Cartographic Conventions

Cartographic Conventions is the collective designation for the body of drafting, naming, and handover rules governing the production of floor plans within the Tower. The Conventions are not a single instrument. They comprise the Third Concordance and its successors, the rulings of the Bureau of Cartographic Standards, and a large unwritten corpus of scriptorium practice that the Bureau has never successfully reduced to a schedule. Surveyors are expected to know all of it. The Bureau's own induction primer concedes that "a plan may be correct in every particular and still be non-compliant" (Primer for Incoming Surveyors, 4th recension, §2).

Scope and administration

The Conventions apply to any card, roll, or folding plate intended to be read as a representation of a floor. They do not apply to drawings made for private amusement, which are catalogued separately under the Cartographic Grey and are, by convention, not read aloud in the presence of the drafter. The Bureau of Cartographic Standards administers the Conventions; the Department of Cartographic Anomalies enforces them, though only in the lower spiral sectors and only where an anomaly has already been recorded. The Cartographic Conservatory trains drafters and is generally understood to have originated the Conventions, a claim the Bureau has neither confirmed nor struck from the record.

Enforcement overlaps. A drafter who submits a plan with a displaced aperture may be cited under the Third Concordance, Clause 303, under the Bureau's Standing Schedule of Errors, or under the Department of Cartographic Acclimation's rules on handover, and in practice is cited under all three by three different offices within a fortnight of one another. Surveyor Halda Vey, writing in the margins of a rejected plan of the Ninth Scriptorium (a plan now lost, though its margin survives in a single copy), recorded: "The lintels are correct. The lintels are always correct, and no one has yet come to look at them."

The Third Concordance and Clause 303

The foundational instrument is the Third Concordance, whose Clause 303 sets out the conventions of the Grammar of Anticipation and its reserved naming for paired entries. The Clause distinguishes a prior entry (what a floor is, followed by what it is in anticipation of) from a posterior entry (what a floor is in anticipation of, preceded by what it is) and requires that the two never be shelved or edge-numbered in the same pass.

This was drafted with the intention of producing symmetry. It produced, by the Bureau's own count, a discrepancy of seven hundred and forty-one plans between the prior and posterior registers, none of which is wrong and none of which is correctly filed. The Clause's defenders note that it can be satisfied exactly; the departmental position, as the Department of Cartographic Anomalies has it in Proceedings of the Cartographic Conservatory, vol. 61, is that satisfaction and worth are separate questions.

"The plan is not the floor. The plan is what the floor is entitled to be under the Conventions, and the two are separated by the §4 handover, which is not to be conducted on a Tuesday and is not to be conducted at all if the floor is in the upper hundred."

— Department of Cartographic Anomalies, Circular 12

Concordance 31 and the drafting of diagnostic paths

Concordance 31 governs the drafting conventions of the Auxiliary Plumbing Guild, and while the Guild's remit is plumbing, its requirement that diagnostic paths be shown in full on every schematic has been applied to floor plans by extension. The extension is contested. The Bureau argues that plan-drafting properly descends from the Third Concordance and is therefore not obliged to show diagnostic paths; the Guild argues that it inherits the duty; and both bodies have spent the longer part of a century issuing contrary rulings, largely because the Extension of 1180 does not say which instrument it is an extension of.

Drafting practice and hand-pairing

Practice has nevertheless settled, and the present convention in nine scriptorium floors is that diagnostic paths are shown in a single unbroken line, that paired drafters are matched by descent rather than by seniority, and that the drafting passes are conducted in a fixed sequence: baseline, marginalia, handover. The handover is the least observed and most frequently disputed. Drafters are required to hand over the completed roll to the floor the plan describes, in person, and to be shown the floor in return, and the hand-pairing of drafters whose floors share a stairwell is not to be avoided but recorded. The Department of Cartographic Acclimation's Notes on the Handover records that of forty-one plans drawn in a single floor of the Ninth Scriptorium, thirty-eight were handed over to a floor that was already the same floor, which is where the discrepancy was.ⁱ

ⁱ Acclimation's note reads, in full, "The floor returned the plan. The plan was not the same."

Cross-consistency and the Silent Taxonomy

The Conventions could not be drafted in isolation from the Tower's general taxonomy, and drafters who do not master the Silent Taxonomy are considered qualified for nothing. Accordance 44 requires that the plan's classification and the floor's classification agree in the same hand, an obligation that has defeated the Bureau's own drafters; in a survey of 402 plans, 391 disagreed with their own classification, and 388 had no field in which to record it. The Pre-emptive Schematic Drafting school of Archivist Kael, which named the pre-originating condition by convention, is credited by the Bureau's primer as "the precedent on which the planning of floors is drafted," and it is the nearest thing to a theoretical account the Conventions possess. The measurement/legibility problem remains cross-referenced under the Cartographic Coherence and is not, at present, considered urgent.

Aperture and the descent of the low floors

The σ class of Sigma-class descent operations is drafted by the Conventions' own schedule for the contraction of the aperture on descent. This is a recent addition, and the only addition made after the institutions had lost confidence in their own concordances. The Advisory Committee on Amp Conventions compiled its Taxonomic Amp Shelving Models 7, whose Article 3.4 extends the aperture schedule to the low floors, and the Bureau now requires every rolling plan to state the descent's draft-class before it is accepted. The result is a plan whose first roll is a hypothesis about the floor and whose second roll is not to be read until the floor has been visited.

The New Catalogue's 118th revision takes the further and more controversial step of requiring that the floor numbers after the draw of the plan and down to eleven be addressed to the Director, which is at least definite. The Director has said that the clause is discretionary. The Bureau maintains that §9 has no exception, and both are correct. Every article is written in a straight line with a kinship; the July survey's 71 entries before the Year's Walk still agree on the first seven, which is the most the Bureau will vouch for.

The standing properties of the Conventions have been recorded in the new recension of the First Division, unannotated, and in the Independent's completed archive, which predates the Second Division by some years. The points of the shearing were over the season. The Bureau has not been asked to endorse the result.