Use Case Association - Quiz Explanation

The correct answers are indicated below, along with text that explains the correct answers.

 
1. An actor is
Please select the best answer.
  A. A person
  B. A job title
  C. A role
  D. A system
  The correct answer is C.
An actor is a role. Use cases attempt to put distance between the conceptualization of the system and the current implementation. A and B are incorrect because references to current people or job titles would be too implementation specific. D is incorrect because an actor could be a person or a device, as well as a system.

2. The system icon identifies
Please select the best answer.
  A. The boundaries of the system
  B. The scope of the project
  C. The context of the system
  D. Another system in the role of an actor
  The correct answer is C.
The system icon identifies the context of the system. The purpose of the icon is to place the system in a visual context relative to the actors who will use the system and the features that the system must contain. A is incorrect because a boundary apart from the relationship with the actors is insufficient to define the system's purpose. B, although important, is not accomplished by the system icon. The scope usually requires additional documentation in text form. D is incorrect because systems in the role of actors use a different icon and are positioned next to the system icon and associated with use cases within the system icon.

3. A person may function in
Please select the best answer.
  A. Only one role
  B. Many roles
  C. One role per system
  D. One role per use case
  The correct answer is B.
A person may function in many roles. A person may perform many different functions and use the system in many different capacities when using a system. There really is no limitation other than the nature of the problem domain to restrict the possible number of roles that a person may play. The same person may even use the same use case from different roles. Thus A, C, and D are incorrect.


4. Devices and other systems
Please select the best answer.
  A. May be actors
  B. May only receive output from a use case
  C. May only provide input to a use case
  D. Are out of scope because we are describing only one system at a time
  The correct answer is A.
Devices and other systems may be actors. Actors may be people; systems or devices; or anything or anyone who needs to use the system for input, output, or both. There is no restriction on the interactions based on the kind of actor, so answers B and C are incorrect. People, systems, and devices may all function as actors in relation to our system, so D is incorrect.

5. Associations
Please select the best answer.
  A. May exist only between actors and use cases
  B. Identify the flow of data between actors and use cases
  C. Identify interactions between actors and use cases
  D. Identify dependencies between actors and use cases
  The correct answer is C.
Associations identify interactions between actors and use cases. Associations simply indicate that there is some sort of communication, no matter what that communication is. To get the details, you need to look at the use case narrative or one of the other models such as the sequence or collaboration diagrams. A is incorrect because use cases may interact with one another. B is incorrect because the association has no way of showing the data flowing between the two elements. D is incorrect because there is a different notation for dependencies, and dependencies appear in other diagrams that we haven't yet described.

6. Use cases
Please select the best answer.
  A. Identify business processes
  B. Identify system goals
  C. Describe workflow
  D. Prioritize system procedures
  The correct answer is B.
Use cases identify system goals. Use cases are specifically designed to avoid dictating the process or the solution as to how the system will achieve a goal. Use cases leave that to the rest of the modeling effort. Use cases only set the target for the solution process, which is why they translate so well into test cases for the rest of the project. Because use cases do not specify solutions, only goals, answers A, C, and D cannot be correct.


7. The association stereotype <<Uses>> indicates
Please select the best answer.
  A. The target use case is a subprocess of the source use cases
  B. Delegation of part of a task to another use case
  C. A specialized form of a use case
  D. An alternative form of a use case
  The correct answer is B.
The association stereotype <<Uses>> indicates delegation of part of a task to another use case. A is incorrect because this is similar to calling a subprocess, but subprocess implies a process that does not stand alone and cannot be used independent from the calling process. "Used" use cases are typically autonomous use cases that may also be referenced much like you would ask help from a friend. C refers to the <<Extends>> stereotype, where one use case is a variation on another use case, a special case that accomplishes the same goal under slightly different circumstances and/or in a slightly different way. D is incorrect because the <<Uses>> association stereotype is not an alternative form of a use case.

8. The association stereotype <<Extends>> indicates
Please select the best answer.
  A. Delegation of part of a task to another use case
  B. The target use case is a subprocess of the source use cases
  C. A specialized form of a use case
  D. A deviation from the UML standard
  The correct answer is C.
The association stereotype <<Extends>> indicates a specialized form of a use case. A is incorrect because delegation is expressed with the <<Uses>> stereotype. Use cases do not use subprocesses, so B is incorrect. D is incorrect because stereotypes are provided as a part of the UML standard and are used to extend its interpretation, not modify its meaning.