Interface Structure as Admissibility and Composition Constraints - A Level-Dependent Framework for Relational Physical Theories

This preprint develops a level-dependent interpretation of admissibility and compositional constraints within relational physical frameworks. Building on prior work establishing that local relational assignments together with accessibility structure are generally insufficient to determine unique cross-context composition outcomes, the paper examines how additional compositional constraints may be interpreted operationally across different descriptive levels. Rather than introducing new dynamical entities or modifying established physical theories, the framework treats admissibility and compositional constraints as structural conditions governing how relational information may be propagated, filtered, translated, and consistently composed across multiple interaction contexts. The work situates this interpretation relative to relational quantum mechanics, decoherence-based descriptions, gauge-theoretic transition structure, quantum information theory, relativistic causal structure, and distributed systems frameworks. Representative physical constraint classes discussed include causality, consistency, stability, equivalence preservation, and information-theoretic limitations. The framework is intentionally structural, interpretive, and ontology-neutral in scope. Its primary contribution is to clarify the role of admissibility and compositional constraints in maintaining compositionally consistent relational descriptions across distributed interaction contexts.