area — an uncounted subdivision inside a space

space /L1/hall hall X1..X2 Y1..Y2 name:エントランスホール floor:オーク
  area X1..X1+1800 Y1..Y2 name:土間 floor:モルタル

area <region> [attributes...] is written indented directly under a space and is an uncounted subdivision. A change of floor finish inside a room, the extent of an entrance slab, a fixed furniture zone — anything that holds an extent without dividing the room — belongs here.

The isolation rule — it affects nothing

An area is not a room. It appears in no area total, no room count and no graph.

• Gross floor area comes from the parent space's region. No number of area lines raises or lowers it.
• Adjacency and passage belong to the parent space. An area cannot carry a boundary, and no door or window can be placed on one.
• It appears in neither the zone totals nor the use totals.

A region and overriding attributes are all it can hold, and that is the whole of it. The moment you want to count what you are dividing, the answer is not an area but two space lines — make the parent a zone and put spaces with regions beneath it.

Region

A region is written exactly as on a space: the two tokens X?..X? Y?..Y?. A + union, however, cannot be written — one area is one rectangle. If several extents are needed, write several area lines.

Spilling outside the parent's region is the warning SEG02. The test is made against the derived region rather than the declared cells, so a finish placed on the part that a drawn line cut away is caught here.

An area cannot be written on a space with no region (an exterior, say). That one is an error.

grid X 0 3600
grid Y 0 4000
level L1 0 h:2400 slab:150
space /L1/hall hall X1..X2 Y1..Y2
  area X1..X2 Y1-2000..Y2 name:はみ出し
space /out exterior
  area X1..X2 Y1..Y2 name:無理

$ npx tsx src/cli.ts check a2.muro --json
  "code": "SEG02",
  "severity": "warning",
  "message": "The area spills outside the region of /L1/hall",
  "code": "SEG01",
  "severity": "error",
  "message": "An area cannot be written on /out, which has no region",

Attributes

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

Key	Tier	Meaning
name:	interpreted	The subdivision's name. It must be unique within its space
floor:	carry	Floor finish, overriding the parent space's floor: over this extent
spec:	carry	The name of the thing. Carried, never interpreted
<namespace>.<key>:	carry	Anyone may write a dotted key, and core gives its content no meaning at all

Neither use: nor h: nor daylight: can be written. An area is not a room, so it does not carry a room's attributes.

✖ ar.muro:line 5: area (/L1/a) carries use:, which is not in the ledger (check the spelling, or add a namespace if the value is only carried — e.g. acme.use:common)

The name is the identity

When an area carries a name, that name becomes the only way to point at that subdivision inside its space — it is what the set edits of composition look it up by. A duplicated name within one space is therefore the error UID04.

✖ s4.muro:line 6: Duplicate area name within space /L1/a: 同名 (s4.muro:line 5, s4.muro:line 6) — the name is what identifies it inside its container

An area with no name claims no identity and is not in the population of that check.

The indentation rules

• Indentation is one level deep and never nests. Nothing can be indented under an area.
• An area belongs to the space line immediately above it. Any unindented line in between ends that association.
• An area written under a space that expands over a level span is attached to every expanded space.
• It cannot be written on a band member. A member's region is derived, so an extent inside it cannot be written in advance.

✖ b9.muro:line 6: area may not be written on a band member (its region is derived — write a room that needs area by position)

A room that needs an extent inside it is written by position, not by band.

Canonical JSON

An area is emitted under its parent space as areas, keeping the grid-reference spelling as written.

grid X 0 3600
grid Y 0 4000
level L1 0 h:2400 slab:150
space /L1/hall hall X1..X2 Y1..Y2 name:エントランスホール floor:オーク
  area X1..X1+1800 Y1..Y2 name:土間 floor:モルタル

$ npx tsx src/cli.ts json a1.muro
  "spaces": {
    "/L1/hall": {
      "type": "hall",
      "at": [
        "X1",
        "Y1",
        "X2",
        "Y2"
      ],
      "attrs": {
        "floor": "オーク",
        "name": "エントランスホール"
      },
      "areas": [
        {
          "at": [
            "X1",
            "Y1",
            "X1+1800",
            "Y2"
          ],
          "attrs": {
            "floor": "モルタル",
            "name": "土間"
          }
        }
      ]
    }
  },

The counterpart on a boundary

Where a finish changes along a boundary, the counterpart is seg: the stretch where a wall turns to glass, or where the dado is a different material. Where it goes and what governs it is in seg. area holds an extent inside a room; seg holds an interval along a boundary.