#### 8.7.3.20 IfcVector

| Vecteur
| Vektor

An IfcVector is a geometric representation item having both a magnitude and direction. The magnitude of the vector is solely defined by the Magnitude attribute and the direction is solely defined by the Orientation attribute.

> NOTE The DirectionRatios of the Orientation attribute are not used to define the magnitude.

> NOTE Definition according to 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. 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 Entity adapted from vector defined in ISO 10303-42.

> HISTORY New entity in IFC1.0

XSD Specification:

<xs:element name="IfcVector" type="ifc:IfcVector" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
<xs:complexType name="IfcVector">
<xs:complexContent>
<xs:extension base="ifc:IfcGeometricRepresentationItem">
<xs:sequence>
<xs:element name="Orientation" type="ifc:IfcDirection" nillable="true"/>
</xs:sequence>
<xs:attribute name="Magnitude" type="ifc:IfcLengthMeasure" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcVector

| SUBTYPE OF (IfcGeometricRepresentationItem);

Orientation | : | IfcDirection;
Magnitude | : | IfcLengthMeasure;

| DERIVE

Dim | : | IfcDimensionCount := Orientation.Dim;

| WHERE

MagGreaterOrEqualZero | : | Magnitude >= 0.0;

END_ENTITY;

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:

MagGreaterOrEqualZero | : | The magnitude shall be positive or zero.

Inheritance Graph:

ENTITY IfcVector

| ENTITY IfcRepresentationItem

| INVERSE

LayerAssignment | : | SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems;
StyledByItem | : | SET [0:1] OF IfcStyledItem FOR Item;

| ENTITY IfcGeometricRepresentationItem

| ENTITY IfcVector

Orientation | : | IfcDirection;
Magnitude | : | IfcLengthMeasure;

| DERIVE

Dim | : | IfcDimensionCount := Orientation.Dim;

END_ENTITY;

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