick figures in a use case diagram. Use cases, on the other hand, represent specific functionalities or services that the system provides to the actors. They are depicted as ovals.

The relationship between an actor and a use case is usually shown as a line, indicating that the actor initiates or participates in that particular use case. These diagrams help in understanding what the system is supposed to do and who will be using those functions. They are a valuable tool for requirement gathering and communication between stakeholders and developers.

Key components of a use case diagram include actors, use cases, and relationships. Relationships can also include extensions and inclusions, where one use case might extend another or include functionality from another. Use case diagrams are a high-level abstraction, focusing on the "what" rather than the "how" of system functionality. They are commonly used in the early stages of software development to define the scope and requirements of a system.