Definition from ISO/CD 10303-42:1992: The vector is defined in terms of the direction and magnitude of the vector. The value of the Magnitude attribute defines the magnitude of the vector.

NOTE The magnitude of the vector can not be reliable calculated from the components of the Orientation attribute. This form of representation was selected to reduce problems with numerical instability. For example a vector of magnitude 2.0 mm and equally inclined to the coordinate axes could be represented with Orientation attribute of (1.0,1.0,1.0).

NOTE Corresponding STEP entity: vector. Please refer to ISO/IS 10303-42:1994, p.27 for the final definition of the formal standard. The derived attribute Dim has been added (see also note at IfcGeometricRepresentationItem).

HISTORY New class in IFC Release 1.0

EXPRESS specification:

ENTITY IfcVector
SUBTYPE OF ( IfcGeometricRepresentationItem);
Orientation  :  IfcDirection;
Magnitude  :  IfcLengthMeasure;
Dim  :  IfcDimensionCount :=  Orientation.Dim;
WR1  :  Magnitude >= 0.0;

Attribute definitions:

Orientation  :  The direction of the vector.
Magnitude  :  The magnitude of the vector. All vectors of Magnitude 0.0 are regarded as equal in value regardless of the orientation attribute.
Dim  :  The space dimensionality of this class, it is derived from Orientation

Formal Propositions:

WR1  :  The magnitude shall be positive or zero.

References (4):

Name Type Referred through Express-G
IfcGeometricRepresentationItem Entity
Diagram 1
IfcLine Entity
Attribute 'Dir'
Diagram 5
IfcSurfaceOfLinearExtrusion Entity
Attribute 'ExtrusionAxis'
Diagram 8
IfcVectorOrDirection Select
Select relation
Diagram 2

Inheritance graph

ENTITY IfcVector;
ENTITY IfcRepresentationItem;
ENTITY IfcGeometricRepresentationItem;
ENTITY IfcVector;
Orientation  :  IfcDirection;
Magnitude  :  IfcLengthMeasure;
Dim  :  IfcDimensionCount :=  Orientation.Dim;