Link to this pageThe resource definition data schemas consist of supporting data structures as shown highlighted in blue. Entities and types defined in this layer can be referenced by all entities in the layers below.
Unlike entities in other layers, resource definition data structures cannot exist independently, but can only exist if referenced (directly or indirectly) by one or more entities deriving from IfcRoot. As resource definitions do not have a concept of identity (such as a GUID), multiple objects referencing the same instance of a resource entity does not imply a relationship. For example, two polylines (IfcPolyline) sharing the same instance for a point (IfcCartesianPoint), and two polylines using different instances for identical points (such as both having cordinates 0,0,0) are semantically equivalent. It is recommended (but not required) for applications to minimize file size by sharing identical resource definition instances where possible.
译：资源定义数据模式由支持蓝色突出显示的数据结构组成。在该层中定义的实体和类型可以由下面各层中的所有实体引用。 与其他层中的实体不同，资源定义数据结构不能独立存在，但仅当由来自IfcRoot的一个或多个实体引用（直接或间接）时才存在。由于资源定义不具有身份的概念（例如GUID），引用资源实体的相同实例的多个对象并不意味着关系。例如，两个共线（IFC.PixLink）共享同一个实例的点（IFCARTESTIIAN点），以及使用相同实例的不同实例的两条折线（如两个具有CordANATE 0，0，0）的语义等价。建议（但不要求）应用程序通过尽可能共享相同的资源定义实例来最小化文件大小。（罗柱邦）
NOTE The resource definition layer should not be confused with construction resource entities (IfcResource subtypes). While the terms are similar, they are unrelated concepts.
注意，资源定义层不应该与构建资源实体（ICFRealSub类型）混淆。虽然术语相似，但它们是不相关的概念。
8.1 IfcActorResource(角色资源)
8.2 IfcApprovalResource(审批资源)
8.3 IfcConstraintResource(约束资源)
8.4 IfcCostResource(成本资源)
8.5 IfcDateTimeResource(日期时间资源)
8.6 IfcExternalReferenceResource(外部参考资源)
8.7 IfcGeometricConstraintResource(几何约束资源)
8.8 IfcGeometricModelResource(几何模型资源)
8.9 IfcGeometryResource(几何资源)
8.10 IfcMaterialResource(材质资源)
8.11 IfcMeasureResource(测量资源)
8.12 IfcPresentationAppearanceResource(外观定义资源)
8.13 IfcPresentationDefinitionResource(介绍定义资源)
8.14 IfcPresentationOrganizationResource(介绍组织资源)
8.15 IfcProfileResource(档案资源)
8.16 IfcPropertyResource(属性资源)
8.17 IfcQuantityResource(数量资源)
8.18 IfcRepresentationResource(表示资源)
8.19 IfcStructuralLoadResource(结构荷载资源)
8.20 IfcTopologyResource(拓扑资源)
8.21 IfcUtilityResource(公用资源)