UML Use cases diagram system representation

Question

How are you?. I am making this question because I am developing the architecture of a mobile app. I am making an Use cases diagram and I need to represent the system inside that diagram. For example, User needs to ask to the app for some kind of information. The use case would be called information query, and the actors that intervene are User and System. How can I represent the System?. Is it the same way like an human actor?, the same symbol?. Or there is another way to represent this. Thank you so much!.

Answer 1

• Honestly, there are a lot's of post about UC on stack overflow to guide you, see also on the net: sparx tutorial or papyrus tutorial

The goal of the use case diagram is not to model the system but what the system does for the actors. It is always a description as a black box.

The system boundary which can be model is not an UML object, i mean there is no "SystemBoundary" meta-class.

So usually, i do :

• Think to all elements which interacts with your system (human and not human) : this is the actors. It is safer if you are able to fill a table with actor name and actor role. Like that you are sure that you know why you define an actor.

• Draw a schema with actors only to show inheritance relations to model the different roles of your system.

• Think to what these elements needs to perform, and there are a lot's of post about this point on stack overflow. As @Kilian would say: do not think in terms of functions or workflow but more in terms of features or needs. Like for actors, it is safer to be able to fill a table with all use cases and primary actor and a short sentence sum up the use case.

• Then draw your diagram .

• Do not forget to use corectly include and extend relationship.

• Goog luck ;)

Answer 2

There are two possibilities, depending on if you are interested in the insights of the system or not. If not, then use a just an actor. If you want to dinstinguish it from (human) users, then you can define a stereotype and assign it to it. If you care for the system, ie, it is an ohter subsystem of your system, then you can use a second system boundary in the use case diagram and show the use cases of the other subsystem in the system boundary box, which represents it.