IfcRelSpaceBoundary2ndLevel

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcRelSpaceBoundary2ndLevel			ADDED

Semantic definitions at the entity

Entity 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 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 176, 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.

Figure 176 — 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.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
11	CorrespondingBoundary	IfcRelSpaceBoundary2ndLevel	?	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.	X
	Corresponds	IfcRelSpaceBoundary2ndLevel @CorrespondingBoundary	S[0:1]	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRoot
1	GlobalId	IfcGloballyUniqueId		Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	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.	X
3	Name	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.	X
4	Description	IfcText	?	Optional description, provided for exchanging informative comments.	X
IfcRelationship
IfcRelConnects
IfcRelSpaceBoundary
5	RelatingSpace	IfcSpaceBoundarySelect		Reference to one spaces that is delimited by this boundary.	X
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.	X
7	ConnectionGeometry	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.	X
8	PhysicalOrVirtualBoundary	IfcPhysicalOrVirtualEnum		Defines, whether the Space Boundary is physical (Physical) or virtual (Virtual).	X
9	InternalOrExternalBoundary	IfcInternalOrExternalEnum		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).	X
IfcRelSpaceBoundary1stLevel
10	ParentBoundary	IfcRelSpaceBoundary1stLevel	?	Reference to the host, or parent, space boundary within which this inner boundary is defined.	X
	InnerBoundaries	IfcRelSpaceBoundary1stLevel @ParentBoundary	S[0:?]	Reference to the inner boundaries of the space boundary. Inner boundaries are defined by the space boundaries of openings, doors and windows.	X
IfcRelSpaceBoundary2ndLevel
11	CorrespondingBoundary	IfcRelSpaceBoundary2ndLevel	?	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.	X
	Corresponds	IfcRelSpaceBoundary2ndLevel @CorrespondingBoundary	S[0:1]	Reference to the other space boundary of the pair of two space boundaries on either side of a space separating thermal boundary element.	X

#	Concept	Template	Model View
IfcRoot
	Identity	Software Identity	General Usage
	Revision Control	Revision Control	General Usage

Formal representations

XML Specification

 <xs:element name="IfcRelSpaceBoundary2ndLevel" type="ifc:IfcRelSpaceBoundary2ndLevel" substitutionGroup="ifc:IfcRelSpaceBoundary1stLevel" nillable="true"/>

 <xs:complexType name="IfcRelSpaceBoundary2ndLevel">

  <xs:complexContent>

   <xs:extension base="ifc:IfcRelSpaceBoundary1stLevel">

    <xs:sequence>

     <xs:element name="CorrespondingBoundary" type="ifc:IfcRelSpaceBoundary2ndLevel" nillable="true" minOccurs="0"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRelSpaceBoundary2ndLevel

 SUBTYPE OF (IfcRelSpaceBoundary1stLevel);

  CorrespondingBoundary : OPTIONAL IfcRelSpaceBoundary2ndLevel;

 INVERSE

  Corresponds : SET [0:1] OF IfcRelSpaceBoundary2ndLevel FOR CorrespondingBoundary;

END_ENTITY;

 EXPRESS-G diagram

	Raumgrenzen 2. Ebene - Relation
	Rel Space Boundary2nd Level
	Limites d'espace de deuxième niveau

IfcRelSpaceBoundary2ndLevel

Semantic definitions at the entity

Inherited definitions from supertypes

Definitions applying to General Usage

Formal representations