IfcPlacement是放置子类型的抽象超类型，定义项或整个形状表示的位置并提供其方向。所有放置子类型都定义右手笛卡尔坐标系，不允许镜像。
注意笛卡尔变换（包括镜像和缩放）受IfcCartesianTransformationOperator支持
注：定义根据ISO/CD 10303-42:1992
放置相对于其几何上下文的坐标系定位几何项。它定位要定义的项，并在轴放置子类型的情况下给出其方向。
注：实体改编自ISO 10303-42中定义的位置。
IFC1.0中增加的新实体
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcRepresentationItem | |||||
| LayerAssignment | IfcPresentationLayerAssignment @AssignedItems |
S[0:1] | Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items. | X | |
| StyledByItem | IfcStyledItem @Item |
S[0:1] | Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve. | X | |
| IfcGeometricRepresentationItem | |||||
| IfcPlacement | |||||
| 1 | Location | IfcCartesianPoint | [1:1] | The geometric position of a reference point, such as the center of a circle, of the item to be located. | X |
| Dim :=Location.Dim |
IfcDimensionCount | [1:1] | The space dimensionality of this class, derived from the dimensionality of the location. | X | |
EXPRESS Specification
ENTITY IfcPlacement
ABSTRACT SUPERTYPE OF(ONEOF(IfcAxis1Placement, IfcAxis2Placement2D, IfcAxis2Placement3D))
SUBTYPE OF (IfcGeometricRepresentationItem);
Location : IfcCartesianPoint;
DERIVE
Dim : IfcDimensionCount := Location.Dim;
END_ENTITY;