IfcAlignment2DHorizontal

Semantic definitions at the entity

Entity definition

An IfcAlignment2DHorizontal is a linear reference projected onto the horizontal x/y plane. Points along a horizontal alignment have two coordinate values, x and y in the local Cartesian engineering system.

The horizontal alignment is defined by segments that are connected end-to-start. The transition at the segment connection is not enforced to be tangential, if the “tangential continuity” flag is set to false, otherwise a tangential continuity shall be preserved. Based on the context of the project, they are geo-referenced and convertible into Northing and Easting values.

NOTE Georeferencing is provided by IfcMapConversion through the IfcGeometricRepresentationContext defined at IfcProject.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	StartDistAlong	IfcLengthMeasure	?	The value of the distance along at the start of the horizontal alignment. If omited (standard) it is set to zero.	X
2	Segments	IfcAlignment2DHorizontalSegment	L[1:?]	An ordered list of unique horizontal alignment segments, each (but the last) are joint end to start	X
	ToAlignmentCurve	IfcAlignmentCurve @Horizontal	S[1:?]		X

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
IfcAlignment2DHorizontal
1	StartDistAlong	IfcLengthMeasure	?	The value of the distance along at the start of the horizontal alignment. If omited (standard) it is set to zero.	X
2	Segments	IfcAlignment2DHorizontalSegment	L[1:?]	An ordered list of unique horizontal alignment segments, each (but the last) are joint end to start	X
	ToAlignmentCurve	IfcAlignmentCurve @Horizontal	S[1:?]		X

Formal representations

XML Specification

 <xs:element name="IfcAlignment2DHorizontal" type="ifc:IfcAlignment2DHorizontal" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>

 <xs:complexType name="IfcAlignment2DHorizontal">

  <xs:complexContent>

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

    <xs:sequence>

     <xs:element name="Segments">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcAlignment2DHorizontalSegment" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcAlignment2DHorizontalSegment"/>

       <xs:attribute ref="ifc:cType" fixed="list"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

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

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcAlignment2DHorizontal

 SUBTYPE OF (IfcGeometricRepresentationItem);

  StartDistAlong : OPTIONAL IfcLengthMeasure;

  Segments : LIST [1:?] OF IfcAlignment2DHorizontalSegment;

 INVERSE

  ToAlignmentCurve : SET [1:?] OF IfcAlignmentCurve FOR Horizontal;

END_ENTITY;

 EXPRESS-G diagram

Item	SPF	XML	Change	Description
IFC4x1 Release Candidate 1
IfcAlignment2DHorizontal			ADDED
IFC4x1 Release Candidate 2
IfcAlignment2DHorizontal
ToAlignmentCurve			ADDED
IFC4x1 Release Candidate 3
IfcAlignment2DHorizontal
LayerAssignment			ADDED
StyledByItem			ADDED