This title is certainly provocative. We all know that this claim corresponds to something that is impossible. No! We cannot construct faultless systems; just have a look around. If it were possible, it would have been already done a long time ago. And anyway, to begin with, what is a “fault”?

So, how can we imagine the contrary? We might think: yet another guru trying to sell us his latest universal panacea. Dear reader, be reassured, this Prologue does not contain any new bright solutions and, moreover, it is not technical; you'll have no complicated concepts to swallow. The intention is just to remind you of a few simple facts and ideas that you might use if you wish to do so.

The idea is to play the role of someone who is faced with a terrible situation (yes, the situation of computerized system development is not far from being terrible – as a measure, just consider the money thrown out of the window when systems fail). Faced with a terrible situation, we might decide to change things in a brutal way; it never works. Another approach is to gradually introduce some simple features that together will eventually result in a global improvement of the situation. The latter is the philosophy we will use here.