IfcAlignment2DHorizontal

Item	SPF	XML	Change	Description
IFC4 ADD1 to IFC4x1
IfcAlignment2DHorizontal			ADDED

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	B
1	StartDistAlong	IfcLengthMeasure	[0:1]	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
	ToAlignment	IfcAlignment @Horizontal	S[1:?]	Link to the IfcAlignment for which it defines the horizontal alignment. More then one IfcAlignment can be linked – in this case, the horizontal alignment is shared by several alignments with own vertical alignments.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcAlignment2DHorizontal
1	StartDistAlong	IfcLengthMeasure	[0:1]	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
	ToAlignment	IfcAlignment @Horizontal	S[1:?]	Link to the IfcAlignment for which it defines the horizontal alignment. More then one IfcAlignment can be linked – in this case, the horizontal alignment is shared by several alignments with own vertical alignments.

Formal representations

XSD Specification

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

 <xs:complexType name="IfcAlignment2DHorizontal">

  <xs:complexContent>

   <xs:extension base="ifc:Entity">

    <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;

  StartDistAlong : OPTIONAL IfcLengthMeasure;

  Segments : LIST [1:?] OF IfcAlignment2DHorizontalSegment;

 INVERSE

  ToAlignment : SET [1:?] OF IfcAlignment FOR Horizontal;

END_ENTITY;

 EXPRESS-G diagram