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SZ
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Registered: Apr 2001
Location: New York
Posts: 492

interaction diagrams

41) Which of the following are TRUE about interaction diagrams?

a) Interaction diagrams are at their best when they illustrate multiple scenarios.

b) Interaction diagrams are good at designing part or all of one use case's functionality across multiple objects.

c) Interaction diagrams are good for static modeling, since they fill out the classes and methods in the domain.

d) Interaction diagrams allow the analyst to show iteration and conditional execution for messaging between objects.

e) Sequence diagrams are logically equivalent to collaboration diagrams, differing primarily in format of presentation.

Multiple Select - Please select all of the correct answers (this question has 3 correct choices).

+++++++++++++++++++

Answers D and E seem to be pretty straight-forward.

A doesn't make much sense, really.

However, both B and C are reasonable answers. I can't seem to find an obvious fault with either.

I like answer C because this is one of the best outcomes of interaction diagrams - discovery of the methods on the objects in the problem domain.

But answer B is also quite good and is one of the chief activities defined by Larman in his book Applying UML.

Anyone for a coin toss?

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Old Post 02-13-2002 04:08 AM
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ram100475
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Registered: Dec 2001
Location: Little Rock, AR
Posts: 26

Smile My answer.

Hello SZ,

My answer is b, d and e

I am not choosing
a -> Interaction diagrams are good in describing a single scenario ( a single use case), still this is not a limitation of interaction diagram but just a concept tht generally people follow.
c -> Interaction diagrams represent dynamic modelling and not static modelling.

I am choosing
b -> As it is a best fit
d -> Yes interaction diagram represents iteration and conditions.
e -> is conceptually correct, in fact I should be able to turn a collaboration diagram to a sequence diagram (using some tools) with no effort.

I hope this helps. Please correct me if I am wrong.

Thanks
Ramakrishnan Seshadri.

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Old Post 02-15-2002 02:55 PM
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SZ
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Registered: Apr 2001
Location: New York
Posts: 492

This seems typical of where the IBM exam can be confusing. I count four correct answers although it says there are three.

The process of discovering methods on classes through the use of interaction diagrams - answer C - is well documented in Larman's Applying UML and Patterns.

Although on the surface this answer would appear wrong because an interaction diagram is focused on the dynamic model, nevertheless, the discovery of methods on classes is a major contribution to the static model.

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Old Post 02-17-2002 03:45 AM
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Stephen Hosking
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Registered: Nov 2001
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(c) is false, because it refers to domain model

I agree that (c) is confusing. What you say is true - Larman puts high value on interraction diagrams for assigning class responsibilites. However, I think that (c) is false because it refers to the domain (ie. domain model), whereas assignment of responsibilities through interraction diagrams takes place in the design model.

Note 1 - Larman's chapter 15, on interraction diagrams, is placed at the start of the design section.
Note 2 - Larman pg. 287 "Domain Model vs. Design Model Classes"

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Old Post 02-19-2002 12:48 AM
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SZ
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Registered: Apr 2001
Location: New York
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I see your point, Stephen, and as usual you are very precise.

However, do the authors of the IBM UML exam really expect people to detect these fine points?

If you really want to split hairs, the question says "fill out the classes and methods in the domain". I interpret this as, "later on in the design model, use interaction diagrams to fill out the methods for classes identified in the domain model".

Then again, I tend to read a lot into all these questions. Doesn't anybody else have this problem? The questions seem to always invite layers of interpretation.

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Old Post 02-19-2002 03:56 AM
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Stephen Hosking
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Registered: Nov 2001
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>> However, do the authors of the IBM UML exam really expect people to detect these fine points?

Yes. I think that the questions are designed to make us think about fine details like this. Don't be discouraged - there are plenty of easy questions in the real exam. There were many times when I did the practice exam that I thought a question was too subtle, but each time I eventually decided that the examiner knew exactly what they were doing, and that there was a "right" answer. (except the "business model and use cases" one )

This question is one those where someone who knows a lot can be worse off than someone who knows little. I think that you have to know a lot to even consider (c) as a possibility.

