IFC4 修改属性名称、说明、类别、优先级已添加到属性列表的末尾。层厚度的数据类型放宽为IfcNonNegativeLength Measure。


Formal Propositions

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.





Attribute inheritance

  AssociatedTo IfcRelAssociatesMaterial
S[0:?] Use of the IfcMaterialDefinition subtypes within the material association of an element occurrence or element type. The association is established by the IfcRelAssociatesMaterial relationship. X
  HasExternalReferences IfcExternalReferenceRelationship
S[0:?] Reference to external references, e.g. library, classification, or document information, that are associated to the material. X
  HasProperties IfcMaterialProperties
S[0:?] Material properties assigned to instances of subtypes of IfcMaterialDefinition. X
1 Material IfcMaterial [0:1] 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. X
2 LayerThickness IfcNonNegativeLengthMeasure [1:1] 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.
3 IsVentilated IfcLogical [0:1] 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 IfcLabel [0:1] The name by which the material layer is known. X
5 Description IfcText [0:1] Definition of the material layer in more descriptive terms than given by attributes Name or Category. X
6 Category IfcLabel [0:1] 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:
  • 'Load Bearing' — 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 IfcInteger [0:1] 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
[1:1] Reference to the IfcMaterialLayerSet in which the material layer is included. X

EXPRESS Specification

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





posted @ 2024-02-17 14:40  西北逍遥  阅读(2)  评论(0编辑  收藏  举报