usecase question : can it be stand alone ?

Question

Hi

Im suppose to make a usecase diagram to a virtual school system:

Im doing well until I reached this :

" the student sign-in the system and do the entrance exam and then sign-out awaiting a response. at the end of the exam, THE SYSTEM calculates the notes and according to the final note IT SET the level for the student to inform himn with the results, the date to pay the fees and the class program. THE SYSTEM will also send the student information to the schools accounting system in order to calculate other fees and how to pay them. after paying the fees THE SYSTEM should modify the user (student) type from " student under registery" to student. "

now when its saying THE SYSTEM what should i do make a stand alone use case that is not connected (associated) with any actor ?! can i do that ?

and can anyone post links on examples , I found many but if you know a place where i can find a perfect examples please provide.

thanx in advance

Answer 1

In this sequence diagram, the curved arrow labelled runtests is a system action/operation. In your case, you can have a first lane for the user (student) and a second one for the system then describe you usecase as interactions (i.e. arrows) between the two lane or cyclic arrow pointing on the system.
See also this wikipedia page.