Use Case Diagram with Database and Web Servers

Question

I'm finding it hard to get around my head how the specific scenario would work out:

I have a database server, a web server and a user.

When the user registers a service is created to the web server, the web server then goes to the database server and returns to the web server to register the details.

How would I actually illustrate this.

I have created the three Actors; User, Web Server, Database Server.

As a note I have read many online resources, and also a Book on UML.

Thanks in advance.

Answer 1

Are the DB/web servers part of the system you're implementing? If so you don't need them as Actors. UC Diagrams should only show actors outwith the scope of your system.

So you only need one Actor (User) in this case. The Use Case should describe the goal from the User's perspective (e.g. "Buy a Widget").

You could show the servers in a diagram showing how the UC is realised - usually a sequence diagram or activity diagram. Although I'd typically expect to see logical entities (classes) as well / instead of the physical servers.

hth.

Answer 2

I agree with maple_shaft's last statement. A high-level UC (use case) is a vehicle for capturing requirements.

Req'ts are the "what" of a system. What is the system supposed to do. What does the user need to accomplish. What interaction does the user need from the system.

By capturing system components in your UC you are injecting "how" into it and that's inappropriate for a UC. You don't want your use case to say how the system will accomplish something as that's an implemenation decision.