Stable abstractions principle
Alternative name for Instability and abstractness.
The stable abstractions principle, formulated by Robert Martin, says that a package's level of abstraction should suit its dependency stability. AtlasArc does not infer freedom to change from low Fan-in alone. Instability uses both incoming and outgoing coupling: I = Ce / (Ca + Ce), and it is unavailable for an isolated package. Abstractness and Instability are the inputs; Distance, D = |A + I - 1|, is the separate signal for proximity to the main-sequence balance. These values guide inspection, but the package's intended role determines whether its position is appropriate.