Smalltalk: Conceptual Integrity in Action.

O ne of the most eye-opening and influential ideas in my journey as a programmer was the concept of conceptual integrity, introduced by Fred Brooks in The Mythical Man-Month in his essay Aristocracy, Democracy, and System Design.

“It is better to have a system omit certain anomalous features and improvements, but to reflect one set of design ideas, than to have one that contains many good but independent and uncoordinated ideas”

In a nutshell, conceptual integrity consists of a set of well-related, composable concepts and the relationships between them, forming a kind of conceptual algebra.

When we introduce a new concept that doesn’t integrate well with the others, the conceptual algebra suffers in the form of increased complexity. Special or exceptional cases must be considered, which limits the expressiveness of the algebra and raises the cognitive load for those who have to play with it. Just one poorly selected concept affects the whole.

In a way, what Brooks is suggesting is that design lives in the constraints we impose on the material we work with. This is especially true in software development.

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