IfcRelPositions

Item	SPF	XML	Change	Description
IFC4x1 to IFC4x2
IfcRelPositions			ADDED

Semantic definitions at the entity

Entity definition

This connectivity relationship is used to position an element relative to a design grid or alignment curve. As with other connectivity relationships, this implies positioning constraints. Applications should rely on IfcProduct.ObjectPlacement for rendering purposes, and if aware of this positioning relationship, then should ensure that the local placement accurately reflects any positioning relationship.

NOTE The reason for using a relationship for positioning instead of a new subtype of IfcObjectPlacement is to support interoperability with systems that may not support alignment-based positioning. Conceptually, this relationship is no different than any other element connectivity relationship in this regard such as IfcRelConnectsElements.

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
5	RelatingElement	IfcElement	[1:1]	The element to be positioned.	X
6	RelatedPositioningElement	IfcPositioningElement	[1:1]	The positioning element defining one or more axes for relative positioning.	X
7	Axes	IfcInteger	L[1:3]	Indices of the axes defined by the related positioning element. For IfcAlignment, one or two indices may be provided, corresponding to Horizontal and optionally Vertical if positioned relative to the vertical alignment curve; for single alignments, values are always 1.	X
8	RelativePlacement	IfcAxis2Placement3D	[0:1]	Offsets along axes, where for alignment curves, +X refers to the distance along the curve, +Y refers to the distance orthogonal to the curve (positive is to the left if facing in the direction of the alignment, per right-hand coordinate system), +Z refers to a vertical offset where positive is upwards, the Axis and RefDirection is relative to the direction of the alignment.	X
9	DistanceAlong	IfcLengthMeasure	[1:1]	Distance along the alignment curve, where positive is in the direction of the curve. If the distance is less than zero or greater than the extent of the alignment curve, then the alignment curve is assumed to be linear following the orientation at the corresponding boundary.	X
10	OffsetLateral	IfcLengthMeasure	[1:1]	Lateral offset from the alignment curve where positive values indicate to the left and negative values indicate to the right, as facing in the direction of the alignment. If the alignment curve has a superelevation surface defined, then the vertical position is calculated accordingly.	X
11	OffsetVertical	IfcLengthMeasure	[1:1]	Vertical offset where positive values indicate globally upwards and negative values indicate globally downwards.	X
12	PlacementType	IfcAlignmentPlacementEnum	[1:1]	Indicates whether positioning is calculated according to only the horizontal alignment curve, or the vertical alignment curve relative to the horizontal alignment curve.	X
13	TransformType	IfcAlignmentTransformEnum	[1:1]	Indicates whether element is either positioned as a whole, has components and mapped geometry positioned separately, or has geometry warped to follow the alignment curve.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE only the last modification in stored - either as addition, deletion or modification.	X
3	Name	IfcLabel	[0:1]	Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.	X
4	Description	IfcText	[0:1]	Optional description, provided for exchanging informative comments.	X
IfcRelationship
IfcRelConnects
IfcRelPositions
5	RelatingElement	IfcElement	[1:1]	The element to be positioned.	X
6	RelatedPositioningElement	IfcPositioningElement	[1:1]	The positioning element defining one or more axes for relative positioning.	X
7	Axes	IfcInteger	L[1:3]	Indices of the axes defined by the related positioning element. For IfcAlignment, one or two indices may be provided, corresponding to Horizontal and optionally Vertical if positioned relative to the vertical alignment curve; for single alignments, values are always 1.	X
8	RelativePlacement	IfcAxis2Placement3D	[0:1]	Offsets along axes, where for alignment curves, +X refers to the distance along the curve, +Y refers to the distance orthogonal to the curve (positive is to the left if facing in the direction of the alignment, per right-hand coordinate system), +Z refers to a vertical offset where positive is upwards, the Axis and RefDirection is relative to the direction of the alignment.	X
9	DistanceAlong	IfcLengthMeasure	[1:1]	Distance along the alignment curve, where positive is in the direction of the curve. If the distance is less than zero or greater than the extent of the alignment curve, then the alignment curve is assumed to be linear following the orientation at the corresponding boundary.	X
10	OffsetLateral	IfcLengthMeasure	[1:1]	Lateral offset from the alignment curve where positive values indicate to the left and negative values indicate to the right, as facing in the direction of the alignment. If the alignment curve has a superelevation surface defined, then the vertical position is calculated accordingly.	X
11	OffsetVertical	IfcLengthMeasure	[1:1]	Vertical offset where positive values indicate globally upwards and negative values indicate globally downwards.	X
12	PlacementType	IfcAlignmentPlacementEnum	[1:1]	Indicates whether positioning is calculated according to only the horizontal alignment curve, or the vertical alignment curve relative to the horizontal alignment curve.	X
13	TransformType	IfcAlignmentTransformEnum	[1:1]	Indicates whether element is either positioned as a whole, has components and mapped geometry positioned separately, or has geometry warped to follow the alignment curve.	X

Definitions applying to Bridge View

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Bridge View
	User Identity	Bridge View
	Object Ownership	Bridge View

Formal representations

XSD Specification

 <xs:element name="IfcRelPositions" type="ifc:IfcRelPositions" substitutionGroup="ifc:IfcRelConnects" nillable="true"/>

 <xs:complexType name="IfcRelPositions">

  <xs:complexContent>

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

    <xs:sequence>

     <xs:element name="RelatingElement" type="ifc:IfcElement" nillable="true"/>

     <xs:element name="RelatedPositioningElement" type="ifc:IfcPositioningElement" nillable="true"/>

     <xs:element name="RelativePlacement" type="ifc:IfcAxis2Placement3D" nillable="true" minOccurs="0"/>

    </xs:sequence>

    <xs:attribute name="Axes" use="optional">

     <xs:simpleType>

      <xs:restriction>

       <xs:simpleType>

        <xs:list itemType="ifc:IfcInteger"/>

       </xs:simpleType>

       <xs:maxLength value="3"/>

      </xs:restriction>

     </xs:simpleType>

    </xs:attribute>

    <xs:attribute name="DistanceAlong" type="ifc:IfcLengthMeasure" use="optional"/>

    <xs:attribute name="OffsetLateral" type="ifc:IfcLengthMeasure" use="optional"/>

    <xs:attribute name="OffsetVertical" type="ifc:IfcLengthMeasure" use="optional"/>

    <xs:attribute name="PlacementType" type="ifc:IfcAlignmentPlacementEnum" use="optional"/>

    <xs:attribute name="TransformType" type="ifc:IfcAlignmentTransformEnum" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRelPositions

 SUBTYPE OF (IfcRelConnects);

  RelatingElement : IfcElement;

  RelatedPositioningElement : IfcPositioningElement;

  Axes : LIST [1:3] OF IfcInteger;

  RelativePlacement : OPTIONAL IfcAxis2Placement3D;

  DistanceAlong : IfcLengthMeasure;

  OffsetLateral : IfcLengthMeasure;

  OffsetVertical : IfcLengthMeasure;

  PlacementType : IfcAlignmentPlacementEnum;

  TransformType : IfcAlignmentTransformEnum;

END_ENTITY;

 EXPRESS-G diagram

Link to this page