Do I need to create a different use case diagram for my mobile app and for my web app? I have a mobile and a web app but mobile users cannot access the web application. Only the admins can do that.

  • 2
    Short answer: probably. But you haven't really told us anything about the app itself, so that's just a random person on the internets making a guess.
    – Dan Wilson
    Commented Oct 21, 2018 at 13:41
  • The mobile app sends a report or complaint. It is for passengers. Meanwhile, all reports are delivered to the web app. which is being managed by a government agency Commented Oct 21, 2018 at 13:47
  • Possible duplicate of How to show a sub system like mobile application in a Use Case Diagram
    – Christophe
    Commented Oct 22, 2018 at 10:59

2 Answers 2


A use-case diagram shows the high-level goals that users of the system want to achieve by interacting with the system. The use-cases shown in the diagram are on a comparable level of detail as system requirements and should not depend on the technology that gets used.

This means that the use-case for sending a report or the one for sending a complaint should not materially change when the design choice gets made to let the interaction run through a mobile app rather than a website.
This also means that the use-case diagram should not be split on the technology used to implement the use-case. Rather, if the diagram is to be split at all, it should be split such that related use-cases end up in the same diagram.


You have a couple of options here.

You can consider the subject of the use case diagram to be a system that is inclusive of both the mobile app and the web app. Your actors would be the different people or roles or personas who are using one of the two.

Alternatively, you can consider the subject of the use case to be each application. On each diagram, you would only have the actors that are using that application.

Since it appears that the actors that use each interface are different, I would lean toward creating a use case diagram for the mobile app that indicates the various actors who use the mobile app and what they can do and a use case diagram for the web application that does the same.

However, I'd be remiss if I didn't call out some words from Martin Fowler on use case diagrams:

Use cases appear in the UML in the form of use case diagrams, but these diagrams are of little value - the key value of use cases lies in the text which is not standardized in UML. So when you do use cases put your energy into the text.

In your particular case, use case diagrams may serve some value by providing a map to the use cases and making it easy to identify which applications provide which use cases to which actors. However, I would still focus on the textual or tabular representations of use cases - these are the things that would help developers and testers understand the user needs and build software far more than a use case diagram.

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