Definition from buildingSMART: The IfcPropertyDefinition
defines the generalization of all characteristics (i.e. a grouping of
individual properties), that may be assigned to objects. Currently,
subtypes of IfcPropertyDefinition include property
set definitions, and property sets..
Property definitions define information that is shared among
multiple instances of objects. The assignment of the shared information
to objects is handled by the IfcRelDefines
New Entity in IFC Release 2.0
|| Reference to the relationship IfcRelAssociates and thus to those externally defined concepts, like classifications,
documents, or library information, which are associated to the property definition.