Dobuts in Use Case Diagrams
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Posted By:   Sriram_Sundararajan
Posted On:   Thursday, April 10, 2003 04:09 AM

hi all

In the use case diagrams there are 4 main relationships between the use cases Include,extend,extenstion point and generalization.

Generalization is nothing but child usecan be substituted for its parent usecase whenever necessary

Include is the subtask of the usecase. say A and B are the main use case. If both A and B requires use case C we can include c as the subtask for A and B.

Can anybody plz explain me what is extend and extenstion point.


Re: Doubts in Use Case Diagrams

Posted By:   Anonymous  
Posted On:   Friday, April 11, 2003 12:38 AM

From the chapter "Use Cases" ("UML for Java Programmers" by Robert C. Martin):

Use case relationships fall into the category of things that "seemed like a good idea at the
time". I suggest that you actively ignore them. They’ll add no value to your use cases, or
to your understanding of the system, and they will be the source of many never ending
debates about whether or not to use «extends» or «generalization».

I tend to agree...

Re: Dobuts in Use Case Diagrams

Posted By:   Christopher_Koenigsberg  
Posted On:   Thursday, April 10, 2003 10:43 AM

My understanding:

A use case "UCA" can "extend" another, "UCB", without the other one's "knowing" about the first one. To do this, UCB defines "extension points", referring to spots in UCA, where there should be a new branch to new activities defined in UCB, followed by a return to the original sequence of activities in UCA, at the extension point. From the perspective of UCA, nothing unusual has occurred, but actually at the extension point, activities of UCB were "inserted".

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