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Another Question from IBM 486 Test

 
Greenhorn
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State diagrams:
a) are good at depicting the behavior of an object across multiple use cases.
b) are best used for objects that have multiple interesting states and not for most or all the objects in the system.
c) are good at depicting interactions among multiple objects.
d) can be used for user interface or control objects.
Answers from IBM are a, b & c. a & b are reasonable, but why c? Could interface have several states? what interface can have just
some operations, right?
Naichen
 
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Naichen, I would say:
true a) ... or that, are good at depicting the behavior of an object across ONE use cases, too. I guess what that emphasis is the importance of organization all development efforts around use ceases.
true b) state diagrams describe the states of particular object so it might be an overhead to create them for all the objects in the system, event this with little number of uninteresting states. Honestly I am not sure what is this question suppose to test?
false c) again, state diagrams describe the states of ONE object
true d) why not, user interface or control objects are as good as any.
>> Could interface have several states?
I would thing so, but it would be rather states of an object implementing this particular interface. If it is "very interesting" (read complicated) interface it would make perfect sense to have state diagram focused on it.
>> what interface can have just some operations, right?
I am not quite certain if I have understood You but if you asking if interface can have attributes, the answer is positive, otherwise dealing with concepts like Java interfaces would be rather complicated.
 
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So are these actual questions from the IBM test? Where did you find them?
 
Michal Harezlak
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Matt:
I recall them from a IBM's pre-assessement/sample test.
 
naichen
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Michal,
If we can use state diagram for interface, then what's difference
between interface and object? i think only object can have state. it would be ok if the question say that we can draw state
diagram for object which realize some interfaces.
Naichen
 
Michal Harezlak
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It would be ok if the question say that we can draw state diagram for object which realize some interfaces. I think it would be OK, but the interface is a role that given object can play, and objects of different classes (types) can implement the same interface. Introducing object into Interface state diagram would be a little bit like introducing irrelevant information (perhaps not in all cases) into the picture. Both Interface and Object represent operations and attributes, object is a physical entity of particular class when interface can be implemented by particular class. Try to think about it as a model. Using analogies from programming languages is not always the best approach. You are not testing physical entities (like a physical object in the computer system ), all what you are trying to achieve is assessment of usefulness of particular solution to the problem. Are you referring to some actual question?
 
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then what's difference between interface and object?


That sounds like a misunderstanding of the question. When option d says "user interface" it refers to a GUI, not an interface in the object-oriented sense.
I would agree with Michal that A, B and D appear correct.
How were you able to obtain IBM's answers to the question? When I ran through the preassessment test it only gave overall results at the end (not feedback on individual questions).
 
Michal Harezlak
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Greg:
I guess the trick would be to answer just one question and grade the test ;-).
 
Greg Whelan
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Yeah, with the responsiveness of their server (at least when I tried it), that would not be a whole lot of fun
And then there's the first time I ran through the simulator -- it crashed (I got a screen with a Java stack trace) when I was 2 questions away from finishing!
 
Michal Harezlak
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Greg:
I agree the ICE server suck. I used to do lots of Java test there, it used to work good in the morning.
 
naichen
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Yes, I didn't pay attention to <bold>user</bold> interface, which
may be GUI or other concrete classes. sorry.
Naichen
 
Michal Harezlak
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Sorry Naichen, I have not realize what you wear asking about.
 
Michal Harezlak
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Originally posted by naichen:
State diagrams:
...
d) can be used for user interface or control objects.
...


I came across this statement: "Many people find that UI and control objects have the kind of behavior that is useful to depict with a state diagrams." in the M. Fowler's book. It looks like Mr. Fowler's book is a true Bible for this exam, doesn't it?
 
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