UML

A use case diagram is a Unified Modeling Language (UML) diagram for requirements elicitation. Use case diagrams provide a graphical overview of the goals (modeled by use cases) that users (represented by actors) want to achieve by using the system. Use cases in a use case diagram can be organized and arranged according to their relevance, level of abstraction, and impact on the user. They can be linked to show their dependencies, include, extend, generation relationships.