IFC 4.3.x development

5.4.3.58 IfcRelSpaceBoundary2ndLevel

Change log

IFC4

added

5.4.3.58.1 Semantic definitions at the entity

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 or.
  • 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.

NOTE  2nd level space boundaries are used by many analysis packages that require a surface view of the building that can be transformed into the various simple topological models. Examples of such analysis packages include: (1) energy analysis, (2) lighting analysis, (3) fluid dynamics

HISTORY  New entity in IFC4.

Relationship Use Definitions

As shown in Figure 1, 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.

NOTE  The space boundary of the parent is not cut by the inner boundary - both overlap.

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

NOTE  Only 2nd level space boundaries of type A have corresponding boundaries.

"<a href=IfcRelSpaceBoundary2ndLevel"' src="../figures/ifcrelspaceboundary2ndlevel-fig1.png" title="Figure 1 — Space boundary second level relationships"/>

Geometry Use Definitions

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

5.4.3.58.1 Attributes

# Attribute Type Description
IfcRoot
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,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
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.
IfcRelationship
IfcRelConnects
IfcRelSpaceBoundary
5 RelatingSpace IfcSpaceBoundarySelect Reference to one spaces that is delimited by this boundary.
6 RelatedBuildingElement IfcElement Reference to ~~Building~~ Element, that defines the Space Boundaries.

> IFC2x CHANGE  The data type has been changed from IfcBuildingElement to IfcElement with upward compatibility for file based exchange.

> IFC4 CHANGE  The attribute has been changed to be mandatory.
7 ConnectionGeometry OPTIONAL IfcConnectionGeometry Physical representation of the space boundary. Provided as a **curve or** surface given within the LCS of the space.

> IFC2x CHANGE  The data type has been changed from IfcConnectionSurfaceGeometry to IfcConnectionGeometry with upward compatibility for file based exchange.
8 PhysicalOrVirtualBoundary IfcPhysicalOrVirtualEnum Defines, whether the Space Boundary is physical (Physical) or virtual (Virtual).
9 InternalOrExternalBoundaryIfcInternalOrExternalEnum Defines, whether the Space Boundary is internal (Internal), or external, i.e. adjacent to open space (that can be an partially enclosed space, such as terrace (External).
IfcRelSpaceBoundary1stLevel
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.
IfcRelSpaceBoundary2ndLevel
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 CorrespondingBoundaryReference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.

5.4.3.58.2 Entity inheritance

dot_inheritance IfcRelSpaceBoundary2ndLevel IfcRelSpaceBoundary2ndLevel IfcRelSpaceBoundary1stLevel IfcRelSpaceBoundary1stLevel IfcRelSpaceBoundary2ndLevel->IfcRelSpaceBoundary1stLevel IfcRelSpaceBoundary IfcRelSpaceBoundary IfcRelSpaceBoundary1stLevel->IfcRelSpaceBoundary IfcRelConnects IfcRelConnects IfcRelSpaceBoundary->IfcRelConnects IfcRelConnects_children 15 more... IfcRelConnects_children->IfcRelConnects IfcRelationship IfcRelationship IfcRelConnects->IfcRelationship IfcRelationship_children 5 more... IfcRelationship_children->IfcRelationship IfcRoot IfcRoot IfcRelationship->IfcRoot IfcObjectDefinition IfcObjectDefinition IfcObjectDefinition->IfcRoot IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot

5.4.3.58.3 Definitions applying to General Usage

5.4.3.58.3.1 Identity

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

5.4.3.58.3.2 Revision Control

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

5.4.3.58.4 Formal representations

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