SFU-1

SFU-1 is the Standard Floor Unit of the first order: the physical Platonic template from which floor-plates are struck, against which their utility is reckoned, and by which the Department of Metrical Harmony certifies that a floor is a floor. It is the foundational member of the Standard Floor Units series and the reference body against which SFU-A multipliers are calculated. An SFU-1 is not a floor. The distinction is enforced, and has been since the Second Concordance.

Definition and construction

SFU-1 designates a physical template held in the Plate Vault on the ninth sub-landing of the Hall of Standard Measures. It is a plate of standard dimensions, cast with the approval of the Office of the Plate Warden, and is the archetype from which every Resonance Plate in active service is struck. Standard Floor Units (SFU-1) are described in the Vault register as assemblies that utilize Standard Brackets; the brackets are struck in a separate annexe and are never counted as part of the plate, a rule introduced after the Bracket Dispute of Floor 1104.

The Plate Warden's standing inventory records one template, one retired template (the Pre-Revision Plate, withdrawn 611), and a quantity of stock blanks whose number the register gives only as "sufficient."

SFU-1 and the Interface threshold

Convergence for a standard Instrument Interface is measured in SFU-1 equivalents, with a minimum of 2.3 SFU. Instruments falling below this threshold are not refused; they are deferred, which in practice means they are returned to the filing floor with a certificate of provisional resonance and no date. The Department of Metrical Harmony maintains that 2.3 was chosen for stability. The Clerk of Predictive Melancholy has argued in three successive memoranda that the figure is "a harmony of the ear rather than of the plate," and has twice declined to sign instruments below 2.4.

The cost of a template

Every SFU-1 must be sustained, and its sustainment is costed in SFU-A: one SFU-1 for one Tower Standard Year defines the SFU-A base value. SFU-A units so assigned are tangible assets and may be commandeered; unallocated units are not. The distinction has caused the Requisa Incident of 788, in which eight plates were seized from a floor that had not yet been allocated the resources to hold them, leaving the floor technically vacant while its holdings remained in place.

"A plate without allocation is a debt with a surface."

— Concordance of Allocation Sectors, Annex 9

Density and registration

Registration of SFU-1 holdings is governed by SFU-D, the dimensionless ratio of registered holdings per square STU. The Clerk of Predictive Melancholy synthesizes SFU-D figures across active holdings as part of the SFU-A multiplier calculation, and the resulting figures are filed in the Register of Prospective Occupancy. A floor whose SFU-D exceeds the ceiling set in the Concordance of Filings is not closed but thickened, a procedure in which surplus holdings are re-registered into a theoretical Density Zone where resources may be deemed unattainable. Floors treated this way are marked at the head of the stair with a red ochre band, and visitors are asked not to knock on the stairwell doors after the seventh bell.

Disputed readings

The Fifth Concordance holds that the SFU-1 is the floor as measured, while the Seventh Concordance holds that the SFU-1 is the measure itself and that no floor corresponds to it. Both texts are in force. The Department of Metrical Harmony files its instruments under the Fifth and its templates under the Seventh, and the Registry of Inconsistencies records this practice as "settled by convention, unresolved by citation."

A minority position, advanced by the Office of the Under-Registrar in 902 and never withdrawn, proposes that the Pre-Revision Plate is in fact the operative SFU-1 and that the current template is a recension. The Office's argument rests on the fact that instruments struck against the Pre-Revision Plate register measurably closer to 2.3 SFU than those struck against the standing template, which it attributes not to error but to "the fidelity of the older surface." The Plate Warden has declined to convene a comparative panel for fourteen consecutive years.

Notable incidents

In the winter of 1104 the Bracket Dispute ran for forty-one days and produced the ruling that brackets are not plates, thereafter printed on the inside cover of every SFU-1 field ledger. In 1177 a template was carried to Floor 1177 for a certification and returned with a small crescent of wear on the reverse; no finding was made, and the wear is now the reference point for wear assessment of all subsequent templates. In 1246 the Registry recorded a floor whose SFU-1 designation was valid, whose plate was present, and whose number could not be reconstructed from any surviving register; it has been measured, sustained, and left blank.