In this book I intend to examine the logic and methodology of design from the perspective of computer science. Computers provide the context in two ways. Firstly, I shall be discussing the structure of design processes whereby computer systems are, or can be, designed. Secondly, there is the question of the role that computers can play in the design of artifacts in general – including other computer systems.

The aim of any systematic enquiry into a phenomenon is to uncover some intelligible structure or pattern underlying the phenomenon. It is precisely such patterns that we call theories. A theory that claims to explain must exhibit two vital properties. It must be simpler – in some well defined sense – than the phenomenon it purports to explain; and it must be consistent with whatever else we know or believe to be true about the universe in which the phenomenon is observed.

The phenomenon of interest in this book is such that it cannot be adequately described by a single sentence. That itself is an indicator of its inherent complexity – and therefore of its intrinsic interest.