![Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors). Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).](https://www.uml-diagrams.org/use-case-diagrams/use-case-diagram-elements.png)
Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).
![Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors). Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).](https://www.uml-diagrams.org/use-case-diagrams/business-use-case-diagram-elements.png)
Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).
![Example of transformation DFD diagram to UML use case diagram. | Download High-Resolution Scientific Diagram Example of transformation DFD diagram to UML use case diagram. | Download High-Resolution Scientific Diagram](https://www.researchgate.net/publication/44858981/figure/fig3/AS:307402038628356@1450301765786/Example-of-transformation-DFD-diagram-to-UML-use-case-diagram.png)