In UML, use case diagrams model the behavior of a system and help capture the requirements of the system. Use case diagrams illustrate and define the context and requirements of the entire system or significant parts of the system.
Use case diagrams describe the high-level functionality and scope of a system.
These diagrams also identify the interactions between the system and its actors.
In UML, use case diagrams model the behavior of a system and help capture the requirements of the system.
You can use a single use case diagram to model a complex system, or create many use case diagrams to model the components / systems of the system. You will typically develop use case diagrams in the early stages of a project and refer to them throughout the development process.
