#### 8.7.3.1 IfcAxis1Placement

| Position et direction d'un axe
| Einfügepunkt mit einer Achse

The IfcAxis1Placement provides location and direction of a single axis.

| Figure 139 illustrates the definition of the IfcAxis1Placement within the parent three-dimensional coordinate system.
Figure 139 — Axis1 placement

> NOTE Definition according to ISO/CD 10303-42:1992
> The direction and location in three dimensional space of a single axis. An axis1_placement is defined in terms of a locating point (inherited from placement supertype) and an axis direction: this is either the direction of axis or defaults to (0.0,0.0,1.0). The actual direction for the axis placement is given by the derived attribute z.

> NOTE Entity adapted from axis1_placement defined in ISO10303-42.

> HISTORY New entity in IFC1.5

XSD Specification:

<xs:element name="IfcAxis1Placement" type="ifc:IfcAxis1Placement" substitutionGroup="ifc:IfcPlacement" nillable="true"/>
<xs:complexType name="IfcAxis1Placement">
<xs:complexContent>
<xs:extension base="ifc:IfcPlacement"/>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcAxis1Placement

| SUBTYPE OF (IfcPlacement);

Axis | : | OPTIONAL IfcStrippedOptional;

| DERIVE

Z | : | IfcDirection := NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]));

| WHERE

AxisIs3D | : | (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
LocationIs3D | : | SELF\IfcPlacement.Location.Dim = 3;

END_ENTITY;

Attribute Definitions:

Axis | : | The direction of the local Z axis.
Z | : | The normalized direction of the local Z axis. It is either identical with the Axis value, if given, or it defaults to [0.,0.,1.]

Formal Propositions:

AxisIs3D | : | The Axis when given should only reference a three-dimensional IfcDirection.
LocationIs3D | : | The Cartesian point defining the Location shall have the dimensionality of 3.

Inheritance Graph:

ENTITY IfcAxis1Placement

| ENTITY IfcRepresentationItem

| INVERSE

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

| ENTITY IfcGeometricRepresentationItem

| ENTITY IfcPlacement

Location | : | IfcCartesianPoint;

| DERIVE

Dim | : | IfcDimensionCount := Location.Dim;

| ENTITY IfcAxis1Placement

Axis | : | OPTIONAL IfcStrippedOptional;

| DERIVE

Z | : | IfcDirection := NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]));

END_ENTITY;

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