The Datum Interface: The Structural Observer Layer in the Paton System

This paper clarifies the role of the Datum Interface within the Paton System framework. The concept describes the structural observation position from which system states are evaluated relative to their governing constraints. Within the tiered architecture of the Paton System, the datum corresponds to Tier-4 and functions as the layer through which admissibility conditions are assessed before continuation is permitted. Across many scientific and engineering disciplines, systems are implicitly evaluated relative to a structural reference position. Physics employs frames of reference, control theory uses state spaces, optimisation relies on feasibility regions, and biology evaluates viability conditions. Although the terminology differs, each field performs a structurally similar evaluation of system states relative to governing constraints. By identifying the Datum Interface explicitly, the Paton System provides a minimal structural description of the observation layer required for admissibility evaluation across domains. The framework does not modify existing theories or introduce new physical laws. Instead, it clarifies the structural position from which persistence conditions are evaluated within complex systems. This paper therefore functions as a foundational clarification within the Paton System architecture, situating the datum as the interface between the Tier-3 admissibility gate and higher-tier domain interpretations.