8.10.3.6 IfcMaterialLayer

8.10.3.6.1 Semantic definition

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).

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

8.10.3.6.2 Entity inheritance

8.10.3.6.3 Attributes

#	Attribute	Type	Description
IfcMaterialDefinition (3)
	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.
	HasExternalReferences	SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjects	Reference 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.
Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes
IfcMaterialLayer (8)
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' 鈥� for all material layers having a load bearing function. * 'Insulation' 鈥� for all material layers having an insolating function. * 'Inner finish' 鈥� for the material layer being the inner finish. * 'Outer finish' 鈥� 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.

Table 8.10.3.6.A

8.10.3.6.4 Formal propositions

Name	Description
NormalizedPriority	The Property shall all be given as a normalized integer range [0..100], where 0 is the lowest and 100 the highest priority of the material layer.
`NOT(EXISTS(Priority)) OR {0 <= Priority <= 100}`

Table 8.10.3.6.B

8.10.3.6.5 Formal representation

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;