Doomed To Repeat It

Technologists are particularly susceptible to recency bias. It’s one reason why I try to read older computer science literature from time to time (especially work from the 60s and 70s). The Mythical Man-Month is my canonical example; it should be required reading for everyone who works with technology. The Psychology of Computer Programming contains timeless truths of what it takes to lead a team of software engineers. Donald Knuth’s The Art of Computer Programming is a dense, three volume work, but much treasure lies within. I’ve only finished the first book, but I came away with tremendous respect for the geniuses that paved the way for us fortunate souls who have IDEs, fast compilers, and gigabytes of RAM.

Today I read On the Criteria To Be Used in Decomposing Systems into Modules, a research paper by D.L. Parnas of Carnegie-Mellon University, published in 1972. While the details of the middle section weren’t terribly interesting, it’s the bookends of introduction and conclusion that impressed me. The benefits of two-pizza teams were clearly understood fifty years ago, for example (“separate groups would work on each module with little need for communication”) and the paper lays out a novel approach to decomposition (to me, at least):

“We propose instead that one begins with a list of difficult design decisions or design decisions which are likely to change. Each module is then designed to hide such a decision from the others.”

The above resonates with prior posts I’ve written on abstractions, especially Out of Sight, Out of Mind. If the goal of abstraction is to hide difficult detail, we ought to modularize with that goal front-and-center.