Is there any case that log in or sign up can be a usecase in UML?

Question

I read that log in or sign up can't be a use-case.[Larman: Applying UML and patterns] Is there any case that log in or sign up can be a use-case in a project? How or where do you describe the sign up or the log in in your documentation if not as a usecase?

Answer 1

From a business perspective they are not use cases. Where is the value of a login? A login on a business level is nothing more than a constraint. You can attach that to the use case (e.g. «pre-condition» {must be logged on}).

On a technical level you can describe the login with a use case, though. You need to separate your model with respect to business and technical aspects. So as long as you do not mix both concepts, your model will be fine. Unfortunately UML has no "native" support for that. What I did in the past was to stereotype technical use cases with «tech».