#11 The Missing Implementation Layer in Sustainability Systems – Defining the Sustainability Implementation Infrastructure Layer (SIIL)

This paper defines the Sustainability Implementation Infrastructure Layer (SIIL) as a coordination-layer category within sustainability transition system architecture and introduces a classification framework for identifying ecosystem-scale implementation coordination capacity across institutional environments. Drawing on the full TSSF–SIIL research stack, including cross-sector probes, actor-type topology mapping, responsibility-boundary validation, exclusion synthesis, and prior-art closure verification, the study establishes SIIL as a structurally unassigned implementation-coordination position linking policy frameworks, certification systems, workforce preparation environments, financing structures, and operator-level deployment pathways.