How to draw use case for two systems?

Question

I am new to business analyst. Currently I have a project that needs to communicate between systems. Based on my use case, I have 2 systems and 1 data centre.

Client A can use System1 and System2. If client A makes a withdraw through System1, System 1 needs to send the details to the Data Centre.

Client A also can make a withdraw through System2 and System2 needs to send the details to the Data Centre. The Data Centre is basically the place where System1 and System2 submit their details to. Of course, it has a rule that System1 and System2 can't send and receive the details directly without the Data Centre. Can I draw it out like this?

Answer 1

If you are after showing use cases, then there is only one you named Withdraw.

Use Cases show a single added value for an actor which is dealing with the system under consideration (SUC). From a business perspective you don't care about technical details. You will put that into requirements like { ATM must be used } etc. But you're actually only after the goal behind the UC in the first place. Next would be to describe scenarios how that goal could be achieved. Only then you care about (program) technic. Please also note that verb-only use cases are not a good choice. Use a predicate-subject(-object) form, so in your case Withdraw money.

That being said (I recommend reading Bitter/Spence about use cases as always) it rather looks like you are doing a technical documentation of an existing system. You can do that by showing devices

Note the multiplicity that says there's one data center and any number of ATMs. Now what actually happens between the components can be detailed by using sequence diagrams, using interfaces and things like that. Details are too many to be shown/explained here.

Answer 2

Your use case diagram is invalid, a use case diagram doesn't show exchanges, for that use a deployment diagram for instance :

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The Data Center is a secondary actor if is not part of your global system (contrarily to System1 and System2) :

If Data Center is part of your global system it doesn't not appear in the diagram because this is part of the implementation. The use cases show what must be done rather than how it is done.