IDS - Allowing two entities, but they have different PrefinedTypes

[fmohus]

I am trying to specity a situation where both IfcSpatialZone and IfcSpace are allowed entities for setting up so called “Functional Unit” zones in the IFC 4 model.

A modeller using IfcSpatialZone shall set Predefined type OCCUPANCY wheras a modeller using IfSpace shall set Predefined type USEREDFINED and ObjectType FUNCTIONALUNIT (or some other name that we specify).

How could allow I for that - but NOT at the same time allowing for the modeller using IfcSpatialZone to set USERDEFINED (and NOT allowing the modeler using IfcSpace to set OCCUPANCY, which does not even exist for IfcSpace)?

I could split the requirements completely, having one for IfcSpatialZone and one for IfcSpace, but the tricky part is that their applicability is “contitional”, i.e. it is REQUIRED to model the fuctional unit zones EITHER at IfcSpatialZone with OCCUPANCY OR with IfcSpace with USERDEFINED and ObjectType FUNCTIONALUNIT - but it is NOT required to do both.

[artur_tomczak]

Hi @fmohus,

From specification point of view, it is recommended to state clearly what is the desired deliverable, while your proposal leaves two alternative options. But you know your needs best - let me try to help you achieve it in IDS.

You could add three specifications:

1. Min=1, (IfcSpatialZone OR IfcSpace) of predefined type (OCCUPANCY OR FUNCTIONALUNIT)
2. Max=0, IfcSpace of predefined type OCCUPANCY
3. Max=0, IfcSpatialZone of predefined type FUNCTIONALUNIT

Note that you don’t need to specify USERDEFINED and attribute, as IDS checker should interpret custom input already as ObjectType value.

Let me know if that works for you.

[fmohus]

Thank you Artur, we will look into it. The reason why this “two option” alternative is relevant is because some CAD-systems haven’t currently implemented support for using IfcSpatialZone (which is the desired entity), I completely agree with you that ideally that should be the only option.