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SriSri
Junior Member

Registered: Oct 2004
Location:
Posts: 1

UML Newbie : Usecases

Hi,

I am new to UML and usecases.
How do we identify the usecases based on the requirements?
Do we need to have usecase for each requirment?

Say I have a requirment:

- I should be able to print the current window contents.

How can I write a usecase for that?

Can anybody give the outline of the usecase forn this requirement. Pre-Condition, Flow and Post condition.

-Sri

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Old Post 10-25-2004 04:55 AM
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Powdrhound
Junior Member

Registered: Apr 2004
Location: Wellington New Zealand
Posts: 10

When Identifying Use Cases take a step back and first identify your Actors.
At the end of the day without Actors wanting to achieve certain goals we don't have any use cases.

Once you have identified the Actor and identified the goal(s) they want to achieve you will be alot further down the track and in a good position to start identifying your use cases.

In your example

- I should be able to print the current window contents.

Theres a couple of options depending on how strict you want to be in your application of UML

You could add the fact that the content must be printable to your the use case that displayed what you want to print in the first instance

or

Use case name......... Print UI content

Actor ........................????

Pre-Condition............UI Content has been displayed to the Actor (this should/could be the post condition of the use case that displayed the content)

Post Condition..........UI Content has been successully printed

Flow.................
1. Actor selects to Print the current screen content
2. System Prints current screen content.
3. The use case ends


This may seem overly simplistic but use cases do not have to be complex and often in an a case such as this one they are anything but. Keeping it fairly generic especially in this instance will also enable you to easily facilitate re-use rather than writing a 'Print screen' use case for every screen you want to print.

I hope that helps

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Old Post 09-14-2005 10:11 PM
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vsatija
Junior Member

Registered: Oct 2005
Location:
Posts: 7

Hi,

I completely agree with Powdrhound. I would like to add more on how to identify use cases.

Following are few steps that forms the initial stage of writing use cases.
Identify Actors: These are persons/stakeholders/or any external system that interacts with our system.
Actors are categorized as Primary & Secodary. Sometimes to identify an actor you have to identify system boundaries so that anything external to the system and interacts with the system is an actor.
Identify main flows: Identify how actors interact with the system to achive a goal. This interaction leads to change in the state of the system. These flows are actually called a use case. We can break one flow into more than one use cases. It all depends upon the complexity of the use case.

One should always keep in mind that use case should be very simple to understand. The primary use cases identified form set of base use cases. These base use cases are explored in detail to form sub use cases.

I hope this is fine

Regards
Vipin Satija
vsatija

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Old Post 12-23-2005 09:17 AM
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