Study Cards on actor, system, actors
consider a computer keyboard and the monitor; they act as intermediaries between the end user and the computer system.
Unless you are designing the hardware, these devices are transparent, and they do not need to be Actors.
Instead, consider the end user as the Actor and consider the pass-through Actors as internal devices (or design elements) of the system under consideration.
Though uncommon, we can give Actors properties and give them associations to other model elements
The box and the stick figure notation are otherwise equivalent diagram elements.
Most modelers use the stick figure predominately
It is also useful if we wish to show the Actor’s properties.
As a Class box, it can be divided into compartments, showing attributes, operations, signals, and constraints.
What adornments can we have on a use case diagram?
However, we can use:
- multiplicity and
- arrowheads if they are necessary to clarify the situation.
- the arrowheads indicate which Actor contacts the system to start the Use Cases
- or if the Use Case contacts an Actor to start the behavior.
Note that once the Use Case is initiated, data and messages can flow in both directions irrespective of the direction of the arrow
We consider the other Actors as secondary Actors.
Why is it 0...1 and not 1?
As this is probably not legitimate, it would be preferable to show the multiplicity explicitly.
in the United States, the President signs bills into laws.
You would not use the President’s birth name as the name of the Actor, because as time goes on, we get new individuals in that role.
People may change their roles.
Manager at a company can change department or function.
How can we determine the goal of the external system?
Often, there is a representative of the external system that can answer questions to determine its goals as an Actor.
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