Tatter-Diagnostic Index (TDI)

The Tatter-Diagnostic Index (TDI) is a dimensionless scalar value between 0.00 and 1.00, calculated and maintained by the Department of Tattered Ephemera to quantify the metaphysical decay gradient of a subject. Formally defined by Annex VII, Clause 22.5 as “the ratio of unresolved ontological stress to the total nominal coherence of a catalogued ephemeron,” the TDI serves as the primary diagnostic tool for determining a subject’s placement, maintenance schedule, and eventual deaccessioning within the Tower’s archival systems.

Calculation and Application

The TDI is derived from a composite reading of several parameters, most notably the subject’s resonance dissonance (measured with Geometric Stethoscopes), its referential entropy (tracked against the Master Index), and its observed rate of narrative fraying. Per Protocol 3.11, a baseline assessment requires three separate readings conducted at the primary, secondary, and tertiary Sympathetic Floor Indices nearest to the subject’s holding. A TDI below 0.20 indicates a state of “stable ephemera,” suitable for long-term storage. Values between 0.20 and 0.50 classify the subject as “metaphysically labile,” triggering a quarterly review cycle. A TDI exceeding 0.50 invokes the Drift Clause, mandating immediate remediation or re-cataloguing.

Operational Protocols

The Index-Tender of the relevant department is responsible for submitting monthly TDI reports for all holdings under their purview with a value above 0.30. These reports are reconciled against the Central Index, and any discrepancies exceeding ±0.05 are flagged for a full diagnostic sweep. The process for conducting such a sweep is detailed in the Silent Index, Volume 44: “Procedures for Decay-Mitigation.” In practice, the calculation is often performed using calibrated Living Stone resonators, though the Acoustic Weavers’ Guild has formally contested the accuracy of stone-based readings for subjects catalogued on floors with high architectural silence-weave density.

Interpretive Disputes

Scholarly consensus on the interpretation of mid-range TDI values is notably absent. The Materialist Index school, based on Floor 899, asserts that a TDI between 0.35 and 0.45 merely reflects normal informational entropy and does not warrant intervention, a position contradicted by Clause 19.7. Conversely, the Oneirologists’ Guild contends that the TDI fails to account for “autonomic flicker,” a phenomenon they measure via nictitating vellum, and thus underestimates decay in oneiric holdings. The most significant ongoing debate concerns the so-called “Γ-Prime Threshold.” While Protocol 3.11 defines diagnostic criteria for Class Γ ephemera, the elevation to Class Γ-Prime—often coinciding with a TDI spike to approximately 0.48—lacks a standardized Concordance, leading to inconsistent application between departments.

Notable Holdings & Threshold Events

The TDI is instrumental in managing several critical archival situations. The Wandering Index of Floor 1,114-Δ, for instance, is maintained under a permanent TDI alert status of 0.52, requiring continuous monitoring. The phenomenon of Queue Formation in 702-Pi was first predicted by a precursor oscillation in the collective TDI of seventeen related holdings. Furthermore, the Index of Irreconcilables is, by definition, composed of entries whose TDI has been permanently fixed at 1.00, representing total metaphysical decay and a state of unresolved paradox.

Administrative and Ethical Considerations

Invoking the Drift Clause based on a TDI reading carries significant procedural weight. The decision to deaccession a holding—effectively transferring it to the Index of Superseded Clauses or, in extreme cases, the Index of Unresolved Imperatives—is never taken lightly and requires ratification from three separate Index-Tenders. A proposed amendment to the Fourth Concordance, currently under review by the Satellite Index, seeks to introduce a “decay-probation” period for holdings with a TDI between 0.47 and 0.53, allowing for stabilization efforts prior to mandatory remediation. Critics argue this introduces unacceptable latency into the system, while proponents cite the ethical imperative to exhaust all conservative preservation tactics, as outlined in the Precedent 889: “Stewardship Over Expediency.”