The IFC2x3 occurrence mapping table has a couple of errors that crept in due to some subtle changes between IFC2x3 and IFC4. There are some cases in IFC4 where, when the new occurrence entity was introduced, it wasn't a sub-class of the previously agreed entity in IFC2x3. The table assumed the parent class of the IFC4 instance would be the correct IFC2x3 instance. There are a couple of cases where that was not the case:

1. In IFC2x3 a IfcSpaceHeater instance should be defined by a IfcSpaceHeaterType and should be an occurrence of IfcEnergyConversionDevice - NOT an IfcFlowTerminal.

In IFC4 IfcSpaceHeater was introduced as a sub class of IfcFlowTerminal , not IfcEnergyConversionDevice - hence the error

2. In IFC2x3 a IfcVibrationIsolator instance should be defined by a IfcVibrationIsolatorType and should be an occurrence of IfcEquipmentElement - NOT an IfcElementComponent (which is abstract in IFC2x3).

This occurred for similar reasons to above.

This discrepancy makes a difference because if implementors are checking both the TypeEntity and Occurrence Entity they'll get incorrect results.

Will add a PR to correct this documentation issue.