Status: OUT
Abstract coupling and object composition form the dual foundation of GoF pattern flexibility: abstract coupling provides the substitutability mechanism (references to abstract types rather than concrete ones) while composition provides the assembly mechanism (delegating to composed objects at run-time) — and behavioral patterns systematically exploit both.
Three depth-1 conclusions converge on a single insight — abstract coupling and composition are complementary, not redundant
Depends on (SL): abstract-coupling-enables-pattern-flexibility, behavioral-patterns-favor-composition, composition-superiority-for-reuse