#### IfcAxis1Placement

Natural language names

##### Semantic definitions at the entity

Entity definition

Definition from 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 (Z).

> NOTE: Corresponding STEP name: axis1_placement, please refer to ISO/IS 10303-42:1994, p. 28 for the final definition of the formal standard.

> HISTORY: New entity in IFC Release 1.5

Illustration:

| Definition of the IfcAxis1Placement within the three-dimensional coordinate system.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
2 | Axis | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| Z :=NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0])) | IfcDirection | [1:1] | 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.] | X

Formal Propositions

Rule | Description
--- | ---
WR1 | The Axis when given should only reference a three-dimensional IfcDirection.
WR2 | The Cartesian point defining the Location shall have the dimensionality of 3.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRepresentationItem
IfcGeometricRepresentationItem
IfcPlacement
1 | Location | IfcCartesianPoint | [1:1] | The geometric position of a reference point, such as the center of a circle, of the item to be located. | X
| Dim :=Location.Dim | IfcDimensionCount | [1:1] | The space dimensionality of this class, derived from the dimensionality of the location. | X
IfcAxis1Placement
2 | Axis | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| Z :=NVL (IfcNormalise(Axis), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0])) | IfcDirection | [1:1] | 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.] | X

##### Formal representations

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
WR1 : (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
WR2 : SELF\IfcPlacement.Location.Dim = 3;
END_ENTITY;

EXPRESS-G diagram

`

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