This class represents a generic and abstract relationship which subtypes are used to:

• Assign a object type to an object occurrence.
• Assign a property set to an object instance.
• Assign a property set template to a property set.

• EXAMPLE: Several instances of windows within the IFC project model may be of the same (catalogue or manufacturer) type. Thereby they share the same properties. This relationship is established by the subtype IfcRelDefinesByType of IfcRelDefines relationship assigning an IfcWindowStyle to multiple IfcWindow occurrences.
• EXAMPLE: The (same) property set, e.g. Pset_ProductManufacturerInfo, keeping the manufacturer name, label and production year of a product, can be assigned to one, or many instances of furnishing. This relationship is established by the subtype IfcRelDefinesByProperties of IfcRelDefines relationship assigning an IfcPropertySet to one or more instances of IfcFurnishingElement.