Anons I'm starting to see UML and I'm having problems with the abstraction. I can't define well the levels of detail allowed. Sometimes I see my teacher writes activities as Use case and others says it is not allowed, because a use case envolves the Activity, so I'm confused.

Could someone help me with my exercise please?, It is about the delivery process in a restaurant. We have made the Activity Diagram with the teacher, and he left us the Use Case Diagram , Sequence Diagram and Colaboration Diagram.

Also, I have been checking a book, it says that the relation between Actor and Use Case is by asociation (simple líne -), but my teacher uses an arrow (realize and comunicate), is it valid too? Thanks if someone can rewind my brain.

I'll post the diagrams I made next