Measuring Complexity at the Requirements Stage: Spectral Metrics as Development Effort Predictors

TL;DR

This paper introduces spectral network metrics derived from requirements specifications to predict integration effort, demonstrating high correlation and bridging a gap between complexity analysis and requirements engineering.

Contribution

It applies spectral measures to textual requirements, showing they predict effort better than simpler metrics, and connects structural complexity analysis with requirements engineering practice.

Findings

Spectral measures predict integration effort with correlations over 0.95.

Structural metrics achieve correlations above 0.89.

Density-based metrics show no significant predictive validity.

Abstract

Complexity in engineered systems presents one of the most persistent challenges in modern development since it is driving cost overruns, schedule delays, and outright project failures. Yet while architectural complexity has been studied, the structural complexity embedded within requirements specifications remains poorly understood and inadequately quantified. This gap is consequential: requirements fundamentally drive system design, and complexity introduced at this stage propagates through architecture, implementation, and integration. To address this gap, we build on Natural Language Processing methods that extract structural networks from textual requirements. Using these extracted structures, we conduct a controlled experiment employing molecular integration tasks as structurally isomorphic proxies for requirements integration -- leveraging the topological equivalence between molecular graphs and requirement networks while eliminating confounding factors such as domain expertise and semantic ambiguity. Our results demonstrate that spectral measures predict integration effort with correlations exceeding 0.95, while structural metrics achieve correlations above 0.89. Notably, density-based metrics show no significant predictive validity. These findings indicate that eigenvalue-derived measures capture cognitive and effort dimensions that simpler connectivity metrics cannot. As a result, this research bridges a critical methodological gap between architectural complexity analysis and requirements engineering practice, providing a validated foundation for applying these metrics to requirements engineering, where similar structural complexity patterns may predict integration effort.