物理量IfcPhysicalQuantity是一个抽象的实体，它包含一个复杂或简单的量的度量，以及一个或多个度量值的用法的语义定义。
Name属性定义度量的实际用法或种类。名称标签的解释必须在实际的交换上下文中建立。此外，信息文本可通过描述属性与每个量相关联。
IFC2x中增加的新实体。它替换了以前IFC版本中使用的calcXxx属性。
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcPhysicalQuantity | |||||
| 1 | Name | IfcLabel | [1:1] | Name of the element quantity or measure. The name attribute has to be made recognizable by further agreements. | X |
| 2 | Description | IfcText | [0:1] | Further explanation that might be given to the quantity. | X |
| HasExternalReferences | IfcExternalReferenceRelationship @RelatedResourceObjects |
S[0:?] | Reference to an external reference, e.g. library, classification, or document information, that is associated to the quantity. | X | |
| PartOfComplex | IfcPhysicalComplexQuantity @HasQuantities |
S[0:1] | Reference to a physical complex quantity in which the physical quantity may be contained. | X | |
EXPRESS Specification
ENTITY IfcPhysicalQuantity
ABSTRACT SUPERTYPE OF(ONEOF(IfcPhysicalComplexQuantity, IfcPhysicalSimpleQuantity));
Name : IfcLabel;
Description : OPTIONAL IfcText;
INVERSE
HasExternalReferences : SET OF IfcExternalReferenceRelationship FOR RelatedResourceObjects;
PartOfComplex : SET [0:1] OF IfcPhysicalComplexQuantity FOR HasQuantities;
END_ENTITY;
原文：https://www.cnblogs.com/herd/p/14397226.html