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	C
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	[1:1]	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	C
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.	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.	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	[1:1]	The space dimensionality of this class, defined by the number of real in the list of DirectionRatios.	X

Formal representations

XSD 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