![UML dependency is directed, supplier-client relationship which shows that some element requires other model elements. UML dependency is directed, supplier-client relationship which shows that some element requires other model elements.](https://www.uml-diagrams.org/dependency/dependency-overview.png)
UML dependency is directed, supplier-client relationship which shows that some element requires other model elements.
![4.4 Dependencies :: Chapter 4. Use-Case Diagrams :: Part II: Structural Modeling :: Learning UML :: Programming :: eTutorials.org 4.4 Dependencies :: Chapter 4. Use-Case Diagrams :: Part II: Structural Modeling :: Learning UML :: Programming :: eTutorials.org](http://etutorials.org/shared/images/tutorials/tutorial_8/Luml_0405.gif)
4.4 Dependencies :: Chapter 4. Use-Case Diagrams :: Part II: Structural Modeling :: Learning UML :: Programming :: eTutorials.org
![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).
![Formalize Your Domain Model With a Use Case Diagram - Apply a Domain-Driven Design Approach to Development - OpenClassrooms Formalize Your Domain Model With a Use Case Diagram - Apply a Domain-Driven Design Approach to Development - OpenClassrooms](https://user.oc-static.com/upload/2019/11/12/15735641091081_2c1%20Patron%20librarian%20newly%20added%20use%20case%20OVAL-01.jpg)
Formalize Your Domain Model With a Use Case Diagram - Apply a Domain-Driven Design Approach to Development - OpenClassrooms
![1 Use case diagram of an intelligent WDN. The CPS agent is the actor in... | Download Scientific Diagram 1 Use case diagram of an intelligent WDN. The CPS agent is the actor in... | Download Scientific Diagram](https://www.researchgate.net/profile/Sahra-Sedigh-Sarvestani/publication/226298189/figure/fig1/AS:393816503799816@1470904579442/Use-case-diagram-of-an-intelligent-WDN-The-CPS-agent-is-the-actor-in-the-use-case.png)