Hi,
I have the following questions from IBM mock
test. I have the answers from previous posts on this site. But, I did not understand the answers to the following questions. I appreciate if someone would explain these answers.
1. What are the systems’s actors in the diagram, Figure Use Case?
a. Clerk, Manager
b. Clerk, Manager, Customer
c. Clerk, Manager, Bank network
d. Clerk, Manager, Bank network, Customer
Correct answer is d. In the exhibit, Customer is not linked to any of the use cases.
My question is, if an actor is not linked to any of the use cases, how do we know if he is a valid actor?
2. When creating a subclass, the:
a. selected superclass should be chosen because it has some methods the subclass can reuse, even if others do not apply.
b. Class name should normally be a qualification of its superclasses’ name
c. Subclass should be of the same type as all of its superclasses
d. Superclass should be marked as abstract
Correct answer is B and C. I understood that C should be the answer.
To some extent, I understand why A is incorrect: since it is a ‘is a’ relationship, all the methods of superclass should be reused by subclass. Please correct me if this is not the reason why A is incorrect.
But can somebody explain why B is the correct answer?Usually (like in
Java), class name is pre-fixed by its package name, not its superclass ! Can you give an example where A applies?
3. In an OO system, it is desirable to assign responsibilities:
a. relatively evenly across the classes.
b. More heavily in a few controlling classes.
c. According to interaction diagram messaging.
Correct answers are A and C. Can somebody explain why A is correct and B is incorrect?
Thanks