What Remains Consistent? Structural Invariance Index(SII) for Visible-Body Observation v0.1

This exploratory public concept note discusses structural consistency in visible-body observation. It asks what visible structural relationships may remain relatively consistent across changing conditions such as body weight, hydration, posture, training phase, measurement timing, or capture context. The note presents a simple illustrative notation, I_str ≈ Φ_observed / Φ_reference, to describe the conceptual comparison between an observed structural relationship and a selected reference relationship. This notation is purely conceptual and is not a mathematical equation, computational model, scoring formula, diagnostic index, or operational algorithm. No proprietary algorithm, threshold, weighting system, calibration procedure, branch rule, scoring logic, protected interpretation engine, or implementation detail is disclosed. The note is intended solely for scholarly discussion, methodological exploration, and future interdisciplinary refinement. Version:v1.0.2 — Public Concept Note / Working Paper