IFC (IFC4X3_ADD1) IfcPresentationLayerAssignment Semantic definition

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.

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

Attribute use definition

Figure 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 overrides the layer assignment of the IfcShapeRepresentation.

instantiation diagram
Figure — Presentation layer assignment Entity inheritance Attributes

# Attribute Type Description
IfcPresentationLayerAssignment (4)
1 Name IfcLabel

Name of the layer.

2 Description OPTIONAL IfcText

Additional description of the layer.

3 AssignedItems SET [1:?] OF IfcLayeredItem

The set of layered items, which are assigned to this layer.

4 Identifier OPTIONAL IfcIdentifier

An (internal) identifier assigned to the layer.

Table Formal propositions

Name Description

The items within the set of AssignedItems that can be assigned to a presentation layer shall be geometric shape representation or representation items.

SIZEOF(QUERY(temp <* AssignedItems | (
  SIZEOF(TYPEOF(temp) * [
)) = SIZEOF(AssignedItems)
Table Formal representation

ENTITY IfcPresentationLayerAssignment
	Name : IfcLabel;
	Description : OPTIONAL IfcText;
	AssignedItems : SET [1:?] OF IfcLayeredItem;
	Identifier : OPTIONAL IfcIdentifier;
	ApplicableItems : SIZEOF(QUERY(temp <* AssignedItems | (
  SIZEOF(TYPEOF(temp) * [
)) = SIZEOF(AssignedItems);
END_ENTITY; References Changelog IFC4

  • where rule, ApplicableItems