IfcMaterialLayer
实体定义
IfcMaterialLayer是由多个层（一个或多个）构成的元素的单个可识别部分。每个IfcMaterialLayer都具有恒定的厚度，并且沿着MlsBase相对于参考IfcMaterialLayerSet定位。
示例：使用三种IfcMaterialLayer：[1]砖、[2]气隙和[3]砖，对带有砖砌体且中间有气隙的空心墙进行建模。内层“Brick”的名称为“Brick（砖）”，有一个单独的LayerThickness（层厚度），可能还有一个Category（类别）将其指示为“承重”，还有一个Priority（优先级）控制该材质层如何与墙连接中的其他材质层交互。
IfcMaterialLayer的材质层名称可能与引用的IfcMaterial名称不同。
示例绝缘层的IfcMaterialLayer名称可以是“insulation”，而IfcMaterial名称是“聚苯乙烯绝缘板”。
IFC1.5中的新实体
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
| Rule | 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. |
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcMaterialDefinition | |||||
| AssociatedTo | IfcRelAssociatesMaterial @RelatingMaterial |
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 @RelatedResourceObjects |
S[0:?] | Reference to external references, e.g. library, classification, or document information, that are associated to the material. | X | |
| HasProperties | IfcMaterialProperties @Material |
S[0:?] | Material properties assigned to instances of subtypes of IfcMaterialDefinition. | X | |
| IfcMaterialLayer | |||||
| 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. |
X |
| 3 | IsVentilated | IfcLogical | [0:1] | Indication of whether the material layer represents an air layer (or cavity).
|
X |
| 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:
|
X |
| 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. |
X |
| ToMaterialLayerSet | IfcMaterialLayerSet @MaterialLayers |
[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;
INVERSE
ToMaterialLayerSet : IfcMaterialLayerSet FOR MaterialLayers;
WHERE
NormalizedPriority : NOT(EXISTS(Priority)) OR {0 <= Priority <= 100};
END_ENTITY;
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标签：IfcMaterialLayer,material,layer,air,priority,OPTIONAL From： https://www.cnblogs.com/herd/p/17912355.html