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Topics - Paul D

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Uml Process / Hierarchical Decomposition of Use Cases
« on: March 25, 2003, 02:43:55 pm »
Hi All,

I've scoured all postings regarding use cases but can't find any explicit discussion of this...

Basically, I'm at the stage of use case modelling for a reasonably large website, and I'm trying to come up with the "best" / "correct" way to hierarchically decompose high level use cases in to sub-use cases. My only reference unfortunately is the excellent, though sometimes cryptic 'UML in a Nutshell' by O'Reilly [...looking at chapter 8 here].

I'm trying to find the right association/stereotype to define the relation between a superordinate use case and its immediate subordinate use cases. Working from the above text, my best guesses so far are: [Assuming that a use case 'X' is superordinate to use cases 'a', 'b', and 'c'...]

(a) There exist generalisation associations from a,b,c to x with the <<realise>> stereotype

(b) There exist dependency associations from a,b,c to x with the <<refine>> stereotype

(c) a,b,c are contained (directly) in a package, p, and there exists a dependency from p to x with a <<refine>> stereotype

(d) avoid using any form of superordinate use cases at all. All use cases are 'bottom level', and the hierarchy is imposed by using packages nested appropriately.

I don't like (d) for the simple reason that I would like to be able to describe 'general' high level tasks in use case form so that the client (and I!) can see the wood for the trees. Plus the O'Reilly text does suggest that there is a proper, UML compliant, way to do this.

I *know* I should buy a more prosaic text (and I will), but I'm in a bind at the moment, so if anyone has thoughts or ideas, I'd greatly appreciate them...


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