> For the complete documentation index, see [llms.txt](https://dotnetweb30-ke.gitbook.io/ke/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dotnetweb30-ke.gitbook.io/ke/design/modeling/uml-use-case-diagram-essentials.md).

# UML: Use Case Diagram (Essentials)

Use cases are a technique for capturing the functional requirements of a system. Use cases work by describing the typical interactions between the users of a system and the system itself, providing a narrative of how a system is used.

{% hint style="success" %}
A **scenario** is a sequence of steps describing an interaction between a user and a system
{% endhint %}

![](https://3408508746-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lis5JLcnSD2vdYdyQ3U%2F-LjCXL0NfwbZJDQEtzZk%2F-LjCYi5hB-fpedV6qKBZ%2Fuse-case-diagram.png?alt=media\&token=01e059fa-d3d4-49f9-9f47-42d7e255559b)

{% hint style="success" %}
A **use case** is a set of scenarios tied together by a common user goal.
{% endhint %}

In use case–speak, the users are referred to as actors. An actor is a role that a user plays with respect to the system. Actors might include customer, customer service rep, sales manager, and product analyst.

![](https://3408508746-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lis5JLcnSD2vdYdyQ3U%2F-LjCXL0NfwbZJDQEtzZk%2F-LjC_4e2v9JKNP8nWXtZ%2Fuse-case-diagram-2.jpg?alt=media\&token=a66cad6a-9472-4ae1-a35e-39fb02f91aee)