Even More Aphorisms

Alan Perlis was the first winner of the Turing Award in 1966. In 1982 he published [1] a set of 130 epigrams on programming. His aim, he explained, was to capture—in metaphors—something of the relationship between classical human endeavours and software development work. "Epigrams," he wrote, "are interfaces across which appreciation and insight flow." This post offers a few aphorisms. My dictionary tells me that an epigram is 'a pointed or antithetical saying', while an aphorism is 'a short pithy maxim'. Whatever they may be called, I hope that these remarks will evoke some appreciation and insight.

41. Causality is not a topic in logic or science: it is an informal notion indispensable in modelling and in failure diagnosis.
42. A wise development project prefigures the system's evolution by enacting its earliest phases in vitro.
43. The 'fault' concept is minimally useful in modelling—if it's in the model it's not a fault. The vital idea is deviation between model and subject.
44. Modelling the physical world without domains is destructive fragmentation: it deprives causal links of their local habitation.
45. Any formalism restricts what you can say: as evidence of its own applicability it is merely a self-fulfilling prophecy.
46. Separation of concerns is the mother of simplicity; but giving birth is not always easy.
47. Natural language is the indispensable intermediary between unfettered thought and formalisation.
48. The machine-world interface of sensors and actuators gives the machine a wafer-thin view of the governed world.
49. The Eight Queens problem is not about chess; but the Lift problem really is about lifts.
50. An unsuitable method, like a chisel used as a screwdriver, works poorly, breaks easily, and is hard to use.

[1] A J Perlis; Epigrams on Programming; ACM SIGPLAN Notices 17,9 September 1982.

Links to other posts:
 ↑  Causality: Causality explains how a system works
 ↑  Physical Bipartite System: The nature of a bipartite system
 ↑  Simplicity: Simplicity is hard, but vital
 ↑  Triplet Models: What models are needed of the machine and governed world?
 ←  Ten Aphorisms: Ten short remarks
 ←  Ten More Aphorisms: Ten more short remarks
 ←  Yet More Aphorisms: Ten more short remarks
 ←  Again More Aphorisms: Ten more short remarks