Einfügepunkt mit zwei Achsen  zweidimensionaler Raum (2D)  
Axis2 Placement2 D 
The IfcAxis2Placement2D provides location and orientation to place items in a twodimensional space. The attribute RefDirection defines the x axis, the y axis is derived. If the attribute RefDirection is not given, the placement defaults to P[1] (xaxis) as [1.,0.] and P[2] (yaxis) as [0.,1.].
Figure 385 illustrates the definition of the IfcAxis2Placement2D within the twodimensional coordinate system. 

Figure 385 — Axis2 placement 2D 
NOTE Definition according to ISO/CD 1030342:1992
The location and orientation in two dimensional space of two mutually perpendicular axes. An axis2_placement_2d is defined in terms of a point, (inherited from the placement supertype), and an axis. It can be used to locate and originate an object in two dimensional space and to define a placement coordinate system. The entity includes a point which forms the origin of the placement coordinate system. A direction vector is required to complete the definition of the placement coordinate system. The reference direction defines the placement X axis direction, the placement Y axis is derived from this.
NOTE Entity adapted from axis2_placement_2d defined in ISO 1030342.
HISTORY New entity in IFC1.5.
#  Attribute  Type  Cardinality  Description  G 

2  RefDirection  IfcDirection  ?  The direction used to determine the direction of the local X axis. If a value is omited that it defaults to [1.0, 0.0.].  X 
P :=IfcBuild2Axes(RefDirection)  IfcDirection  L[2:2]  P[1]: The normalized direction of the placement X Axis. This is [1.0,0.0] if RefDirection is omitted. P[2]: The normalized direction of the placement Y Axis. This is a derived attribute and is orthogonal to P[1]. If RefDirection is omitted, it defaults to [0.0,1.0] 
X 
#  Attribute  Type  Cardinality  Description  G 

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.
IFC2x3 CHANGE The inverse attribute LayerAssignments has been added. IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.  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.
IFC2x3 CHANGE The inverse attribute StyledByItem has been added.  X  
IfcGeometricRepresentationItem  
IfcPlacement  
1  Location  IfcCartesianPoint  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  The space dimensionality of this class, derived from the dimensionality of the location.  X  
IfcAxis2Placement2D  
2  RefDirection  IfcDirection  ?  The direction used to determine the direction of the local X axis. If a value is omited that it defaults to [1.0, 0.0.].  X 
P :=IfcBuild2Axes(RefDirection)  IfcDirection  L[2:2]  P[1]: The normalized direction of the placement X Axis. This is [1.0,0.0] if RefDirection is omitted. P[2]: The normalized direction of the placement Y Axis. This is a derived attribute and is orthogonal to P[1]. If RefDirection is omitted, it defaults to [0.0,1.0] 
X 
<xs:element name="IfcAxis2Placement2D" type="ifc:IfcAxis2Placement2D" substitutionGroup="ifc:IfcPlacement" nillable="true"/>
<xs:complexType name="IfcAxis2Placement2D">
<xs:complexContent>
<xs:extension base="ifc:IfcPlacement">
<xs:sequence>
<xs:element name="RefDirection" type="ifc:IfcDirection" nillable="true" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
ENTITY IfcAxis2Placement2D
SUBTYPE OF (IfcPlacement);
RefDirection : OPTIONAL IfcDirection;
DERIVE
P : LIST [2:2] OF IfcDirection := IfcBuild2Axes(RefDirection);
WHERE
RefDirIs2D : (NOT (EXISTS (RefDirection))) OR (RefDirection.Dim = 2);
LocationIs2D : SELF\IfcPlacement.Location.Dim = 2;
END_ENTITY;
References: IfcAxis2Placement IfcParameterizedProfileDef