4. How formal do we really have to be?

I'd make a small wager that, by now, you're feeling somewhat punch-drunk...  this is not the easiest of things to grasp and get your head around...  particularly now we've 12 boxlettes!

So what's the essence of all this?  How "accurate" and "precise" do you really need to be?  Well, if this was some form of safety critical system such as a motorway's roadside information system or maybe a bank's business rests on "getting it right", then probably the model and its views have to be as formal as possible:  you don't design and then build a new model of car or a motorway's bridge without proper blueprints.

But there's also plenty of room for informality - sketching ideas for discussion and clarification, often for use with those who are not professional system designers.  These sketches cannot be accurate representations of the model in the box (the lay person would not understand them), but they can convey the essence of its design, enabling design options to be discussed in terms of what the system will then be able to do (or not do), without alienating those you're trying to work with.

But I ask one thing of you.

Please, please, please try to hold onto the viewpoint from which you are creating this sketch.  So often, the moment we abandon "proper modelling" we also abandon the notion of viewpoints.  Please don't - for example:  

• If you are discussing the structure of an application, sketch from the "logical/application/functional" viewpoint - don't confuse matters with additional issues of data distribution (technical/operational) or software product packaging (physical/application).
• If you are discussing the performance or security implications of storing business information locally on a laptop, compared to centrally and requiring connectivity to get at it, make sure your sketch from the "logical/technical/operational" viewpoint - does it even need to refer to the application at all?

This challenge is not helped at all by the fact that, so often, the standard work products we have available for such sketching (might it, perchance, be called the "Solution Design Overview Diagram"?) make no reference whatsoever to the purpose of the sketch, other than "free-format communication"...