IFC 4.3.1.0 (IFC4X3_ADD1) development

# 5.4.3.60 IfcRelSpaceBoundary1stLevel

## 5.4.3.60.1 Semantic definition

The 1st level space boundary defines the physical or virtual delimiter of a space by the relationship IfcRelSpaceBoundary1stLevel to the surrounding elements. 1st level space boundaries are characterizeda by:

• 1st level space boundaries are the boundaries of a space defined by the surfaces of building elements bounding this space (physical space boundaries) or by virtual surfaces provided by an adjacent space with no dividing wall.
• 1st level space boundaries do not consider any change of material in the bounding building elements, or different spaces/zones behind a wall or slab (floor or ceiling).
• 1st level space boundaries are differentiated in two ways: virtual or physical and internal,external, or undefined (internal and external) e.g. for a wall that is partially inside and outside.
• 1st level space boundaries form a closed shell around the space (so long as the space is completely enclosed) and include overlapping boundaries representing openings (filled or not) in the building elements (see implementers agreement below).

1st level space boundaries define a space by its boundary surfaces without taking anything on the other side of the bounding elements into account.

Relationship Use Definitions

As shown in Figure 5.4.3.60.A, the attribute ParentBoundary with inverse InnerBoundaries is provided to link the space boundaries of doors, windows, and openings to the parent boundary, such as of a wall or slab.

Geometry Use Definitions

See the definition at the supertype IfcRelSpaceBoundary for guidance on using the connection geometry for first level space boundaries.

## 5.4.3.60.5 Formal representation

ENTITY IfcRelSpaceBoundary1stLevel
SUPERTYPE OF (ONEOF
(IfcRelSpaceBoundary2ndLevel))
SUBTYPE OF (IfcRelSpaceBoundary);
ParentBoundary : OPTIONAL IfcRelSpaceBoundary1stLevel;
INVERSE
InnerBoundaries : SET [0:?] OF IfcRelSpaceBoundary1stLevel FOR ParentBoundary;
END_ENTITY;

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