zone — the counted aggregation

zone /L3..L10/A name:Aタイプ use:exclusive
zone /site name:敷地 site:1 area:1097.80

zone <path> [attributes...] is an aggregation with no geometry. It groups the spaces beneath it by path prefix, sums their area, and hands attributes down. A dwelling, a department, a site — anything that is counted but has no form of its own — belongs here.

Because a zone has no form, it appears in no plan and no axonometric, and it cannot be an end of a boundary.

The path prefix decides what is beneath

Beneath the zone /L1/A is every space whose path begins /L1/A/. A space at the zone's own path is not beneath it.

grid X 0 3600 7200
grid Y 0 4000
level L1 0 h:2400 slab:150
zone /L1/A name:Aタイプ use:exclusive
space /L1/A/ldk ldk X1..X2 Y1..Y2
space /L1/A/room room X2..X3 Y1..Y2 use:common

$ npx tsx src/cli.ts stats z2.muro
L1
  /L1/A/ldk	ldk	ldk	14.40 m2
  /L1/A/room	room	room	14.40 m2
  Subtotal 28.80 m2
Total 28.80 m2 (indoor floor area)
By zone (counted aggregation):
  /L1/A	Aタイプ	28.80 m2
  ldk: 14.40 m2
  room: 14.40 m2
By use: exclusive 14.40 m2 (50.0%) / common 14.40 m2 (50.0%)

use: is inherited by everything beneath, and a declaration on the space wins. Above, /L1/A/ldk inherits exclusive from the zone while /L1/A/room keeps the common it wrote itself. Where zones nest, the deepest zone is the source of inheritance.

To divide into rooms, make the parent a zone

When splitting a dwelling into rooms, the parent must not be a space. Putting a space with a region beneath a space with a region makes the two regions overlap, which is the error GEO02.

grid X 0 3600 7200
grid Y 0 4000
level L1 0 h:2400 slab:150
space /L1/A unit X1..X3 Y1..Y2
space /L1/A/ldk ldk X1..X2 Y1..Y2

✖ z1.muro:line 4: Space regions overlap: /L1/A and /L1/A/ldk

Rewrite space /L1/A unit X1..X3 Y1..Y2 as zone /L1/A name:Aタイプ and it passes. The dwelling's area is summed from beneath, so it is never written.

The attributes

Five keys may be written on a zone, plus any namespaced key containing a dot. A key in neither category is the error ATT03.

Key	Value	Meaning
name:	free word	Display name, shown in listings and totals
use:	free word	The aggregation axis. Inherited by the spaces beneath; a declaration on the space wins
site:	0 / 1	The mark of the site. The zone with 1 is what site asks about. One per model
area:	positive number, m²	The declared site area (a survey figure). Reconciled against the derived area
uid:	opaque token	Persistent identity across renames. Digits alone, or whitespace, is an error. Unique across the whole model, spanning space and zone

road: belongs to the exterior space that is the road, not to a zone. On a zone it is stopped.

✖ z7.muro:line 4: zone /L1/A carries road:, which is not in the ledger (check the spelling, or add a namespace if the value is only carried — e.g. acme.road:12000)

The site zone

The zone carrying site:1 is the site. Site area, road frontage, building coverage and floor area ratio are all derived starting from it.

koyu 1.0
grid X 0 12000
grid Y 0 10000
level L1 0 h:3000 slab:200
zone /site name:敷地 site:1 area:120.00
space /site/bldg office X1..X2 Y1..Y2 level:L1 name:事務所
space /road exterior road:6000 name:前面道路
boundary /site/bldg /road edge:S t:200
polygon /site 0,0 12000,0 12000,10000 0,10000

$ npx tsx src/cli.ts site site.muro
Site /site (敷地)
  Site shape: polygon with 4 vertices (a polygon declaration — given geometry)
  Site area: declared 120.00 m2 / derived 120.00 m2
  Road: /road (前面道路) width 6000mm / frontage 12000mm
  Building footprint (horizontal projection, rough): 120.00 m2 → building coverage ratio 100.0%
  Total floor area: 120.00 m2 → floor area ratio 100.0%

Three things to read in that.

• area: is a declared survey figure, reconciled against the derived area. A disagreement is reported not by koyu check but by koyu validate as site.area — nothing about the composition is broken; a given and a form disagree, which is an architectural matter.
• The shape of the site is written separately, by polygon. Without a polygon for the site:1 zone, the derived area comes from the union of the spaces on the site and the building's horizontal projection. A polygon with no corresponding zone is the warning SIT04.
• /site is not a level name, so the spaces beneath it inherit no level. Drop the level:L1 above and it becomes the error SUF02.

Level spans

If the first segment of the path has the form L3..L10, it expands over the declared levels in ascending z, exactly as for a space. This is how the same zone is placed on every typical floor.

zone /L3..L10/A name:Aタイプ use:exclusive

Diagnostics

Situation	What comes out
The same zone path declared twice	a parse error (Duplicate zone path: /L1/A)
No space beneath it	ZON01 — warning
A space and a zone at the same path	ZON02 — warning
uid: all digits / containing whitespace / duplicated	UID01 / UID02 / UID03 — errors

$ npx tsx src/cli.ts check z3.muro --json
[
 {
  "code": "ZON01",
  "severity": "warning",
  "message": "There are no spaces beneath zone /L2/A",

ZON01 stays a warning because a file split into layers may legitimately be read before the layer holding its spaces. If it is still empty after composition, the path is almost always misspelled.

Canonical JSON

A zone holds its path and its attributes. Area is derived, so it is not stored.

  "zones": {
    "/site": {
      "attrs": {
        "area": 120,
        "name": "敷地",
        "site": 1
      }
    }
  },