#### 8.12.3.2 IfcPresentationLayerAssignment

| Assignation de calque
| Zuordnung zu Präsentations-Layer

The presentation layer assignment provides the layer name (and optionally a description and an identifier) for a collection of geometric representation items. The IfcPresentationLayerAssignment corresponds to the term "CAD Layer" and is used mainly for grouping and visibility control.

> NOTE The use of presentation layer shall be restricted to simple grouping and displaying purposes.

Visibility and access control and layer style assignment (colour, line style, line width) is handled by the subtype IfcPresentationLayerAssignmentWithStyle.

> NOTE Corresponding ISO 10303 name: presentation layer assignment. Please refer to ISO/IS 10303-46:1994, p. 36 for the final definition of the formal standard.

> HISTORY New entity in IFC2x2.

Attribute use definition

Figure 127 illustrates assignment of items by shape representation or representation item. The set of AssignedItems can either include a whole shape representation, or individual geometric representation items. If both, the IfcShapeRepresentation has a layer assignment, and an individual geometric representation item in the set of IfcShapeRepresentation.Items, then the layer assignment of the IfcGeometricRepresentationItem overides the layer assignment of the IfcShapeRepresentation.

Figure 127 — Presentation layer assignment

XSD Specification:

<xs:element name="IfcPresentationLayerAssignment" type="ifc:IfcPresentationLayerAssignment" substitutionGroup="ifc:Entity" nillable="true"/>
<xs:complexType name="IfcPresentationLayerAssignment">
<xs:complexContent>
<xs:extension base="ifc:Entity">
<xs:sequence>
<xs:element name="AssignedItems">
<xs:complexType>
<xs:group ref="ifc:IfcLayeredItem" maxOccurs="unbounded"/>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcLayeredItem"/>
<xs:attribute ref="ifc:cType" fixed="set"/>
<xs:attribute ref="ifc:arraySize" use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="Name" type="ifc:IfcLabel" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcPresentationLayerAssignment

Name | : | IfcLabel;
Description | : | OPTIONAL IfcStrippedOptional;
AssignedItems | : | SET [1:?] OF IfcLayeredItem;
Identifier | : | OPTIONAL IfcStrippedOptional;

| WHERE

ApplicableItems | : | SIZEOF(QUERY(temp <* AssignedItems | ( SIZEOF(TYPEOF(temp) * [ 'IFCREPRESENTATIONRESOURCE.IFCSHAPEREPRESENTATION', 'IFCGEOMETRYRESOURCE.IFCGEOMETRICREPRESENTATIONITEM', 'IFCGEOMETRYRESOURCE.IFCMAPPEDITEM']) = 1) )) = SIZEOF(AssignedItems);

END_ENTITY;

Attribute Definitions:

Name | : | Name of the layer.
Description | : | Additional description of the layer.
AssignedItems | : | The set of layered items, which are assigned to this layer.
Identifier | : | An (internal) identifier assigned to the layer.

Formal Propositions:

ApplicableItems | : | The items within the set of AssignedItems that can be assigned to a presentation layer shall be geometric shape representation or representation items. IFC4 CHANGE The where rule has been added.

Inheritance Graph:

ENTITY IfcPresentationLayerAssignment

| ENTITY IfcPresentationLayerAssignment

Name | : | IfcLabel;
Description | : | OPTIONAL IfcStrippedOptional;
AssignedItems | : | SET [1:?] OF IfcLayeredItem;
Identifier | : | OPTIONAL IfcStrippedOptional;

END_ENTITY;

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