Impact Assessment

Impact Assessment is the collective designation for the family of evaluative procedures by which the Tower determines what a proposed act, text, structure, or omission will do to the archive around it before permitting that thing to be done. It is not a single instrument. The catalogue distinguishes eleven named assessments bearing the word, of which six are in active use, three are suspended pending reconciliation of conflicting Concordances, and two are retained only because no Librarian has been found willing to sign the instrument that would abolish them. Common usage treats "Impact Assessment" as a generic term; the Office of Preliminary Assessment has twice ruled that it is not generic and should be capitalised, and has twice been overruled.

Origin and the Cascade of 1147

The practice descends from the Tripartite Assessment, whose three limbs — Ontological Coherence, Environmental Impact, and Conceptual Appetite — were for two centuries the whole of the Tower's evaluative apparatus. The multiplication of separate assessments began after the Cascade of Floor 604, a referential failure in which a single amended definition propagated through four thousand citations in the course of an afternoon and left the western stacks describing a category of object that had never been catalogued. The inquiry that followed found no instrument specifically charged with measuring what one text does to another.

Ordinance 1147-A supplied the omission. Its Stage 3, the Ontological Impact Assessment, mandated a formal estimate of collateral reference prior to any amendment of the referential order. Within forty years the Referential Impact Assessment (RIA) had displaced Stage 3 in ordinary practice, and within ninety the RIA itself had acquired four annexes and a rival in the Retroactive Drift Assessment. Clerks of the period referred to the sequence as "the ladder," though nothing in 1147-A uses the word and the First Recension of the ordinance contains no stages at all.

The named assessments

Contemporary usage recognises the following, each with its own form, seal, and office of deposit. The list is drawn from the schedule annexed to Circular 88/2 and is not exhaustive; three further assessments are known from fragments but cannot now be reconstructed sufficiently to be filed.

• Referential Impact Assessment (RIA) — citation chains, upstream and downstream.
• Ontological Friction Assessment — resistance offered by established categories to a new entry.
• Hypothetical Durability Assessment — the survival of an uncatalogued idea if left unrecorded.
• Retroactive Drift Assessment — alteration of holdings already written.
• Volumetric Impact Assessment — spatial displacement; conducted by the Office of Volumetric Assessment.
• Bounding Impact Assessment — required of all petitions to the Curia of Shifting Context.

Two further instruments borrow the name without belonging to the family strictly defined. The Density Impact Assessment (Form A-77D) governs procurement above 500 Standard Tower Units and is filed with the quartermaster rather than the registry. The Fade Assessment, though concerned with the erosion of marginal entries, is administered by the Bureau of Ontological Placement and is counted here only by courtesy.

The Floor 604 precedent and the Gresham objection

The authority of any Impact Assessment rests on the Floor 604 Precedent, which held that an assessment is binding not on the act it describes but on the office that commissioned it, and that an office may not commission a second assessment of the same act until the first has been formally contradicted. The ruling was intended to prevent duplicate evaluation. It has had the effect of making contradiction the ordinary means of revision.

Objection to this arrangement is associated with the Gresham Scale, which ranks assessments by the cost of contradicting them rather than by their accuracy. On the Gresham account, an assessment cheap to contradict will be contradicted often and is therefore worthless, while an assessment expensive to contradict is never contradicted and is therefore untested. Librarian Ostrev Halden put the matter more briefly in his marginalia to the Floor 604 file: "We do not measure the impact. We measure the expense of saying it did not happen." The Gresham Scale has never been adopted and is cited constantly.

"Where two assessments of equal seal conflict, the later governs. Where the seals differ, the elder governs. Where the seals are equal and the dates are equal, the matter is referred to the Curia, which will not hear it."

— Fourth Concordance, Annex 11, clause 6

Dispute concerning the standard of proof

The principal scholarly disagreement turns on whether an Impact Assessment estimates or determines. The Second Concordance (Annex 3) holds that an assessment is estimative — a projection, revisable on evidence, of consequences that exist independently of it. The Seventh Concordance (Annex 1, clause 2) holds that the consequences of a catalogued act are those the assessment records, and that an act assessed as harmless is harmless because it was so assessed. Both annexes are in force. The Office of Preliminary Assessment applies the Second in the morning and the Seventh after the fourth bell, on the reasoning that the Seventh requires a more settled light.

The practical consequence is that a proposer may obtain either result by choosing an hour, and that the registry's afternoon docket is four times the length of its morning one. Vector Beta, a procedure devised to convert estimative findings into determinative ones by re-referral, is an attempt to bridge the two readings and has generated a further dispute of its own as to whether a re-referred assessment is a new assessment or the same one contradicted.

The Steward's grievance

In the winter of the year recorded as 3 after the Cascade, the steward of the eastern spiral submitted a Phase 3: Initial Assessment for the repair of a stair, anticipating a duration of nine days and no referential consequence. The assessment was returned unopened on the ground that stair repair falls under non-emergency Quiet-Mason work and requires Form Φ-7, not a Phase 3. The steward resubmitted as Φ-7 and was informed that any work on a Quiet Floor also requires the Architects' Guild to assess structural impact, which the Guild would not do without a Phase 3. The stair was not repaired. It remains unrepaired. The file is retained in the eastern registry as a standing example, and the steward's covering note — "The stair does not require an assessment. It requires a stair." — is quoted in the training of every new clerk in the office.

See also Manual of Acoustic Assessment, The Rite of Silent Assessment, and Phase III, which is unrelated.