Interface Protocols: Using the Displacement Rubric for Cross-Model Alignment

This paper defines a formal interface for applying the Displacement Rubric to independently constructed models in a consistent, reproducible, and methodologically neutral manner. The interface treats the rubric strictly as a measurement system rather than as an interpretive or physical theory. It does not introduce new physical claims, impose structural corrections, or prescribe a preferred ontology. Instead, it provides a disciplined operational procedure through which authors can map their own models onto a shared structural evaluative framework without interpretive imposition. The protocols specify explicit input requirements, alignment steps, and output interpretation rules. Misalignment is treated as diagnostic rather than evaluative: a non-match may reflect structural difference, a translation gap, or insufficiently defined inputs rather than a defect in the model itself. When required structural elements cannot be identified reproducibly, the interface yields ambiguity rather than analyst-supplied completion, thereby preserving author primacy and constraining hidden translation. The mapping procedure requires only structurally identifiable correspondence under the model’s own definitions, not semantic equivalence. The paper also formalizes the limits of the interface by identifying ambiguity conditions and failure modes, including incomplete specification, disputed invariants, analyst disagreement, and representational mismatch. Examples across continuous, discrete, probabilistic, and underspecified models illustrate how the interface produces multidimensional structural classifications rather than scalar rankings. The strongest-available-rival standard is treated as a procedural requirement for disciplined comparison rather than as a claim that all possible rivals have been exhausted. This manual is standalone but designed to operate alongside the companion paper A Discriminator Framework for Structural Cosmology: Support Classes, Failure Modes, and Comparative Evaluation (DOI: 10.5281/zenodo.19562922), which provides the broader comparative context in which alignment results may be interpreted. In typical use, models are first mapped through the interface protocols defined here, after which the resulting structural classifications may be situated within that broader comparative framework. Together, these works establish a reproducible, versioned system for cross-model structural alignment and disciplined comparative evaluation.