IfcObjectPlacement

Semantic definitions at the entity

Entity definition

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,
linear placement: by distance along a curve, with possible offsets.

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.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	PlacementRelTo	IfcObjectPlacement	?	Reference to object placement that provides the relative placement with its placement in a grid, local coordinate system or linear referenced placement. If it is omitted, then in the case of linear placement it is established by the origin of horizontal alignment of the referenced IfcAlignment Axis. In the case of local placement it is established by the geometric representation context.	X
	PlacesObject	IfcProduct @ObjectPlacement	S[0:?]	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.	X
	ReferencedByPlacements	IfcObjectPlacement @PlacementRelTo	S[0:?]	Placements that are given relative to this placement of an object.	X

Attribute

Type

Cardinality

Description

PlacementRelTo

IfcObjectPlacement

Reference to object placement that provides the relative placement with its placement in a grid, local coordinate system or linear referenced placement. If it is omitted, then in the case of linear placement it is established by the origin of horizontal alignment of the referenced IfcAlignment Axis. In the case of local placement it is established by the geometric representation context.

PlacesObject

IfcProduct
@ObjectPlacement

S[0:?]

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

IfcObjectPlacement
@PlacementRelTo

S[0:?]

Placements that are given relative to this placement of an object.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcObjectPlacement
1	PlacementRelTo	IfcObjectPlacement	?	Reference to object placement that provides the relative placement with its placement in a grid, local coordinate system or linear referenced placement. If it is omitted, then in the case of linear placement it is established by the origin of horizontal alignment of the referenced IfcAlignment Axis. In the case of local placement it is established by the geometric representation context.	X
	PlacesObject	IfcProduct @ObjectPlacement	S[0:?]	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.	X
	ReferencedByPlacements	IfcObjectPlacement @PlacementRelTo	S[0:?]	Placements that are given relative to this placement of an object.	X

Formal representations

XML 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:sequence>

     <xs:element name="PlacementRelTo" type="ifc:IfcObjectPlacement" nillable="true" minOccurs="0"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcObjectPlacement

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

  PlacementRelTo : OPTIONAL IfcObjectPlacement;

 INVERSE

  PlacesObject : SET [0:?] OF IfcProduct FOR ObjectPlacement;

  ReferencedByPlacements : SET [0:?] OF IfcObjectPlacement FOR PlacementRelTo;

END_ENTITY;

 EXPRESS-G diagram

	Objektpositionierung
	Object Placement
	Positionnement d'objet