High Level Overview¶
Systems
Actors
Relationships
Use Cases
Use Case diagrams help explain interactions, or ideas.
Use case diagrams don't show a lot of detail but are good for communicating complex ideas in a basic way.
Systems¶
A System is whatever is being developed:
- Website
- Software Component
- Business Process
- Application
Systems are recognised as a rectangle and the label for the system is placed at the top for example "Banking App" defines this scope, anything inside the box happens in the banking app anything outside does not.
Actors¶
An actor is someone or something that uses the user to achieve a goal such as:
- An individual
- Organisation
- Another System
The most obvious actor for a banking app is Customer another actor wanted is the Bank which is going to provide information to feed into the banking app.
Things to keep in mind:
- Actors are external objects and need to be placed outside the system
- Actors need to be thought of as types or categories
Actors are not labelled by names, they are categorical.
Primary and Secondary Actors¶
Primary Actor - Initiates the use of the system
Second Actor - Reactionary
In the bank app example the primary actor is the customer, whereas the bank is the secondary actor. The bank will only act if the customer acts first, like withdrawing funds.
Primary actors to the left, and secondary actors to the left.
Use Cases¶
The Use Case represents an action that accomplishes some sort of task within the system.