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On Twitter, @ClearSpringBA asked:

@UMLguy to show a "parent" actor over subsidiaries, do I use the generalization feature in UML? (doing an actor-UC diagram, new to it)

Wordy cuss that I am, I answered multiple times:

@ClearSpringBA Are subsidiaries subordinates or special cases? For ex, Supervisor is special case of Employee; Emps are subordinates of Supv

@ClearSpringBA For special case, genralization arrow from Supv to Emp. "Supv is an Emp with more responsibilities."

Her questions back:

@UMLGuy thanks for all the info. subsidiaries are parent companies, can do everything on behalf of a sub.

UMLGuy so, i would draw the arrow toward the parent company? the arrow with the "big head", generalization arrow? prob wrong terms!

I decided this had gotten complex enough that words weren't working; so we went to email. Since this is general enough not to show any business info from her client, I thought I would share my response, in case anyone else finds it useful:

Here’s a simple diagram of business relationships:
Businesses as Actors
You can read it as follows:
  1. A Business is an Organization. Triangle arrow (“generalization” or “inheritance”) can be interpreted as “is a”.
  2. A Parent Company is a Business.
  3. A Parent Company has zero or more Subsidiaries, which are Businesses. (They might also be Parent Companies themselves, since a Parent Company is a Business.) The plain arrow can be interpreted as “has” or “contains” or “uses”. 0..* means any number, possibly 0. 1..* would mean any number, NOT 0. That could mean, for example, that a Parent Company MUST have at least 1 Subsidiary.
  4. A Business has 0 or 1 Parent, which is a Parent Company. The “topmost” Business has no Parent. All the others have 1.
  5. A Business has zero or more Partner Businesses.
I hope that clarifies things, and gets you thinking about new ideas. Please let me know if you have more questions.

And I hope it helps someone else, too!


Posted on Friday, December 5, 2008 1:58 PM It's all about communication. , UML | Back to top

Comments on this post: Business Actors

# re: Business Actors
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This is a great explanation, and even though I am not currently using UML, the diagram is understandable (with the explanations of course!)

Martin, is there any books you would recommend for getting started with UML for software architecture? My budget is my own out of pocket, and these pockets won't afford much more than books.
Left by Stacy Vicknair on Dec 05, 2008 3:12 PM

# re: Business Actors
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Practically my whole library is at the office today, and I'm not! I thought I had an architect-oriented UML book there, but I don't remember which one right now.

My own book, UML Applied: A .NET Perspective, starts with a requirements-and-architecture focused approach. I also have some old posts on this topic. And Scott Ambler's Agile Modeling touches a lot on the architecture world.

I'll look into this further. Please feel free to remind me, since I won't be back in the office before Monday.
Left by Martin L. Shoemaker on Dec 05, 2008 3:18 PM

# re: Business Actors
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A picture always helps explaining difficult things.
Left by paard on Dec 15, 2008 7:47 AM

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