IFC (IFC4X3_ADD2) under development IfcRelSpaceBoundary1stLevel 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 characterized 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, 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.

Figure — Space boundary first level relationships

Geometry Use Definitions

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

# Attribute Type Description
IfcRoot (4)
1 GlobalId IfcGloballyUniqueId

Assignment of a globally unique identifier within the entire software world.

2 OwnerHistory OPTIONAL IfcOwnerHistory

Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object,

3 Name OPTIONAL IfcLabel

Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.

4 Description OPTIONAL IfcText

Optional description, provided for exchanging informative comments.

IfcRelSpaceBoundary (5)
5 RelatingSpace IfcSpaceBoundarySelect

Reference to one space that is delimited by this boundary.

6 RelatedBuildingElement IfcElement

Reference to the Element that defines the Space Boundaries.

7 ConnectionGeometry OPTIONAL IfcConnectionGeometry

Physical representation of the space boundary. Provided as a curve or surface given within the LCS of the space.

8 PhysicalOrVirtualBoundary IfcPhysicalOrVirtualEnum

Defines whether the Space Boundary is PHYISICAL or VIRTUAL.

9 InternalOrExternalBoundary IfcInternalOrExternalEnum

Defines whether the Space Boundary is INTERNAL, or EXTERNAL, i.e. adjacent to open space that can be a partially enclosed space, such as terrace.

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IfcRelSpaceBoundary1stLevel (2)
10 ParentBoundary OPTIONAL IfcRelSpaceBoundary1stLevel

Reference to the host, or parent, space boundary within which this inner boundary is defined.

InnerBoundaries SET [0:?] OF IfcRelSpaceBoundary1stLevel FOR ParentBoundary

Reference to the inner boundaries of the space boundary. Inner boundaries are defined by the space boundaries of openings, doors and windows.

Table Concept usage

Concept Usage Description
IfcRoot (2)
Revision Control General

Ownership, history, and merge state is captured using IfcOwnerHistory.

Software Identity General

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.

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Table Formal representation

ENTITY IfcRelSpaceBoundary1stLevel
 SUBTYPE OF (IfcRelSpaceBoundary);
	ParentBoundary : OPTIONAL IfcRelSpaceBoundary1stLevel;
	InnerBoundaries : SET [0:?] OF IfcRelSpaceBoundary1stLevel FOR ParentBoundary;

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