Use Case Diagram Tutorial

The purpose of a use case diagram in uml is to demonstrate the different ways that a user might interact with a system. In UML, use cases are diagrammed to be easily understood, no matter who is looking at the diagram. Our UML shape library in can help you create nearly any use case diagram using our UML diagram tool.

With Lucidchart's extensive UML shape library, it's easy to make use case diagrams of all types. Try it today!

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What is a Use Case Diagram

In the Unified Modeling Language, a use case diagram can summarize the details of your system's users (also known as actors) and their interactions with the system. To build one, you'll use a set of specialized symbols and connectors. An effective use case diagram can help your team discuss and represent:

  • Scenarios in which your system or application interacts with people, organizations, or external systems
  • Goals that it helps those entities (known as actors) achieve
  • The scope of your system

Employing Use Case Diagrams

Remember that a use case diagram doesn't go into a great deal of detail—for example, don't expect it to model the order in which steps are performed. Instead, a proper use case diagram depicts a high-level overview of the relationship between use cases, actors, and systems. Experts recommend that use case diagrams be used to supplement a more descriptive textual use case.

UML is the modeling toolkit that you can use to build your diagrams. With a use case diagram, the use cases are symbolized with a labeled oval shape. Lines represent actors in the process, and the actor's participation in the system is modeled with a line between the actor and use case. To depict the system boundary, draw a box around the use case itself.

What is a use case diagram in UML?

When to Apply a Use Case Diagram

There's no need to be confused about the relevance of use case diagrams. They're ideal in situations such as:

  • Representing the goals of system-user interactions
  • Defining and organizing functional requirements in a system
  • Specifying the context and requirements of a system
  • Modeling the basic flow of events in a use case

Use Case Diagram Components

To answer the question of "What is a use case diagram in UML?", you need to first understand its building blocks. Common components include:

  • Actors - the users that interact with a system. An actor can be a person, an organization, or an outside system that interacts with your application or system. They must be external objects that produce or consume data.
  • System - a specific sequence of actions and interactions between actors and the system. A system may also be referred to as a scenario.
  • Goals - the end result of most use cases. A successful diagram should describe the activities and variants used to reach the goal.

What is a use case diagram in UML?

Use Case Diagram Example

UML use case diagram example

Consider the example above. A man with a chain saw interacts with the environment around him. Depending on the situation and the context of the situation, he might fall into one of many different use cases. Does he seem to be on his way to work? Is there anything ominous about the way he is wielding his chainsaw? For example, if he is using the chainsaw in a non-occupational setting, we might have reason to think that he falls within the scope of "scary".

Use Case Diagram Symbols and Notation

The notation for a use diagram is pretty straightforward and doesn't involve as many types of symbols as other UML diagrams. Here are all the shapes you will be able to find in Lucidchart:

  • Use cases - Use cases are the horizontally shaped ovals. This represents the different uses that a user might need.
  • Actors - represented by stick figure people and are the people actually employing the use cases
  • Associations - represented by a line between actors and use cases. In a more complex diagram, it is important to know which actors are associated with which use cases. In the example above, the lines are simply drawn for the sake of consistency.
  • System boundary boxes - a box that sets a system scope to use cases. All use cases outside the box would be considered outside the scope of that system. For example, Psycho Killer is outside the scope of occupations in the example above.
  • Packages - A UML shape that allows you to put different elements into groups. Just as with component diagrams, these groupings are represented as file folders.

How to Draw a Use Case Diagram

See our guide on how to draw a Use Case diagram with Lucidchart here.

Use Case Diagram Template

Lucidchart is a great use case diagram tool for those who don't want to be tied to just one machine. It allows you to work on the go and backup your files online.

See additional use case scenario diagram templates here.

Use Case Diagram Examples

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