Returns the value of IsDecomposedBy attribute. This attribute represents references to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).

IFC4 CHANGE: The inverse attribute data type has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.