5.4.3.61 IfcRelSpaceBoundary2ndLevel

5.4.3.61.1 Semantic definition

The 2nd level space boundary defines the physical or virtual delimiter of a space by the relationship IfcRelSpaceBoundary2ndLevel to the surrounding elements. 2nd level space boundaries are characterized by:

• 2nd level space boundaries still represent building elements that bound the space, but are more granular in that they are subdivided in any of the following cases:
• Differences in materials and/or material assemblies (for example, a wainscot or paneling on the lower portion of a wall).
• Differences in spaces or zones on the other side of the building element (or virtual boundary) represented by the space boundary (for example, two different spaces on the other side of a wall)
• 2nd level space boundaries are differentiated in two ways: virtual or physical and internal or external, whereby any space boundary that is both internal and external has to be split into segments being either internal or external.
• 2nd level space boundaries represent both sides of a heat transfer surface separated by the thickness of the building element. They can be further differentiated in:
• Type 2a that occurs when there is a space on the opposite side of the building element providing the space boundary
• Type 2b occurs if there is a building element on the opposite side of the building element providing the space boundary.
• The connection geometry of 2nd level space boundaries is restricted to planar surfaces only. This means that curved surfaces must be segmented.

2nd level space boundaries define the heat transfer surfaces on both sides of building elements that separate spaces. The generation of 2nd level space boundaries has to take building elements and spaces on the other side into account.

Relationship Use Definitions

As shown in Figure 5.4.3.61.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.

The attribute CorrespondingBoundary with inverse Corresponds is provided to link the pair of space boundaries on the opposite sides of the building element.

Geometry Use Definitions

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

5.4.3.61.2 Entity inheritance

1. • IfcRoot
2. • IfcRelationship
   • IfcObjectDefinition
   • IfcPropertyDefinition
3. • IfcRelConnects
   • IfcRelAssigns
   • IfcRelAssociates
   • IfcRelDeclares
   • IfcRelDecomposes
   • IfcRelDefines
4. • IfcRelSpaceBoundary
   • IfcRelConnectsElements
   • IfcRelConnectsPortToElement
   • IfcRelConnectsPorts
   • IfcRelConnectsStructuralActivity
   • IfcRelConnectsStructuralMember
   • IfcRelContainedInSpatialStructure
   • IfcRelCoversBldgElements
   • IfcRelCoversSpaces
   • IfcRelFillsElement
   • IfcRelFlowControlElements
   • IfcRelInterferesElements
   • IfcRelPositions
   • IfcRelReferencedInSpatialStructure
   • IfcRelSequence
   • IfcRelServicesBuildings
5. • IfcRelSpaceBoundary1stLevel
6. • IfcRelSpaceBoundary2ndLevel

5.4.3.61.3 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.
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.
Click to show 11 hidden inherited attributes Click to hide 11 inherited attributes
IfcRelSpaceBoundary2ndLevel (2)
11	CorrespondingBoundary	OPTIONAL IfcRelSpaceBoundary2ndLevel	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.
	Corresponds	SET [0:1] OF IfcRelSpaceBoundary2ndLevel FOR CorrespondingBoundary	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.

5.4.3.61.4 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.
Click to show 2 hidden inherited concepts Click to hide 2 inherited concepts

5.4.3.61.5 Formal representation

ENTITY IfcRelSpaceBoundary2ndLevel
 SUBTYPE OF (IfcRelSpaceBoundary1stLevel);
	CorrespondingBoundary : OPTIONAL IfcRelSpaceBoundary2ndLevel;
 INVERSE
	Corresponds : SET [0:1] OF IfcRelSpaceBoundary2ndLevel FOR CorrespondingBoundary;
END_ENTITY;