Counted and uncounted divisions

The first 2m of the office, at the entrance, is a hard-floored threshold in mortar. Is that one room or two?

koyu treats this as a design decision and lets you write it either way. But the consequences differ. This page writes both and settles how to choose.

Every output below was actually run.

Two questions decide it

There are only two.

1. Do you want it as a row in the area schedule?
2. Does it matter whether you can walk through it?

If either is yes, it is a counted division — write two spaces. If both are no, it is an uncounted division — write it as an extent inside one space.

How it is written	Area schedule	Circulation graph	What it carries
Two space lines	A row each	An edge	Region, type, every attribute
zone	One row, the sum of its members	None (it has no geometry)	Aggregation and an inherited use:
area (inside a space)	None	None	An extent plus name: floor: spec:
seg (on a boundary)	None	None (it puts no hole in the wall)	A run, and attribute overrides on it

area and seg do not count. They appear in neither area, nor room count, nor the koyu doors graph.

Writing it uncounted

Write the threshold as an extent inside the office. While we are here, write the fact that only part of the exterior wall is a curtain wall, with a seg.

koyu 1.0
name 数えない分節
unit mm

grid X 0 8000
grid Y 0 5000

level L1 0 h:2700 slab:200

space /L1/office office X1..X2 Y1..Y2 name:事務室 floor:タイルカーペット
  area X1..X1+2000 Y1..Y2 name:土間 floor:モルタル
space /out exterior name:外部

boundary /L1/office /out t:180 spec:RC edge:S
  seg w:3000 at:X1+4000 spec:カーテンウォール
  door w:900 h:2100 at:X1+1000 name:D1

✔ Consistent — 2 spaces / 1 boundary

The area schedule is one row.

L1
  /L1/office	事務室	office	40.00 m2
  Subtotal 40.00 m2
Total 40.00 m2 (indoor floor area)
  office: 40.00 m2

The threshold is absent from the graph too. The office is one node, with one door leading out.

/L1/office (事務室)
  — 1 door → /out  (spec:RC)
/out (外部)
  — 1 door → /L1/office  (spec:RC)

However many area lines you stack, the area comes from the parent space's region. Floor finish varies by extent; the totals do not move. If that is what you wanted, you are done.

Writing it counted

The same building, with the threshold and the working floor as separate spaces. The parent is a zone, not a space — a space with a region under another space with a region always overlaps.

koyu 1.0
name 数える分節
unit mm

grid X 0 8000
grid Y 0 5000

level L1 0 h:2700 slab:200

zone /L1/office name:事務室
space /L1/office/doma  hall   X1..X1+2000 Y1..Y2 name:土間 floor:モルタル
space /L1/office/floor office X1+2000..X2 Y1..Y2 name:執務 floor:タイルカーペット
space /out exterior name:外部

boundary /L1/office/doma /L1/office/floor type:open

boundary /L1/office/doma /out t:180 spec:RC edge:S
  door w:900 h:2100 name:D1
boundary /L1/office/floor /out t:180 spec:RC edge:S

✔ Consistent — 3 spaces / 3 boundaries

The area schedule becomes two rows with a zone subtotal.

L1
  /L1/office/doma	土間	hall	10.00 m2
  /L1/office/floor	執務	office	30.00 m2
  Subtotal 40.00 m2
Total 40.00 m2 (indoor floor area)
By zone (counted aggregation):
  /L1/office	事務室	40.00 m2
  hall: 10.00 m2
  office: 30.00 m2

The total is the same 40.00 m2. Changing how it is divided does not move the floor area. What moved is the number of rows, and the grain at which questions can be asked.

1 door — /L1/office/floor → /L1/office/doma → /out

There is now a route from the working floor to the outside. The uncounted version cannot be asked that question at all.

The one line that separates the two

boundary /L1/office/doma /L1/office/floor type:open

The moment a space is split in two, a wall is derived between the halves. The default between touching spaces is a wall, and a wall with no door cannot be walked through. There is no door between the threshold and the working floor, so without type:open the working floor is sealed.

That is what "dividing makes circulation a question" amounts to. Do not divide and it never arises; divide and it must be written.

What area cannot carry

An area is not a room, so it has none of a room's attributes.

The writable keys are name:, floor:, spec:, and namespaced keys containing a dot. use:, h: and daylight: cannot be written.

✖ 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)

Three more limits.

• It cannot hold a boundary. No doors, no windows. Adjacency and passage belong to the parent space.
• One area is one rectangle. + unions cannot be written. For several extents, write several area lines.
• It cannot go on a space with no region. There is no area inside /out.

name: must be unique within the space. The name is identity — it is what a later layer points at when editing.

Why seg does not break the wall

One line separates seg from an opening. An opening breaks the wall; a seg does not.

boundary /L1/office /out t:180 spec:RC edge:S
  seg w:3000 at:X1+4000 spec:カーテンウォール
  door w:900 h:2100 at:X1+1000 name:D1

That seg replaces the spec of a 3000mm run of the south wall and nothing else. No hole opens, no graph edge is added, and the answer from koyu doors does not change. Positioning (w, at, edge) is written exactly as for an opening, and the same checks run in the same order.

seg is for "only part of this one wall is different". If you want to walk through it, that is a door.

Changing your mind

You can. How a thing is divided is written composition, not derivation.

Uncounted → counted. Turn the parent into a zone, rewrite the area as a space, and write the boundary between the two spaces. The area total does not change; the row count and the graph do.

Counted → uncounted. Merge the two space lines into one, and indent one region under it as an area. The zone is no longer needed.

Either way the change shows up in the canonical JSON, and koyu diff names it in the language of composition.

Rules of thumb

Situation	How to write it
Floor finish changes across an extent	area
Recording where furniture or equipment goes	area
Only part of a wall has a different spec or fire rating	seg
You want a row in the area schedule	Two space lines
You want to ask whether it can be walked through	Two space lines
You want the use: totals split	Two space lines
The ceiling height differs	Two space lines (h: is a room attribute)
You want a separate daylight judgement	Two space lines (daylight: is a room attribute)
A grouping with no shape — a dwelling unit, a department, the site	zone

Related

• area — the uncounted division inside a space — the isolation rule and the writable attributes
• seg — the uncounted division on a boundary — positioning and attribute overrides
• space — the counted division
• zone — counted aggregation — a grouping with no shape
• Common traps — the error when the parent is a space