IfcAxis2PlacementLinear

Item	SPF	XML	Change	Description
IFC4x3_RC1 to IFC4x3_RC2
IfcAxis2PlacementLinear			MODIFIED	Name changed from IfcOrientationExpression to IfcAxis2PlacementLinear.
Location	X	X	MODIFIED	Name changed from LateralAxisDirection to Location. Type changed from IfcDirection to IfcPoint. Xsdformat changed from Default to Attribute.
Axis		X	MODIFIED	Name changed from VerticalAxisDirection to Axis. Instantiation changed to OPTIONAL.
RefDirection			ADDED

Semantic definitions at the entity

Entity definition

The IfcAxis2PlacementLinear provides location and orientation to place items in a three-dimensional space confined to the context of a curve. Relative placement axes (Axis and RefDirection) are relative to the curve used for linear referencing provided in IfcPlacement Location (IfcPointByDistanceExpression BasisCurve), maintaining the relationship to the tangent of the curve.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
2	Axis	IfcDirection	?	The exact direction of the local Z Axis.	X
3	RefDirection	IfcDirection	?	The direction used to determine the direction of the local X Axis. In case both Axis and RefDirection are set and not perpendicular an adjustment is necessary to maintain orthogonality to the Axis direction. If RefDirection is omitted, the direction is taken from the curve tangent at Location.	X

Formal Propositions

Rule	Description
WR1
WR2	The Axis and RefDirection shall not be parallel or anti-parallel.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	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	IfcPoint		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
IfcAxis2PlacementLinear
2	Axis	IfcDirection	?	The exact direction of the local Z Axis.	X
3	RefDirection	IfcDirection	?	The direction used to determine the direction of the local X Axis. In case both Axis and RefDirection are set and not perpendicular an adjustment is necessary to maintain orthogonality to the Axis direction. If RefDirection is omitted, the direction is taken from the curve tangent at Location.	X

Formal representations

XML Specification

 <xs:element name="IfcAxis2PlacementLinear" type="ifc:IfcAxis2PlacementLinear" substitutionGroup="ifc:IfcPlacement" nillable="true"/>

 <xs:complexType name="IfcAxis2PlacementLinear">

  <xs:complexContent>

   <xs:extension base="ifc:IfcPlacement">

    <xs:sequence>

     <xs:element name="Axis" type="ifc:IfcDirection" nillable="true" minOccurs="0"/>

     <xs:element name="RefDirection" type="ifc:IfcDirection" nillable="true" minOccurs="0"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcAxis2PlacementLinear

 SUBTYPE OF (IfcPlacement);

  Axis : OPTIONAL IfcDirection;

  RefDirection : OPTIONAL IfcDirection;

 WHERE

  WR1 : 'IFCGEOMETRYRESOURCE.IfcPointByDistanceExpression' IN TYPEOF(SELF\IfcPlacement.Location);
  WR2 : (NOT (EXISTS (Axis))) OR (NOT (EXISTS (RefDirection))) OR (IfcCrossProduct(Axis,RefDirection).Magnitude > 0.0);
END_ENTITY;

 EXPRESS-G diagram