Vorsprung / Auskragung

The projection element is a specialization of the general feature element to represent projections applied to building elements. It represents a solid attached to any element that has physical manifestation.

EXAMPLE  A wall projection such as a pilaster strip is handled by IfcProjectionElement
NOTE  View definitions or implementer agreements may restrict the types of elements to which IfcProjectionElement can be applied.

An IfcProjectionElement has to be linked to a element (all subtypes of IfcElement) by using the IfcRelProjectsElement relationship. Its existence depends on the existence of the master element. The relationship implies a Boolean union operation between the volume of the projection element and the volume of the element.

HISTORY  New entity in IFC2x2.
IFC4 CHANGE  The attribute PredefinedType has been added at the end of attribute list.

Containment Use Definition

The IfcProjectionElement shall not participate in the containment relationship, i.e. it is not linked directly to the spatial structure of the project. It has a mandatory ProjectsElements inverse relationship pointing to the IfcElement that is contained in the spatial structure.

Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 60.

Table 60 — IfcProjectionElement Property Sets for Objects

Quantity Sets

The Quantity Sets concept applies to this entity as shown in Table 61.

Table 61 — IfcProjectionElement Quantity Sets

Product Placement

The Product Placement concept applies to this entity as shown in Table 62.
IfcLocalPlacementIfcLocalPlacementRelative placement according to position and rotation relative to container.
IfcLocalPlacement Absolute placement according to position and rotation of world coordinate system.
IfcGridPlacement Placement according to grid intersection.

Table 62 — IfcProjectionElement Product Placement

The local placement for IfcOpeningRecess is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

Body Geometry

The Body Geometry concept applies to this entity as shown in Table 63.

Table 63 — IfcProjectionElement Body Geometry

The geometric representation of IfcProjectionElement is defined using the swept area solid geometry. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

The following additional constraints apply to the swept solid representation:

As shown in Figure 129, the following interpretation of dimension parameter applies for rectangular projection:

NOTE  Rectangles are now defined centric, the placement location has to be set:
NOTE  The local placement directions for the IfcProjectionElement are only given as an example, other directions are valid as well.

Figure 129 — Projection representation

The general b-rep geometric representation of IfcProjectionElement is defined using the Brep geometry. The Brep representation allows for the representation of complex element shape. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

XSD Specification:

 <xs:element name="IfcProjectionElement" type="ifc:IfcProjectionElement" substitutionGroup="ifc:IfcFeatureElementAddition" nillable="true"/>
 <xs:complexType name="IfcProjectionElement">
   <xs:extension base="ifc:IfcFeatureElementAddition">
    <xs:attribute name="PredefinedType" type="ifc:IfcProjectionElementTypeEnum" use="optional"/>

EXPRESS Specification:

ENTITY IfcProjectionElement
SUBTYPE OF IfcFeatureElementAddition;
PredefinedType : OPTIONAL IfcProjectionElementTypeEnum;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

PredefinedType : Predefined generic type for a projection element that is specified in an enumeration. There may be a property set given specificly for the predefined types.
IFC4 CHANGE The attribute has been added at the end of the entity definition.

Inheritance Graph:

ENTITY IfcProjectionElement
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 IfcFeatureElement
ENTITY IfcFeatureElementAddition
ProjectsElements : IfcRelProjectsElement FOR RelatedFeatureElement;
ENTITY IfcProjectionElement
PredefinedType : OPTIONAL IfcProjectionElementTypeEnum;

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