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The IfcBuildingElementProxy is a proxy definition that provides the same functionality as subtypes of IfcBuildingElement, but without having a predefined meaning of the special type of building element, it represents.

Proxies can also be used as spatial place holders or provisions, that maybe later replaced by special types of elements.

One use of the proxy object is a provision for voids, i.e. where a particular volume of space is requested by some engineering function that might later be accepted or rejected and if accepted potentially transformed into a void within a building element, like a wall opening, or a slab opening. The provision for voids is exchanged as an IfcBuildingElementProxy with the PredefinedType = ProvisionForVoid.

Other usages of IfcBuildingElementProxy include:

HISTORY  New entity in IFC2x.
IFC4 CHANGE  The attribute CompositionType has been replaced by PredefinedType, being a superset of the enumerators.

Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Object Typing

The Object Typing concept applies to this entity as shown in Table 90.

Table 90 — IfcBuildingElementProxy Object Typing

NOTE  The IfcBuildingElementProxyType can be used to share common information among many occurrences of the same proxy without establishing a particular semantic meaning of the type.

If no IfcBuildingElementProxyType is attached (i.e. if only occurrence information is available) the PredefinedType should be provided. If set to .USERDEFINED. a user defined value has to be provided by the ObjectType attribute.

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 91.

Table 91 — IfcBuildingElementProxy Property Sets for Objects

Material Single

The Material Single concept applies to this entity.

The material of the IfcBuildingElementProxy is defined by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

NOTE  It is illegal to assign an IfcMaterial to an IfcBuildingElementProxy with the PredefinedType = ProvisionForVoid.

Material information can also be given at the IfcBuildingElementProxyType, defining the common attribute data for all occurrences of the same type. It is then accessible by the inverse IsTypedBy relationship pointing to IfcBuildingElementProxyType.HasAssociations and via IfcRelAssociatesMaterial.RelatingMaterial to IfcMaterial. If both are given, then the material directly assigned to IfcBuildingElementProxy overrides the material assigned to IfcBuildingElementProxyType.

Spatial Containment

The Spatial Containment concept applies to this entity as shown in Table 92.
IfcBuildingStoreyDefault spatial container
IfcBuildingSpatial container for the element if it cannot be assigned to a building storey
IfcSiteSpatial container for the element in case that it is placed on site (outside of building)

Table 92 — IfcBuildingElementProxy Spatial Containment

The IfcBuildingElementProxy, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

XSD Specification:

 <xs:element name="IfcBuildingElementProxy" type="ifc:IfcBuildingElementProxy" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>
 <xs:complexType name="IfcBuildingElementProxy">
   <xs:extension base="ifc:IfcBuildingElement">
    <xs:attribute name="PredefinedType" type="ifc:IfcBuildingElementProxyTypeEnum" use="optional"/>

EXPRESS Specification:

ENTITY IfcBuildingElementProxy
SUBTYPE OF IfcBuildingElement;
PredefinedType : OPTIONAL IfcBuildingElementProxyTypeEnum;
HasObjectName : EXISTS(SELF\IfcRoot.Name);
CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcBuildingElementProxyTypeEnum.USERDEFINED) OR ((PredefinedType = IfcBuildingElementProxyTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));

Link to EXPRESS-G diagram EXPRESS-G diagram

Formal Propositions:

HasObjectName : A Name attribute should be asserted for a building element proxy.
CorrectPredefinedType : Either the PredefinedType attribute is unset (e.g. because an IfcBuildingElementProxyType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
CorrectTypeAssigned : Either there is no building element proxy type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcBuildingElementProxyType.

Inheritance Graph:

ENTITY IfcBuildingElementProxy
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcObject
ObjectType : OPTIONAL IfcLabel;
IsDeclaredBy : SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares : SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy : SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy : SET OF IfcRelDefinesByProperties FOR RelatedObjects;
ENTITY IfcProduct
ObjectPlacement : OPTIONAL IfcObjectPlacement;
Representation : OPTIONAL IfcProductRepresentation;
ReferencedBy : SET OF IfcRelAssignsToProduct FOR RelatingProduct;
ENTITY IfcElement
Tag : OPTIONAL IfcIdentifier;
FillsVoids : SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement;
ConnectedTo : SET OF IfcRelConnectsElements FOR RelatingElement;
IsInterferedByElements : SET OF IfcRelInterferesElements FOR RelatedElement;
InterferesElements : SET OF IfcRelInterferesElements FOR RelatingElement;
HasProjections : SET OF IfcRelProjectsElement FOR RelatingElement;
ReferencedInStructures : SET OF IfcRelReferencedInSpatialStructure FOR RelatedElements;
HasOpenings : SET OF IfcRelVoidsElement FOR RelatingBuildingElement;
IsConnectionRealization : SET OF IfcRelConnectsWithRealizingElements FOR RealizingElements;
ProvidesBoundaries : SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;
ConnectedFrom : SET OF IfcRelConnectsElements FOR RelatedElement;
ContainedInStructure : SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;
ENTITY IfcBuildingElement
HasCoverings : SET OF IfcRelCoversBldgElements FOR RelatingBuildingElement;
ENTITY IfcBuildingElementProxy
PredefinedType : OPTIONAL IfcBuildingElementProxyTypeEnum;

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