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Use-case doubts [message #1780555]

Tue, 23 January 2018 21:10

Rafal Kisiel

Messages: 2
Registered: January 2018

Junior Member

Hi,
I want to enclose my use-cases in a rectangle with top left corner which specification and books mention about. There is a subject node on the palette but I can't get right shape. There's no topic on forum so I assume that there's a solution. Would you share with me how you cope with this?
I have another question. I've read in UML 2 for dummes that there is possibility to place scenarios on use-case diagram as instances of a use-case. It should looks like a regular use-case shape but its name should be underlined and as follows: ScenarioName:Use-caseName and connected with general use-case via dashed arrow. Is this supported by UML 2.5 and Papyrus?
Thanks for your time and answers.

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Re: Use-case doubts [message #1780650 is a reply to message #1780555]

Thu, 25 January 2018 09:44

Ri Fr

Messages: 134
Registered: July 2015

Senior Member

You can achieve what you want by placing text comments on the use case diagram. The rectangle is a system boundary and is used to show the scope of the use case model. Best practice for system boundary is to NOT use it. You will learn that in UML the most experienced and effective modelers use only a small part of UML... 80% of UML elements are for very specialized situations that you will not encounter when you are just beginning to use UML.
For more details on what I just typed read the very simple and short books "The elements of UML 2 style" and "Applying Use Cases: A Practical Guide (Addison-Wesley Object Technology Series)".
The golden rule for a good use case model: show only WHAT PEOPLE want to achieve WHAT RESULT. Show nothing on how the result is achieved (sequence diagrams are used to show how) and show nothing about what systems do. It's perfectly legal to show how and the systems in UML 2 use cases but it's not a good idea. The books explain why.

[Updated on: Thu, 25 January 2018 09:55]

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Re: Use-case doubts [message #1780664 is a reply to message #1780650]

Thu, 25 January 2018 14:13

Charles Rivet

Messages: 219
Registered: May 2014
Location: Canada

Senior Member

I agree with Richard Freggi's comments on this matter. "Applying Use Cases" is definitely a good read, and "Elements of UML2 style is useful - but, although not required, a knowledge of UML is definitely beneficial for the latter.

If you absolutely want to use the boundary (and I have met people who "absolutely" need it...), you best bet is to use a class, hide all its compartment save for name, scale it properly for use case, and make sure it's in the background. Note that this is a WORKAROUND and is NOT the right approach and I would NOT recommend a generalized use of that approach! However, I have had to take that approach in the past where it was the only solution I could find to address the client's requirement to show, on a single diagram, use cases from multiple systems in a "system of software systems" where UML was required by the client when SysML would have been a much better choice...

I would also like to mention note that sequence diagrams is one way to show the "how", activity diagrams is another one to do that. The choice of diagram to use will depend on many aspects, such as application domain, industry, client familiarity with diagrams, etc.

/Charles Rivet

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