IFC 4.3.x development

8.10.3.6 IfcMaterialLayer

Change log

IFC4

additions attributes Category
additions attributes Description
additions attributes Name
additions attributes Priority
additions where_rules NormalizedPriority
modificationsattributes LayerThickness definitionChanged from IfcPositiveLengthMeasure to IfcNonNegativeLengthMeasure

8.10.3.6.1 Semantic definitions at the entity

IfcMaterialLayer is a single and identifiable part of an element which is constructed of a number of layers (one or more). Each IfcMaterialLayer has a constant thickness and is located relative to the referencing IfcMaterialLayerSet along the material layer set base (MlsBase).

Air gaps within a material layer set are represented as an IfcMaterialLayer with the attribute IsVentilated having the value TRUE or UNKNOWN. Such air gaps shall be interpreted as voids (not having a material).

EXAMPLE  A cavity wall with brick masonry used with an air gap in between would be modeled using three IfcMaterialLayer's: [1] Brick, [2] Air gap, [3] Brick. The inner layer "Brick" would have a Name = "Brick", an individual LayerThickness, and potentially a Category indicating it as "load bearing", and a Priority that controls how this material layer interacts with other material layers in wall connections.

The IfcMaterialLayer may have a material layer name which may differ from the IfcMaterial name referenced.

EXAMPLE  The IfcMaterialLayer name of an insulation layer can be "Insulation", whereas the IfcMaterial name is "polystyrene insulating boards".

HISTORY  New entity in IFC1.5

IFC4 CHANGE  The attributes Name, Description, Category, Priority have been added at the end of attribute list. Data type of LayerThickness relaxed to IfcNonNegativeLengthMeasure.

8.10.3.6.1 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.
IfcMaterialLayer
1 Material OPTIONAL IfcMaterial Optional reference to the material from which the layer is constructed. Note that if this value is not given, it does not denote a layer with no material (an air gap), it only means that the material is not specified at that point.
2 LayerThickness IfcNonNegativeLengthMeasure The thickness of the material layer. The meaning of "thickness" depends on its usage. In case of building elements elements utilizing IfcMaterialLayerSetUsage, the dimension is measured along the positive LayerSetDirection as specified in IfcMaterialLayerSetUsage.

> NOTE  The attribute value can be 0. for material thicknesses very close to zero, such as for a membrane. Material layers with thickess 0. may not be rendered in the geometric representation.

> IFC4 CHANGE  The attribute datatype has been changed to IfcNonNegativeLengthMeasure allowing for 0. as thickness.
3 IsVentilated OPTIONAL IfcLogical Indication of whether the material layer represents an air layer (or cavity).

* set to TRUE if the material layer is an air gap and provides air exchange from the layer to the outside air.

* set to UNKNOWN if the material layer is an air gap and does not provide air exchange (or when this information about air exchange of the air gap is not available).

* set to FALSE if the material layer is a solid material layer (the default).
4 Name OPTIONAL IfcLabel The name by which the material layer is known.
5 Description OPTIONAL IfcText Definition of the material layer in more descriptive terms than given by attributes Name or Category.
6 Category OPTIONAL IfcLabel Category of the material layer, e.g. the role it has in the layer set it belongs to (such as 'load bearing', 'thermal insulation' etc.). The list of keywords might be extended by model view definitions, however the following keywords shall apply in general:

* 'LoadBearing' — for all material layers having a load bearing function.

* 'Insulation' — for all material layers having an insolating function.

* 'Inner finish' — for the material layer being the inner finish.

* 'Outer finish' — for the material layer being the outer finish.
7 Priority OPTIONAL IfcInteger The relative priority of the layer, expressed as normalised integer range [0..100]. Controls how layers intersect in connections and corners of building elements: a layer from one element protrudes into (i.e. displaces) a layer from another element in a joint of these elements if the former element's layer has higher priority than the latter. The priority value for a material layer in an element has to be set and maintained by software applications in relation to the material layers in connected elements.

> NOTE  The layer priority at a connection may be overridden by the priority attributes of IfcRelConnectsPathElements if that relationship is used to establish a logical connection between two building elements having a layer structure.
ToMaterialLayerSet IfcMaterialLayerSet FOR MaterialLayers Reference to the IfcMaterialLayerSet in which the material layer is included.

8.10.3.6.2 Entity inheritance

dot_inheritance IfcMaterialLayerWithOffsets IfcMaterialLayerWithOffsets IfcMaterialLayer IfcMaterialLayer IfcMaterialLayerWithOffsets->IfcMaterialLayer IfcMaterialDefinition IfcMaterialDefinition IfcMaterialLayer->IfcMaterialDefinition IfcMaterialDefinition_children 6 more... IfcMaterialDefinition_children->IfcMaterialDefinition

8.10.3.6.3 Formal representations

ENTITY IfcMaterialLayer
 SUPERTYPE OF (ONEOF
	(IfcMaterialLayerWithOffsets))
 SUBTYPE OF (IfcMaterialDefinition);
	Material : OPTIONAL IfcMaterial;
	LayerThickness : IfcNonNegativeLengthMeasure;
	IsVentilated : OPTIONAL IfcLogical;
	Name : OPTIONAL IfcLabel;
	Description : OPTIONAL IfcText;
	Category : OPTIONAL IfcLabel;
	Priority : OPTIONAL IfcInteger;
 INVERSE
	ToMaterialLayerSet : IfcMaterialLayerSet FOR MaterialLayers;
 WHERE
	NormalizedPriority : NOT(EXISTS(Priority)) OR {0 <= Priority <= 100};
END_ENTITY;