8.16 IfcPropertyResource

8.16.1 Schema definition

The IfcPropertyResource defines a basic set of property types that can be associated with occurrence objects (subtypes of IfcObject) and type objects (subtypes of IfcTypeObject) through the IfcPropertySet (defined in the IfcKernel schema). These properties are used to assign property definitions that are semantically defined by a name string and are extensible in terms of their definitions.

The association of attributes to objects can be defined by two different ways:

by defining a type object (IfcTypeObject) which defines a specific object information (including the relevant properties) that is assigned to all instances (or occurrences) of the type object (via the IfcRelDefinesByType relationship).
by defining a property set (IfcPropertySet, a logical grouping of related properties) which defines the common property information for an individual instance (or occurrence), this is done via the IfcRelDefinesByProperties relationship.

The semantic information of what an individual property denotes has to be given by the Name attribute. The Name is human interpretable and can also be computer interpretable by convention. This convention has to be established by implementers' agreements.

All subtypes of IfcProperty are referenced later by the IfcPropertySet. Thereby the IfcPropertySet establishes a tree of property definitions through the IfcSimpleProperty (and its subtypes) and IfcComplexProperty. Any instance of IfcSimpleProperty within this tree shall only be referenced once (by either IfcPropertySet or IfcComplexProperty).