#### 8.5.3.4 IfcObjectPlacement

| Positionnement d'objet
| Objektpositionierung

IfcObjectPlacement is an abstract supertype for the special types defining the object coordinate system. The IfcObjectPlacement has to be provided for each product that has a shape representation.

The object placement can be given:

- absolute: by an axis2 placement, relative to the world coordinate system,
- relative: by an axis2 placement, relative to the object placement of another product,
- by grid reference: by the virtual intersection and reference direction given by two axes of a design grid.

In any case the object placement has to unambiguously define the object coordinate system as either two-dimensional axis placement (IfcAxis2Placement2D) or three-dimensional axis placement (IfcAxis2Placement3D). The axis placement may have to be calculated.

> HISTORY New entity in IFC2x.

XSD Specification:

<xs:element name="IfcObjectPlacement" type="ifc:IfcObjectPlacement" abstract="true" substitutionGroup="ifc:Entity" nillable="true"/>
<xs:complexType name="IfcObjectPlacement" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:Entity"/>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcObjectPlacement

| ABSTRACT SUPERTYPE OF(ONEOF(IfcGridPlacement, IfcLocalPlacement));

| INVERSE

PlacesObject | : | SET [0:?] OF IfcProduct FOR ObjectPlacement;
ReferencedByPlacements | : | SET OF IfcLocalPlacement FOR PlacementRelTo;

END_ENTITY;

Attribute Definitions:

PlacesObject | : | The IfcObjectPlacement shall be used to provide a placement and an object coordinate system for instances of IfcProduct. If an IfcObjectPlacement is shared by many instances of IfcProduct it does not apply a semantic meaning of being a shared placement that needs to be maintained. The same instance of IfcObjectPlacement could simply be used to reduce exchange file size. IFC2x3 CHANGE New inverse attribute. IFC4 CHANGE The cardinality has changed to 0..n to allow reuse of instances of IfcObjectPlacement as placement object in one to many products. It takes also into account that it can act as a placement for IfcStructuralAnalysisModel.
ReferencedByPlacements | : | Placements that are given relative to this placement of an object.

Inheritance Graph:

ENTITY IfcObjectPlacement

| ENTITY IfcObjectPlacement

| INVERSE

PlacesObject | : | SET [0:?] OF IfcProduct FOR ObjectPlacement;
ReferencedByPlacements | : | SET OF IfcLocalPlacement FOR PlacementRelTo;

END_ENTITY;

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