Quantifying Symbiosis in Urban Boundary Spaces: An S-Q-B Framework and Co-Symbiosis Index (CSI) for Evaluating Renewal Effectiveness

Abstract

Urban boundary renewal embodies the multi-layered interaction between physical form, environmental experience, and social behavior. Drawing on Symbiosis Theory, this study develops an analytical framework that integrates Structural Potential (S), Interface Quality (Q), and Behavioral Vitality (B) into a unified Co-Symbiosis Index (CSI). The framework quantitatively evaluates how spatial transformation can stimulate social activation and sustainable community vitality.Two renewal cases—Huafu Community and Jingshi Shuju Green Space—are analyzed to verify the model’s applicability. The results show that spatial openness and interface design significantly influence behavioral feedback, while the coupling degree among S, Q, and B determines the overall co-symbiosis performance. The study not only validates the theoretical link between urban morphology and symbiotic dynamics but also provides a practical tool for diagnosing spatial–social coordination in boundary renewal.