The UML language gives us some simple graphical elements to represent the key ideas.

For example, a UML Use Case diagram looks like this:
Normal use cases I find that diagrams like this really don’t need explaining, even to non-UML readers.

Maybe I might have to say that the blue oval is a ‘story’ of how something gets done, but the rest is fairly obvious:

  • Some actors are involved in some Use Cases, and
  • a couple of the Use Case include another one.

But you might not know that this use of these shapes is optional. UML also says we can use a simpler ‘rectangle’ notation if we want:use case boxes

Using this notation style doesn’t seem quite as obvious. The tool which I used for the diagrams – EA – helpfully added some default colors to the diagram, which I have removed, just to make the point that I don’t think this diagram is anything like so immediate. A box which says <<Actor>> doesn’t seem so obvious as one which has a stick-person. Which is why I have never seen a UML Use Case diagram use the rectangle notation.

So why use Rectangles ?

This use of the simple rectangle notation is taken to the extreme by Archimate. Most examples from that language seem to use the rectangle notation exclusively, even when it might give the reader a clue as to what’s being modelled:

Archimate boxes An Archimate example, taken from the Open Group specification for Archimate. They are saying that:

  • There are three Business Actors: the luggage, medical insurance and sales department
  • Two of them take the respective Business Roles of Luggage Insurance Seller and Medical Insurance
  • There are some Business Collaborations, where these Roles and Collaborations get together to done something (not specified here)

The equivalent diagram using the non-rectangle notation looks like this:Archimate cartoons

I think that this diagram is easier to read than the one above. Apart from the disappointing visual pun of the ‘role (roll)’, the other two bits of notation seem sensible: the Business Actor looks like a person ,and “collaboration” as of two overlapping circles seems sensible.

I realize that in taking this view, I’m making myself into a  “Mickey-mouse”, child-like modeller. Gerben’s book (Mastering Archimate) comes out really, really strongly against this notation style, and in favour of the simple rectangle:

In my view, these forms are for children, not grown-ups..” and suggests that if I want to use this style, I should go the whole way and “..create a funny drawing with Greek columns, jumping dogs...” (you see, Gerben – I really DID read your book..:-) )

…which is a shame, because I really think that the more visual cues we give our readers, the easier they will find it to understand what we’re trying to say. Like Gerber, I believe PowerPoint and Visio, and especially ANY kind of clip-art are death to modeling, but these aren’t those kinds of random images: they are part of an industry-standard notation, which will be the same no matter who draws it.

Perhaps this is why I found Gerben’s book such a hard read. He does use a consistent color scheme for the Archimate layers, but uses the rectangle style for the boxes, which seems to make the diagrams very similar to each other. Even though they are saying very different things. And all the boxes are deliberately the same size, which means he can’t use the obvious abstraction of ‘big box = big thing’.

So i’m going to stick with my ‘child-like’ modelling, and use the non-rectangle notation.

I never wanted to be a grown-up anyway.

About the Author Ian Mitchell

Ian Mitchell is a business analyst and software developer. He's been using UML since before it was UML, and has managed teams of BAs all over the place. He also teaches UML and BPMN, and writes the eaDocX document generator for the Sparx EA tool.

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