>> I interpret this as, "later on in the design model, use interaction diagrams to fill out the methods for classes identified in the domain model".
Yes again. But I don't think that this is "static modelling".

Thanks for the kind words, sz.

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Old Post 02-19-2002 09:48 AM
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sby
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Hi sz,

I think the answer to this question is in the first part of it:

c) Interaction diagrams are good for STATIC modeling, ...
(upper case is mine).

Interaction diagrams cannot be used for static modeling. They represent a dynamic model of the system.

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Old Post 02-20-2002 08:37 PM
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XMLViking
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Registered: Feb 2002
Location: Lake Oswego, OR
Posts: 10

I beg to differ.....

Can you not use static methods or Class methods for say validation, computations etc.....

I'm not sure why you may want to do this but you could. You woudl model the behavior using the Class name I'm assuming and then maybe a sterotype.

Anyone?

Eric

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Old Post 03-10-2002 06:47 PM
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sduskis
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Wink Mr. Viking: static vs. static

I think the word "Static" does not refer to class level variables and methods, rather it refers to UML diagrams that represent "static elements of design, such as classes, attributes and relationships" as opposed to dynamic UML diagrams that represent "dynamic elements of design such as objects, messages, and finite state machines" (Robert C. Martin Tuturial)

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Old Post 03-11-2002 04:00 PM
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sduskis
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sby vs. sz: What does "are good for" mean?

SZ, I guess you took "are good for" to mean that interaction diagrams help in constructing class diagrams, since interaction diagrams help in finding needed attributes and methods. This is what Larman talks about in his book.

SBY, I guess you took "are good for" to mean that interation diarams are used for constructing a static view of the model, which obviously they are not.

I see the ambiguity in the question that allows room for both interpretations, hence the need to "debug" and clarify the test. That is the purpose of this forum

However, given the continuation of the answer, I would guess that IBM meant SZ's interpretation, rather than SBY's interpretaion.

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Old Post 03-11-2002 04:06 PM
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sby
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Registered: Nov 2001
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You are quite right, but you misunderstood my words.

I quoted a question
"c) Interaction diagrams are good for STATIC modeling, ... "
and said that the answer is in this words. with the following explanation:
"Interaction diagrams cannot be used for static modeling. They represent a dynamic model of the system." Hence C) is NOT correct.

Sorry for confusion.

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Old Post 03-11-2002 07:17 PM
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sby
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XMLViking, you confusing static methods with a static modelling.

Static modelling is used to show structure and relationship.
Dymaic model shows interaction - objects, methods, change od states.

A static model might show you that some class has a staic function F(). Dymamic model tells what happans when this function is being called (messages sent, objects created, etc.).

regards

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Old Post 03-11-2002 07:25 PM
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sduskis
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SBY, while it is true that interaction diagrams cannot be USED as static diagrams (by definition), interaction diagrams ARE GOOD for static diagrams, because "they fill out the classes and methods in the domain."

The above is completely true, and is a benefit that Craig Larman ascribes to Interaction diagrams.

The term "are good" is ambiguous, and therefore can be interpreted your way or SZ's way. Each interpretation is valid based on the way the statement is present.

See SZ's reply to ram100475, which is the 3rd message in this thread.

Last edited by sduskis on 03-11-2002 at 09:11 PM

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Old Post 03-11-2002 09:07 PM
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garth
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I think "c" is wrong because you do not apply methods to the domain model. You apply them to the design model. Page 130 Larman.

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Old Post 03-22-2002 05:03 PM
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XMLViking
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You all must be right

I fully understand the differences between a static "Class" diagram and a dynamic Collaboration or Sequence Diagram.

I must have gotten the question out of context.

I'm very serious about that fact that sequence diagrams should be able to display Class methods.....

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Old Post 03-23-2002 03:55 AM
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