Extending the IFC4 Mapping in AC21

[agroni]

Today I was simulating (in my head ) a situation where the owner or investor demands a specific IFC parameter for an element. As an example I will take a Skylight on a flat roof.

In the IFC4 Schema http://www.buildingsmart-tech.org/ifc/IFC4/final/html/ it should be mapped as IfcWindow TypeEnum LIGHTDOME. The Subtype "LIGHTDOME" in AC21 is currently not available to manually predefine or create a new mapping possibility for the skylight. Therefore the skylight can receive a mapping of just IfcWindow.

I just received a response from Graphisoft in this matter, that the option to extend the IFC Schema in Archicad21 is currently not foreseen and it is a future suggestion to be included. Since they did not mention AC22, I suppose it can arrive in AC23 or even later…

Has anyone any idea how to deal with such cases? Thankfully I was not confronted with it, but the only explanation to the investor would be that we are handicapped by our software and he has to accept the IfcWindow.

[stefan]

Similar problem: I am trying to assign "Provision for Void" enumeration value to the PredefinedType of an IfcBuildingElementProxy. This is changed from Ifc2x3, where there was only the CompositionType with other values in the enumeration.

I tried with AC21 and AC22.