This is a blog about modelling.

More specifically, it’s about Visual modelling, that is, expressing abstractions of the world via diagrams.

So how we draw those diagrams – what we choose to put in them, what we try to say with them, is critical. So this article is going to serve as a starting point for ideas on:

  • Why some diagrams are better than others. This is really just a chance to show some of my personal favorites, and say why I think they are successful.
  • What to include in diagrams, to help us create better models. How to avoid visual- and meaning-overload
  • How to present diagrams, so people can read them. Some diagrams may just show our working-out, and are not for public consumption. Others are going to be our shop-window, our main deliverable. So presentation matters.
  • How big, or small, to make them. Size is important.

I’m sure that there is lots of psychology and information theory which has answers to all these questions, but these are some ideas from a modelling practitioner: if you know better, then please say so.

Why some diagrams are better than others

A great diagram speaks to us.

It tells us something, or better yet, allows us to discover something for ourselves, perhaps even something beyond what the author knew themselves. I generally start my courses on modelling with some good, and bad, examples, of model diagrams but my clear favorite is the Harry Beck London tube map.

Another, more recent example, was sent to me me by my daughter, and XKCD fan, and is a wonderfully informative and elegant infographic about radiation. When you next see an article on the TV about the terrible dangers of radiation, consult this diagram.

And the final one – for the moment – is the one which I treasure more than all others, as it’s the one which made me decide that modelling was a worthwhile human activity: the GoF ‘Composite’ Pattern:

composite

This is so simple: 3 boxes and 3 lines, but it conveys a concise solution to all kinds of problems. The first time a saw this (and had it explained to me, slowly) was a magical moment. Models can be simple, small, and still be wonderful.

So this is the target for what follows – how should we create diagrams which are simple, easy to read and understand, and which contain useful information and insights.

See also:

  • What to include in diagrams – ideas and content
  • How to present diagrams – presenting that content
  • Size – use and abuse.

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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