Tatter-Diagnostic Index

The Tatter-Diagnostic Index (TDI) is a dimensionless scalar value between 0.00 and 1.00, formally defined in the Third Concordance as the ratio of unresolved ontological stress to the total nominal coherence of a catalogued ephemeron. It serves as the primary quantitative measure of metaphysical decay gradients and is the cornerstone of assessment protocols within the Department of Tattered Ephemera. A finalized TDI score is the mandatory output of any Tatter Assessment and is directly incorporated into higher-order stability metrics, including the Stress-Fracture Index.

Formal Definition and Calculation

The Third Concordance, Clause 14.7, provides the canonical formula: TDI = Σ(Su) / Cn, where Σ(Su) is the sum of all unresolved ontological stress vectors acting upon the subject, and Cn is its total nominal coherence as logged at the moment of initial accession. The measurement is typically expressed to two decimal places. Calculation requires specialized instrumentation, most commonly a calibrated Auscultatory Engine paired with Geometric Stethoscopes to isolate stress signatures from ambient background noise. The resulting data is processed through a Resonance Comparator Array to derive the final scalar.

Interpretation Scale

The Department of Tattered Ephemera maintains the official interpretative framework for TDI values, as outlined in Annex Δ of the Department's procedural manuals.

• 0.00 – 0.19 (Stable): Subject exhibits negligible decay gradient. Ephemeral binding is considered permanent for archival purposes.
• 0.20 – 0.49 (Attenuated): Mild ontological stress detected. Subject requires bi-annual re-assessment and may be subject to stabilization protocols.
• 0.50 – 0.74 (Frayed): Significant metaphysical decay is present. The subject is at risk of developing Reality Shear and must be quarantined from cohesive holdings. Monthly monitoring is mandated.
• 0.75 – 0.89 (Tattered): Severe decay gradient. Subject integrity is compromised, and it may begin to influence adjacent catalogued items. Placement in a Class Γ containment sector is typically required.
• 0.90 – 1.00 (Critical): The subject's nominal coherence is almost entirely subsumed by unresolved stress. Immediate de-accession and metaphysical scrubbing procedures are initiated to prevent cascade failures.

Integration with Structural Diagnostics

The TDI is not used in isolation. Per Bureau of Structural Integrity Directive 88, the TDI maps directly to a Unitary Stability Coefficient (USC) for integration into the broader Stress-Fracture Index. This allows structural engineers to correlate ephemeral decay with physical manifestations such as Granular Fracture in shelf-load-bearing walls. Furthermore, TDI trending data is a key input for the Diagnostic Catalogue, helping to predict and classify emergent forms of metaphysical wear.

Indexing and Cross-Referencing

Every finalized TDI score is logged in the Central Index Column under the originating subject's accession number. Satellite indices, such as the Sub-Index of Unfulfilled Prophecies, maintain specialized cross-references that tag entries with their current TDI, allowing for rapid retrieval of all holdings within a specific decay band. The Index-Tender of a floor is responsible for ensuring these updates propagate correctly according to the Index Column Protocol. Discrepancies between the Central Column and a local Silent Index often serve as the first indicator of a measurement error or an actively deteriorating subject.

Scholarly Disputes and Anomalies

While the TDI's utility is undisputed, its theoretical underpinnings are contested. A persistent school of thought, based on a contested reading of the First Concordance's provisions on substantivity, argues that the "nominal coherence" (Cn) is not a fixed value but degrades asymptotically, rendering the TDI ratio inherently unstable over long timescales. This has led to the practice of "baseline re-anchoring" in some departments, a procedure not sanctioned by the central Department.

Notable anomalies include the so-called "Reverse-Tatter" effect, documented in seventeen instances where a subject's TDI has been observed to decrease without intervention, and the "Shear-Stasis" paradox, where a TDI reading above 0.90 remains constant for centuries without triggering expected collapse. These cases are preserved in the Diagnostic Catalogue under review sigils.

Procedural Mandates

The application of the TDI governs several key archival workflows. No ephemeron may be transferred between floors without a TDI assessment conducted within the previous standard quarter. Any holding with a TDI exceeding 0.70 automatically triggers a review of the Sympathetic Floor Index for potentially correlated instabilities. Furthermore, the Standard Topographical Index uses TDI heat-maps to guide maintenance crews away from areas of high metaphysical fatigue, routing them through corridors indexed as structurally inert.