[HTML; ‘good design is invisibile’] Some views on programming, taken in a wide sense and regarded as a human activity, are presented. Accepting that programs will not only have to be designed and produced, but also modified so as to cater for changing demands, it is concluded that the proper, primary aim of programming is, not to produce programs, but to have the programmers build theories of the manner in which the problems at hand are solved by program execution.

[Keywords: human factors, theory, programming psychology, programming methodology]

…The notion of theory employed here is explicitly not confined to what may be called the most general or abstract part of the insight. For example, to have Newton’s theory of mechanics as understood here it is not enough to understand the central laws, such as that force equals mass times acceleration. In addition, as described in more detail by Kuhn1970 (pg87ff), the person having the theory must have an understanding of the manner in which the central laws apply to certain aspects of reality, so as to be able to recognize and apply the theory to other similar aspects. A person having Newton’s theory of mechanics must thus understand how it applies to the motions of pendulums and the planets, and must be able to recognize similar phenomena in the world, so as to be able to employ the mathematically expressed rules of the theory properly.

…Accepting program modifications demanded by changing external circumstances to be an essential part of programming, it is argued that the primary aim of programming is to have the programmers build a theory of the way the matters at hand may be supported by the execution of a program. Such a view leads to a notion of program life that depends on the continued support of the program by programmers having its theory. Further, on this view the notion of a programming method, understood as a set of rules of procedure to be followed by the programmer, is based on invalid assumptions and so has to be rejected. As further consequences of the view, programmers have to be accorded the status of responsible, permanent developers and managers of the activity of which the computer is a part, and their education has to emphasize the exercise of theory building, side by side with the acquisition of knowledge of data processing and notations.

Peter Naur’s classic 1985 essay “Programming as Theory Building” argues that a program is not its source code. A program is a shared mental construct (he uses the word ‘theory’) that lives in the minds of the people who work on it. If you lose the people, you lose the program. The code is merely a written representation of the program, and it’s lossy, so you can’t reconstruct a program from its code.

[from Alistair Cockburn2006] Peter Naur and Pelle Ehn wrote the two most compelling and accurate accounts of software development I have yet seen. Neither is as well known as it needs to be, and Ehn’s book is out of print. I am happy, therefore, to present extracts from their articles, for wider readership. Peter Naur’s “Programming as Theory Building” neatly describes the mental activity of creating software and explains the “metaphor building” activity in Extreme Programming (XP).

…This article is, to my mind, the most accurate account of what goes on in designing and coding a program. I refer to it regularly when discussing how much documentation to create, how to pass along tacit knowledge, and the value of the XP’s metaphor-setting exercise. It also provides a way to examine a methodology’s economic structure.

In the article, which follows, note that the quality of the designing programmer’s work is related to the quality of the match between his theory of the problem and his theory of the solution. Note that the quality of a later programmer’s work is related to the match between his theories and the previous programmer’s theories.

Using Naur’s ideas, the designer’s job is not to pass along “the design” but to pass along “the theories” driving the design. The latter goal is more useful and more appropriate. It also highlights that knowledge of the theory is tacit in the owning, and so passing along the theory requires passing along both explicit and tacit knowledge.

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