Introduction
The use case is a fundamental concept of many object-oriented
development methods.
Use case diagrams express the expectations of the customers/stakeholders
essential for a detailed design
The use case diagram is used during the entire analysis and design process.
We can use a use case diagram to answer the following questions:
What is being described? (The system.)
Who interacts with the system? (The actors.)
What can the actors do? (The use cases.)