IfcDirection

Semantic definitions at the entity

Entity definition

The IfcDirection provides a direction in two or three dimensional space depending on the number of DirectionRatio's provided. The IfcDirection does not imply a vector length, and the direction ratios does not have to be normalized.

NOTE Definition according to ISO/CD 10303-42:1992
This entity defines a general direction vector in two or three dimensional space. The actual magnitudes of the components have no effect upon the direction being defined, only the ratios X:Y:Z or X:Y are significant.

NOTE The components of this entity are not normalized. If a unit vector is required it should be normalized before use.

NOTE Entity adapted from direction defined in ISO 10303-42.

HISTORY New entity in IFC1.0

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	DirectionRatios	IfcReal	L[2:3]	The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3])	X
	Dim :=HIINDEX(DirectionRatios)	IfcDimensionCount		The space dimensionality of this class, defined by the number of real in the list of DirectionRatios.	X

Formal Propositions

Rule	Description
MagnitudeGreaterZero	The magnitude of the direction vector shall be greater than zero.

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
IfcDirection
1	DirectionRatios	IfcReal	L[2:3]	The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3])	X
	Dim :=HIINDEX(DirectionRatios)	IfcDimensionCount		The space dimensionality of this class, defined by the number of real in the list of DirectionRatios.	X

Formal representations

XML Specification

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

 <xs:complexType name="IfcDirection">

  <xs:complexContent>

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

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

     <xs:simpleType>

      <xs:restriction>

       <xs:simpleType>

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

       </xs:simpleType>

       <xs:minLength value="2"/>

       <xs:maxLength value="3"/>

      </xs:restriction>

     </xs:simpleType>

    </xs:attribute>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcDirection

 SUBTYPE OF (IfcGeometricRepresentationItem);

  DirectionRatios : LIST [2:3] OF IfcReal;

 DERIVE

  Dim : IfcDimensionCount := HIINDEX(DirectionRatios);

 WHERE

  MagnitudeGreaterZero : SIZEOF(QUERY(Tmp <* DirectionRatios | Tmp <> 0.0)) > 0;
END_ENTITY;

 EXPRESS-G diagram

Item	Change	Description
IFC4 Addendum 1
IfcDirection
DirectionRatios	MODIFIED	Type changed from REAL to IfcReal.

	Richtung
	Direction
	Direction