Week 2 - Use Case Diagrams Flashcards
What is the fundamental concept behind use case diagrams?
They express stakeholder expectations and are essential for detailed design in object-oriented development methods.
During which process are use case diagrams utilized?
They are utilized during the system analysis and design process.
What three main questions do use case diagrams answer?
1) What is being described? (the system)
2) Who interacts with the system? (the actors)
3) What can the actors do? (the use cases)
What are the components of a use case system diagram structure?
System, Actors, and Use Cases.
Are actors part of the system?
No, actors are outside the system boundaries.
How do actors interact with the system?
Through use cases or by being used by use cases, acting as a function for that use case.
Can actors adopt multiple roles?
Yes, actors can adopt and set aside multiple roles simultaneously.
What are the types of actors in use case diagrams?
Human and non-human (e.g., email servers). They can also be primary, secondary, active, or passive.
How are actors connected to use cases?
Via binary associations represented by solid lines.
What does an ‘Includes Relationship’ signify?
The behavior of an included use case is integrated into the behavior of another base use case.
What does an ‘Extends Relationship’ signify?
One extending use case may integrate with another base use case, but integration is conditional and not mandatory.
What happens in the generalization of use cases?
A use case inherits behaviors and relationships from another, and it can extend or override those behaviors.
Can abstract use cases be executed directly?
No, only the inheriting use case can be executed.
What does the generalization of actors allow?
It allows actors to inherit roles and communication abilities from other actors.
What are the key elements in the structured approach to use cases?
- Name,
- Short Description,
- Precondition,
- Postcondition,
- Error Situations,
- System State on Error,
- Actors,
- Trigger,
- Standard Process,
- Alternative Process.
What questions help identify actors in a system?
1) Who uses the main use cases?
2) Who needs system support for daily work?
3) Who is responsible for system administration? 4) Which external devices or systems does the system communicate with?
5) Who is interested in system results?
What questions help identify use cases?
1) What are the main tasks of an actor?
2) Does an actor want to query or modify system information?
3) Does an actor want to inform the system about external changes?
Why should use cases not model workflows?
Use cases focus on user interactions and not on processes or workflows.
Where are actors positioned in use case diagrams?
Outside the system boundaries.
What is the role of use case diagrams in object-oriented development?
They are essential for expressing stakeholder expectations and guiding detailed design.
How do actors provide functionality to use cases?
By acting as a function to the use case or directly interacting with the system.
Can an abstract use case define system functionality?
Yes, but it cannot execute directly; only inherited use cases execute.
What defines the boundaries between the system and external entities?
The system boundary, which positions actors outside of it.
Why are use case diagrams vital in stakeholder communication?
They express stakeholder expectations and are crucial for detailed design in object-oriented methods.
How do use case diagrams assist in system analysis?
They outline the system, its actors, and interactions, providing clarity during the system analysis and design process.
What does the ‘Includes Relationship’ in use cases integrate?
The behavior of an included use case into the behavior of another base use case.
Can an actor interact with multiple use cases simultaneously?
Yes, actors can interact with multiple use cases as part of their role.
What are the different categories of actors in use case diagrams?
Actors can be primary or secondary, active or passive, and human or non-human.
How do ‘Extends Relationships’ differ from ‘Includes Relationships’?
Extends relationships are conditional and independent, whereas includes relationships are integral to the base use case.
How are actors visually represented in relation to the system?
Actors are placed outside the system boundaries and connected to use cases via solid lines.
What kind of questions help identify external systems as actors?
Questions such as, ‘What external systems must the system communicate with?’ help identify such actors.
What must all use cases have to function properly?
They must be connected to at least one actor.
Can abstract actors be directly involved in a use case?
No, abstract actors represent roles or inherited capabilities and are not directly involved.
Why should use cases avoid modeling workflows?
Use cases are focused on user interactions, not the step-by-step processes or workflows.
What kinds of roles can an actor adopt in a use case diagram?
Actors can adopt multiple roles, functioning dynamically as needed within different use cases.
In what way do use case diagrams clarify system interactions?
By mapping the roles of actors, their interactions, and the system’s functionality.
What differentiates primary actors from secondary actors?
Primary actors benefit directly from a use case, while secondary actors do not.
When are extension points used in use cases?
They are used to define where the behavior of an extending use case integrates into a base use case.
What are the different Actor Types
Explain this Diagram
1.
Explain this Diagram
- Actors are connected to use cases
- Via association - always binary
- Solid Lines
- Actors must have at least one use case
- Multiplicities may be specified
Explain this Diagram
Explain this Diagram
- Shows an Extend Relationship
- A decides if B is executed
- Exetention points define at which point the behavior is integrated
- There are conditions which define when the behavior is integrated
Explain this Diagram
- A generalises use case B
- B inherits the behavior of A
- May extend or overwrite it
- B also inherits all relationships from A
- Adopts basic functionality of A
- Independently decides execution and changes from A functinoality
- B inherits the behavior of A
- A may be labeled {abstract}
- Cannot be executed directly
- Only B is executed
Explain this Diagram
- Generalisation of Actors
- Actors A inherits from actor B
- A can communicate with X and Y
- B can only communicate with X
Note
- Multiple inherited is permitted
- Abstract actors are possible
Explain this diagram
Explain this diagram
UC Issue information needs EITHER
One actor Assistent OR one actor professor for execution
Explain this diagram
UC that have the same objective must be grouped into one UC
Explain this diagram
Various steps are parts of the UC NOT seperate UC themselves
No functional decomposition
What does this show
What does this show
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