IfcReference
实体定义
此实体用于引用实例上属性的值。它可以指标量属性的值，也可以指基于集合的属性中的值。引用的属性可以是直接值、对象引用、集合、反向对象引用和反向集合。引用可以被链接以形成对象属性引用的路径。
Attribute definitions
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| 1 | TypeIdentifier | IfcIdentifier | [0:1] | Optional identifier of the entity or type such as 'IfcMaterialLayerSet'. For entity, type, or select-based references within a collection, this resolves the reference to such type. If omitted, the type is assumed to be the same as the declared referencing attribute.
EXAMPLE IfcRelAssociatesMaterial.RelatingMaterial may be resolved to IfcMaterialLayerSet. |
X |
| 2 | AttributeIdentifier | IfcIdentifier | [0:1] | Optionally identifies a direct or inverse attribute within an entity such as 'MaterialLayers'. If TypeIdentifier is specified and refers to an entity, the attribute must exist within the referenced entity. A null value indicates a reference to the type or entity itself, such as for indicating that the type of a value must match a specified constraint. | X |
| 3 | InstanceName | IfcLabel | [0:1] | Optionally identifies an instance within a collection according to name. If the instance has an attribute called 'Name', such attribute is used for comparison; otherwise the first STRING-based attribute of the entity is used.
EXAMPLE IfcRoot-based entities such as IfcPropertySet use the Name attribute; IfcRepresentation entities use the RepresentationIdentifier attribute. |
X |
| 4 | ListPositions | IfcInteger | L[1:?] | Optionally identifies an instance within a collection according to position starting at 1. For referencing single-level collections, this attribute contains a single member; for referencing multi-level collections, then this LIST attribute contains multiple members starting from the outer-most index. | X |
| 5 | InnerReference | IfcReference | [0:1] | Optional reference to an inner value for ENTITY, SELECT, SET, or LIST attributes. A path may be formed by linking IfcReference instances together.
EXAMPLE A material layer thickness may be referenced using several instances: #1=IFCREFERENCE($,'IfcSlab','HasAssociations',#2); #2=IFCREFERENCE($,'IfcMaterialLayerSet','MaterialLayers',#3); #3=IFCREFERENCE('Core','IfcMaterialLayer','LayerThickness',$); |
X |
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcReference | |||||
| 1 | TypeIdentifier | IfcIdentifier | [0:1] | Optional identifier of the entity or type such as 'IfcMaterialLayerSet'. For entity, type, or select-based references within a collection, this resolves the reference to such type. If omitted, the type is assumed to be the same as the declared referencing attribute.
EXAMPLE IfcRelAssociatesMaterial.RelatingMaterial may be resolved to IfcMaterialLayerSet. |
X |
| 2 | AttributeIdentifier | IfcIdentifier | [0:1] | Optionally identifies a direct or inverse attribute within an entity such as 'MaterialLayers'. If TypeIdentifier is specified and refers to an entity, the attribute must exist within the referenced entity. A null value indicates a reference to the type or entity itself, such as for indicating that the type of a value must match a specified constraint. | X |
| 3 | InstanceName | IfcLabel | [0:1] | Optionally identifies an instance within a collection according to name. If the instance has an attribute called 'Name', such attribute is used for comparison; otherwise the first STRING-based attribute of the entity is used.
EXAMPLE IfcRoot-based entities such as IfcPropertySet use the Name attribute; IfcRepresentation entities use the RepresentationIdentifier attribute. |
X |
| 4 | ListPositions | IfcInteger | L[1:?] | Optionally identifies an instance within a collection according to position starting at 1. For referencing single-level collections, this attribute contains a single member; for referencing multi-level collections, then this LIST attribute contains multiple members starting from the outer-most index. | X |
| 5 | InnerReference | IfcReference | [0:1] | Optional reference to an inner value for ENTITY, SELECT, SET, or LIST attributes. A path may be formed by linking IfcReference instances together.
EXAMPLE A material layer thickness may be referenced using several instances: #1=IFCREFERENCE($,'IfcSlab','HasAssociations',#2); #2=IFCREFERENCE($,'IfcMaterialLayerSet','MaterialLayers',#3); #3=IFCREFERENCE('Core','IfcMaterialLayer','LayerThickness',$); |
X |
EXPRESS Specification
ENTITY IfcReference; TypeIdentifier : OPTIONAL IfcIdentifier; AttributeIdentifier : OPTIONAL IfcIdentifier; InstanceName : OPTIONAL IfcLabel; ListPositions : OPTIONAL LIST [1:?] OF IfcInteger; InnerReference : OPTIONAL IfcReference; END_ENTITY;
###########################
标签：IfcReference,attribute,within,entity,such,type From： https://www.cnblogs.com/herd/p/17562648.html