Complexity and Coupling: A Functional Domain Approach

TL;DR

This paper defines complexity and coupling within the functional domain of industrial control systems, clarifying their distinctions and impacts on system design to improve understanding and management.

Contribution

It provides a precise, scientific definition of complexity and coupling in the functional domain, highlighting their roles in system design and reducing ambiguity in their application.

Findings

Coupling occurs in the functional domain, not the physical domain.

Complexity is not directly related to system size or component count.

Coupled design increases complexity, which can be mitigated.

Abstract

This paper provides a precise and scientific definition of complexity and coupling, grounded in the functional domain, particularly within industrial control and automation systems (iCAS). We highlight the widespread ambiguity in defining complexity and coupling, emphasizing that many existing definitions rooted in physical attributes lead to confusion and inconsistencies. Furthermore, we re-exhibit why coupled design inherently increases complexity and how potentially this complexity could be reduced. Drawing on examples from various disciplines, such as software engineering, industrial automation, and mechanical design, we demonstrate that complexity does not necessarily correlate with system size or the number of components, and coupling, unlike common belief in software engineering, actually does not occur in the physical domain but in the functional domain. We conclude that effective design necessitates addressing coupling and complexity within the functional domain.