Software Engineering - Old Questions

10. Explain the use case diagram with example.

A Use Case consists of use cases, persons, or various things that are invoking the features called as actors and the elements that are responsible for implementing the use cases. The purpose of use case diagram is to capture the dynamic aspect of a system.

Use Case Diagram captures the system's functionality and requirements by using actors and use cases. Use Cases model the services, tasks, function that a system needs to perform. Use cases represent high-level functionalities and how a user will handle the system. 

Use case diagram consists of 4 objects:

1. System: System is used to define scope of the use case and drawn as a  rectangle.

2. Use Case: It represents the function or an action within the system. It is drawn as an oval and name with the function.

3. Actors: Actors are the users of a system. They interact with the system being designed in order to obtain some value from that interaction.

Relationships: Illustrate relationships between an actor and a use case with a simple line. For relationships among use cases, use arrows labeled either "uses" or "extends." A "uses" relationship indicates that one use case is needed by another in order to perform a task. An "extends" relationship indicates alternative options under a certain use case.