Use Case Diagram Tutorial ( Guide with Examples )

Use case diagram is a behavioral UML diagram type and frequently used to analyze various systems. They enable you to visualize the different types of roles in a system and how those roles interact with the system. This use case diagram tutorial will cover the following topics and help you create better use cases.

Importance of Use Case Diagrams

As mentioned before use case diagrams are used to gather a usage requirement of a system. Depending on your requirement you can use that data in different ways. Below are few ways to use them.

  • To identify functions and how roles interact with them – The primary purpose of use case diagrams.
  • For a high-level view of the system – Especially useful when presenting to managers or stakeholders. You can highlight the roles that interact with the system and the functionality provided by the system without going deep into inner workings of the system.
  • To identify internal and external factors – This might sound simple but in large complex projects a system can be identified as an external role in another use case.

Use Case Diagram objects

Use case diagrams consist of 4 objects.

  • Actor
  • Use case
  • System
  • Package

The objects are further explained below.

Actor

Actor in a use case diagram is any entity that performs a role in one given system. This could be a person, organization or an external system and usually drawn like skeleton shown below.

Actor

Use Case

A use case represents a function or an action within the system. It’s drawn as an oval and named with the function.

Use Case

System

The system is used to define the scope of the use case and drawn as a rectangle. This an optional element but useful when you’re visualizing large systems. For example, you can create all the use cases and then use the system object to define the scope covered by your project. Or you can even use it to show the different areas covered in different releases.

System

Package

The package is another optional element that is extremely useful in complex diagrams. Similar to class diagrams, packages are used to group together use cases. They are drawn like the image shown below.

Package

Use Case Diagram Guidelines

Although use case diagrams can be used for various purposes there are some common guidelines you need to follow when drawing use cases.

These include naming standards, directions of arrows, the placing of use cases, usage of system boxes and also proper usage of relationships.

We’ve covered these guidelines in detail in a separate blog post. So go ahead and check out use case diagram guidelines >>.

Relationships in Use Case Diagrams

There are five types of relationships in a use case diagram. They are

  • Association between an actor and a use case
  • Generalization of an actor
  • Extend relationship between two use cases
  • Include relationship between two use cases
  • Generalization of a use case

We have covered all these relationships in a separate blog post that has examples with images. We will not go into detail in this post but you can check out relationships in use case diagrams >>.

How to Create a Use Case Diagram

Up to now, you’ve learned about objects, relationships and guidelines that are critical when drawing use case diagrams. I’ll explain the various processes using a banking system as an example.

Identifying Actors

Actors are external entities that interact with your system. It can be a person, another system or an organization. In a banking system, the most obvious actor is the customer. Other actors can be bank employee or cashier depending on the role you’re trying to show in the use case.

An example of an external organization can be the tax authority or the central bank. The loan processor is a good example of an external system associated as an actor.

Identifying Use Cases

Now it’s time to identify the use cases. A good way to do this is to identify what the actors need from the system. In a banking system, a customer will need to open accounts, deposit and withdraw funds, request check books and similar functions. So all of these can be considered as use cases.

Top level use cases should always provide a complete function required by an actor. You can extend or include use cases depending on the complexity of the system.

Once you identify the actors and the top level use case you have a basic idea of the system. Now you can fine tune it and add extra layers of detail to it.

Look for Common Functionality to use Include

Look for common functionality that can be reused across the system. If you find two or more use cases that share common functionality you can extract the common functions and add it to a separate use case. Then you can connect it via the include relationship to show that it’s always called when the original use case is executed. ( see the diagram for an example ).

Is it Possible to Generalize Actors and Use Cases

There may be instances where actors are associated with similar use cases while triggering few use cases unique only to them. In such instances, you can generalize the actor to show the inheritance of functions. You can do a similar thing for use case as well.

One of the best examples of this is “Make Payment” use case in a payment system. You can further generalize it to “Pay by Credit Card”, “Pay by Cash”, “Pay by Check” etc. All of them have the attributes and the functionality of a payment with special scenarios unique to them.

Optional Functions or Additional Functions

There are some functions that are triggered optionally. In such cases, you can use the extend relationship and attach an extension rule to it. In the below banking system example “Calculate Bonus” is optional and only triggers when a certain condition is matched.

Extend doesn’t always mean it’s optional. Sometimes the use case connected by extend can supplement the base use case. The thing to remember is that the base use case should be able to perform a function on its own even if the extending use case is not called.

Example use in this use case diagram tutorial

A use case with most of the scenarios found in use case diagrams

Use Case Diagram Templates

A use case template for an ATM system

A use case template for an ATM system

We’ve gone ahead and created use case diagram templates for some common scenarios. Although your problem or scenario won’t be exactly like this you can use them as a starting point. Check out our use case diagram templates >>.

Questions Regarding the Use Case Diagram Tutorial

We’ve tried to comprehensively cover everything you need to know about creating use case diagrams. If you have doubts about any section or can think of ways to improve this tutorial please let us know in the comments.

More Diagram Tutorials

Author

Nishadha

Software engineer turned tech evangelist. I handle marketing stuff here at Creately including writing blog posts and handling social media accounts. In my spare time I love to read and travel. Check out my personal blog Rumbling Lankan where I write about online marketing stuff.

Comments

  1. shital

    can we add conditions in use case diagrams? and how?

  2. xd

    how to name the actors?

  3. Leonardo Gulo

    Sir

    Can you create a use case diagram to build a web

    Where is the web that contains information about schools that exist in a region.

    And the website will provide information to the visitor such information facilities, achievements, tuition fees and others.

    thank you

  4. Shashank Gupta

    Great stuff. Quite neatly explained. Well done guys!

  5. simi

    hi there..can anyone help me to draw usecase diagram of specific case study.?

  6. keerthu

    i need a use case diagram for online tour guide system.can you please give an idea about that

  7. rec

    thanks,but still request to know more when to use <> and extend.

  8. Anupriya

    Hii..I need a usecase diagram for KYC…can anyone help me??

  9. xzanie

    Hello! ahm Can you create a hotel ,management system web-based use case diagram?

  10. Abhirami

    Need a use case diagram , sequence diagram,activity diagram,class diagram for secure message transmission using RGB and complex numbers. Pleaseeeeee Pleaseeeeee

  11. Abhirami

    need a use case diagram for secure message transmission using RGB and complex numbers. Please

  12. happiness

    please i need a use case diagram for a book trader system

  13. Dilantha

    good article. This helped me a lot to remember the things I learnt a year or two ago .. Thanks a lot… and keep up the good work !!!!

  14. Harsh Popat

    what about tertiary actors??

  15. Varma32

    Sir ..
    can You plz Give Me Use case Diagrames with Scinario

  16. sana

    hello sir,
    give me example of use case diagram for home furnishings ……..
    not furniture…
    plz send me as soon as possible..

  17. poojitha

    plz give me information about Use case description for get balance of point of sale termination

  18. irfanbanna srilanka)

    hi bro its very use full and please update with scenario and solution so that can be very use full first we do example our self then we can refer your answer .thanks

  19. jack

    Would you write about “Use Case Description” too.

  20. Yasith

    Bro, can you please create a SINHALA version of UML tutorial. 🙂

  21. FATEMA

    NEED UML DAIGRAMS(ALL) FOR COLLEGE ADMISSION SYSTEM

Leave a Comment

*
*

This blog uses premium CommentLuv which allows you to put your keywords with your name if you have had 9 approved comments. Use your real name and then @ your keywords (maximum of 3)
Back to top