oas-core

OAS Core

When to use

Reach for this skill any time you are emitting or modifying the foundational entities of an OAS plan: rooms, walls, openings, curtain walls, roofs, floor slabs, furniture, railings, or annotations. If the task is purely about coordinates and polygons, use oas-geometry instead. If the task is multi-level resolved geometry with stair/elevator connections, use oas-layout.

Key types

• Document metadata + units block (always { length: "mm", angle: "deg" })
• Level — abstract reference plane at an elevation; not a physical element
• Room — bounded space with a boundary_polygon and usage
• Wall — straight line segment with thickness separating spaces; carries adjacent_rooms
• Opening — door or window placed on a wall via position_along_wall_mm
• CurtainWall — glazed envelope; sibling of Wall, not a subtype
• Roof — sloped covering with defines_slope and eave_overhang_mm
• FloorSlab — the physical floor element (distinct from an abstract Level)
• Furniture — placed objects with position + rotation (formerly an extension, now in Core)
• Railing — barrier element; path may include optional z on stair runs
• Annotation — labels, dimensions, notes

Critical rules

1. Integer millimeters everywhere. Every _mm field is an integer; angles use degrees. The only place decimals appear is derived area_m2.
2. type_name on every entity. This is the IFC-style stable classification (e.g. IfcWall, IfcDoor). Vendor-specific families (Revit, etc.) belong in the oas-autodesk extension, never inline here.
3. Adjacency lives on the wall. Encode room neighborhood via the wall's adjacent_rooms array — not on the room.
4. CurtainWall ≠ subtype of Wall. They are siblings (matches IfcCurtainWall vs IfcWall). Don't nest one inside the other.
5. Openings reference walls by id. position_along_wall_mm is measured along that wall's path; validate position + width ≤ wall length before emitting.

Full schema

See docs/core.md for the complete field-by-field reference.

Related skills

• oas-geometry — for the polygon, point, and unit conventions every Core entity inherits
• oas-layout — when Core entities are part of a fully resolved multi-level plan
• oas-extensions — for machinery, materials, Autodesk metadata, MEP, site