In this period, researchers emphasized capturing the web of interdependencies within engineered and natural systems. Methodologies coalesced around mapping component couplings, probabilistic risk framing, and multiple descriptive languages that together enabled modular design, robust analysis, and adaptive experimentation in complex environments. These strands converged to shape early system architecture practices and cross-domain modeling. Historical Significance: The period reframed complexity as a property that emerges from interactions and description, rather than fixed traits of a system. Foundational ideas included structural matrix representations for design processes, representation-sensitive risk assessment, and multi-modal descriptions that anticipate later complexity science and adaptive systems research. The legacy is a multidisciplinary toolkit for analyzing interdependencies, informing safer design, resilient engineering, and scalable architectures.