Cohesion and Coupling Revisited

Companies have repeatedly demonstrated that branching into multiple areas can have extremely damaging effects on operations. For example, I worked for NIKE when it thought it would be a good idea to expand from athletic shoes to athletic equipment. The two seemed related, but when the business tried to adapt, people found that NIKE did not have the infrastructure to handle the new line of business. Both the new line of business and the existing footwear business took a nosedive. When NIKE dropped back to a focus on footwear only, the business recovered and grew at an unprecedented rate.

Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa. The software quality metrics of coupling and cohesion were invented by Larry Constantine, an original developer of Structured Design who was also an early proponent of these concepts (see also SSADM). Low coupling is often a sign of a well-structured computer system and a good design, and when combined with high cohesion, supports the general goals of high readability and maintainability.