IFC 4.3.x development

8.10.3.7 IfcMaterialLayerSet

Change log

IFC4

additionsattributesDescription

8.10.3.7.1 Semantic definitions at the entity

The IfcMaterialLayerSet is a designation by which materials of an element constructed of a number of material layers is known and through which the relative positioning of individual layers can be expressed.

The Material Layer Set Base (MlsBase) describes the imaginary axis along which the material layers are positioned.

  • In case of assigning the IfcMaterialLayerSet directly to an element or element type, the individual layers are stacked according to their position within the list of MaterialLayers without providing information on how to spatially relate the material layer information to the shape representation of the element or element type.
  • In case of assigning the IfcMaterialLayerSet through an IfcMaterialLayerSetUsage to an element, the MlsBase is positioned along the reference axis or reference plane of the element. An offset from the reference axis or plane to MlsBase is supported by IfcMaterialLayerSetUsage which combines layers and an offset. Offsets from element edges are supported by the subtype IfcMaterialLayerWithOffsets. The positive LayerSetDirection (MlsDirection) describes the direction by which the individual material layers are stacked. The IfcMaterialLayer's are stacked with no gap. Gaps within a material layer set are expressed as layers by themselves.

EXAMPLE A cavity brick wall would be modeled as IfcMaterialLayerSet consisting of three IfcMaterialLayer's: brick, air cavity and brick. The air gap is identified by the IsVentilated flag at IfcMaterialLayer.

HISTORY  New entity in IFC1.0

IFC4 CHANGE  Subtyped from IfcMaterialDefinition, the attribute Description has been added at the end of attribute list.

Attribute use definition

As shown in Figure 1, each IfcMaterialLayerSet implicitly defines a material layer set base line (MlsBase), to which the start of the first IfcMaterialLayer is aligned. The total thickness of a layer set is calculated from the individual layer thicknesses, the first layer starting from the MlsBase and following layers being placed on top of the previous (no gaps or overlaps).

"material layer set"

8.10.3.7.1 Attributes

# Attribute Type Description
IfcMaterialDefinition
AssociatedTo SET [0:?] OF IfcRelAssociatesMaterial FOR RelatingMaterial Use of the IfcMaterialDefinition subtypes within the material association of an element occurrence or element type. The association is established by the IfcRelAssociatesMaterial relationship.

> IFC4 CHANGE  The inverse attribute has been added.
HasExternalReferencesSET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjectsReference to external references, e.g. library, classification, or document information, that are associated to the material.

> IFC4 CHANGE  The inverse attribute has been added.
HasProperties SET [0:?] OF IfcMaterialProperties FOR Material Material properties assigned to instances of subtypes of IfcMaterialDefinition.

> IFC4 CHANGE  The inverse attribute has been added.
IfcMaterialLayerSet
1 MaterialLayers LIST [1:?] OF IfcMaterialLayer Identification of the IfcMaterialLayer’s from which the IfcMaterialLayerSet is composed.
2 LayerSetName OPTIONAL IfcLabel The name by which the IfcMaterialLayerSet is known.
3 Description OPTIONAL IfcText Definition of the IfcMaterialLayerSet in descriptive terms.

> IFC4 CHANGE  The attribute has been added at the end of attribute list.
TotalThickness INVALID Total thickness of the material layer set is derived from the function _IfcMlsTotalThickness._

8.10.3.7.2 Entity inheritance

dot_inheritance IfcMaterialLayerSet IfcMaterialLayerSet IfcMaterialDefinition IfcMaterialDefinition IfcMaterialLayerSet->IfcMaterialDefinition IfcMaterialDefinition_children 6 more... IfcMaterialDefinition_children->IfcMaterialDefinition

8.10.3.7.3 Formal representations

ENTITY IfcMaterialLayerSet
 SUBTYPE OF (IfcMaterialDefinition);
	MaterialLayers : LIST [1:?] OF IfcMaterialLayer;
	LayerSetName : OPTIONAL IfcLabel;
	Description : OPTIONAL IfcText;
 DERIVE
	 TotalThickness : IfcLengthMeasure := IfcMlsTotalThickness(SELF);
END_ENTITY;