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capecod
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Registered: May 2001
Location: New York
Posts: 37

system thrashing: which diagram

23) A system undergoing performance testing is found to be "thrashing" (a condition that occurs when there is too much concurrency). Which of the following artifacts would be MOST helpful to uncover the problem?

a) The use case descriptions

b) A state diagram

c) A process view

d) An activity diagram

e) A collaboration diagram

Multiple Select - Please select all of the correct answers (this question has 2 correct choices).

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

This is a curious question. If I were investigating thrashing I would use a system tool like top (Linux) or Task Manager (W2K) or else I would use OptimizeIT for detailed performance analysis.

Thrashing itself is an ambigous statement. Does this mean that there is a lack of real memory and programs are swapping out to disk constantly? Or does this mean that threads or processes are CPU bound and contending for CPU resources? In either case, I would certainly want to use one of the tools listed above, and not a UML artifact!

Since this is a UML exam, however, I am forced to "play the game" and select:

D) An activity diagram - since this diagram can show concurrent processing then of course it could show concurrency problems.

C) A process view - since this sounds similar to the tools mentioned above. However, this is an odd name for an artifact since it is so open-ended.

The other diagrams seem to lack the ability to show contention for resources.

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Old Post 02-06-2002 03:51 AM
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kotiyal
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Registered: Feb 2002
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Hi,

I too am preparing for the 486 test for OOAD.

According to Fowler book ..Concurrency can best be dealt using State and Activity diagrams.

Correct me if I am wrong ?

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Old Post 02-08-2002 04:29 PM
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vadheraju
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Registered: May 2002
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Looks same to me..
Activity and State diagrams talk about Concurrency..
But what is Process View??
New "term" for me..........................

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Old Post 05-29-2002 04:49 AM
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capecod
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Registered: May 2001
Location: New York
Posts: 37

The best way I would describe "process view" is to run Task Manager on a Windows 2000 or XP system. Look at the Processes tab and sort by CPU. The process which is taking the most CPU resources is likely the one causing the system to "thrash".

What does this have to do with UML? Beats me! But the closest thing in UML would be a Deployment Diagram, which could be used to understand how the objects are deployed to running processes in real machines.

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Old Post 05-29-2002 12:58 PM
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Malachi
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Registered: Jun 2002
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There are specific tools for monitoring the processes in your project, similar to what capecod said about task manager.

As a side note C and D are correct.

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Old Post 06-06-2002 02:09 PM
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glennop
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Registered: Nov 2001
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I am puzzled by the proposed answer: c & d.

c) A process view

d) An activity diagram

What is a process view? I do not think that is a UML diagram, so this cannot be the answer.

"d" seems ok to me. An activity diagram shows parallel processing.

e) A collaboration diagram

This can also show async processing. "e" seems to be a better choice than "c".

So the answer should be d & e.

--glenn

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Old Post 06-19-2002 03:18 PM
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cfw
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Registered: Apr 2002
Location: ON
Posts: 92

The correct answers: "c" (Process view) and "d" (Activity Diagram).
The rationale for not using a State diagram is because it is mostly suggested to depict the behavior of a single object that you'd be particularly interested. Conversely, an Activity diagram would be suitable to depict flow of control (including parallel) that spans through multiple objects.
Regarding the Process View, the only reference I could find is from a presentation found on the web - Greg Schottlandís (Embracadero Technologies, Inc) tutorial:
Process View
- threads and processes that form the systemís concurrency and synchronization mechanisms
- addresses performance, reliability, scalability and throughput of the system
- static and dynamic aspects are captured as with the Design View with a focus on active classes that represent the processes and threads

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Old Post 06-19-2002 08:08 PM
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glennop
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Registered: Nov 2001
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Thanks for the information. I stand corrected. I did not see "process view" in uml distilled, so I thought it did not exist. However, I have a copy of Applying UML, 2nd ed, and see that there are two whole paragraphs on it. This is from a section on Architectural Views in the SAD.

(from p. 502)

<quote>
2. Process

- Processes and threads. Their responsibilities, collaborations, and the allocation of logical elements (layers, subsystems, classes, ...) to them.

- A view onto the UP Design Model, visualized with UML class and interaction diagrams, using the UML process and thread notation.
</quote>


on the next page is the following:

Process View

UML class and interaction diagrams illustrating the processes and thread of the system. Group this by thread and processes that interact. Comment on how the interprocess communication works

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Old Post 06-20-2002 12:47 PM
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cfw
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Registered: Apr 2002
Location: ON
Posts: 92

Thank you for the reference to Larman's book.

I have found additional reference to Process View from The Unified Modeling Language User Guide by the 3 amigos.
Process View
- encompasses the threads and processes that form the system concurrency and synchronization mechanisms. This view primarily addresses the performance, scalability and throughput of the system.
- Static aspects are captured using - Class and Object diagrams
- Dynamic aspects are captured using Interaction, Statechart & Activity diagrams.

According to the above description, Process View is a superset of all the diagrams mentioned in the question.

This is a fuzzy topic. I haven't found any good examples from these books nor have seen any usage from my projects.

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Old Post 06-20-2002 02:25 PM
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