Use case diagram- database actor

Question

Should I enter as an use case: "Update database","Add to database" to my UML diagram? (The scenario: the user registers and then the credentials are added into the database) And if I have and external database for my project should I include it as an actor?

Answer 1

A defining feature of a Use Case is that it must deliver something that is end-to-end business-useful, ie it must represent something that is completely useful to the end-user. The oft-used example is an ATM —- “withdraw cash” is useful (and therefore a Use Case), whilst “enter PIN” is not on its own useful (and is therefore merely a function, not a Use Case, though it maybe a step in a Use Case). Given this —- how do you view your proposed Use Cases? Is “update database” itself completely useful, or is it a step in something else like “register User”? To answer your second question — it is unlikely that you'd have a database as an actor. Not impossible, but unlikely. It sounds like the “database” is part of your system, not an actor associated with it, but without more info. that's a guess.