IfcRelDefinesByProperties

IfcRelDefinesBy is a fundamental relationship entity within the Industry Foundation Classes (IFC) data schema, used to define a relationship between a set of entities and a defining entity. This relationship signifies that the related entities are defined by, or are instances of, the defining entity. Essentially, it establishes ownership or a definitional link.

The IfcRelDefinesBy entity is abstract and serves as a supertype for more specific relationship types. The most common concrete subtypes are IfcRelDefinesByType and IfcRelDefinesByTemplate. IfcRelDefinesByType is used when the defining entity is an IfcTypeObject, which represents a class or type of building element. This establishes that the related elements are instances of that specific type. For example, a set of doors might be related to an IfcDoorType using IfcRelDefinesByType, indicating they all share the characteristics of that door type.

IfcRelDefinesByTemplate is used when the defining entity is an IfcTemplate, which is a reusable definition or parameter set. This relationship indicates that the related entities derive their properties or behavior from the specified template. This is particularly useful for parameterizing objects and ensuring consistency across a project. The IfcRelDefinesBy relationship is crucial for organizing and structuring BIM data, enabling clear classification, instantiation, and templating of building elements and their properties.