Programming as Theory Building

Peter Naur argued that programming is mainly the programmers building up a theory of the matters at hand: how the program maps onto the world it serves, why each part is the way it is, and how a new demand fits into it. That knowledge stays with the people, "any documentation being an auxiliary, secondary product." In one case he describes, a second group extending a compiler had full documentation, annotated program texts, written design discussion and personal advice from the original authors, and still proposed patches that "effectively destroyed its power and simplicity"; the original group spotted them instantly. About ten years later, after others had changed it without that guidance, the original structure was "still visible, but made entirely ineffective by amorphous additions of many different kinds." Naur's conclusion: "The death of a program happens when the programmer team possessing its theory is dissolved," and rebuilding the theory merely from the documentation is "strictly impossible." Code accepted from a generator that nobody on the team has reasoned through is likely to start out in that state.

Fake the Rational Design: Parnas and Clements argue for writing the design down as if it had been derived rationally and keeping that record current with every change, so new programmers do not have to depend completely on the old staff; where people move on often, a maintained record is a safer bet than counting on who stays.