bsDD classification mapping and specific pset values

In the videos I have seen about bsDD, including the one in the landing bsDD page, the example used is the one mapping the dutch classification system (NL-SfB) to IFC. It explains that an NL-SfB 22.21 Load Bearing Interior wall is mapped to an IFC object defined as IFCWall, LoadBearing = True and IsExternal = False:

But when I browse the bsDD content for this same element in the NL-SfB 2005 2.2 domain, I get this:

My issue is that the values for IsExternal and for LoadBearing are left unspecified and open. I would have expected that it would categorically say that in order to map an IFCWall to 22.21, LoadBearing needs to True and IsExternal needs to be False. Sure I can deduce the required values from the name of the 22.21 element, but this makes the dictionary, in my opinion, lacking what I understood it would provide: Clarity and an agreed unequivocal mapping. Am I missing something? Actually, I could not find any example in any of the other Domains where it would have some sort of decisive mapping to BuildingSmart pset property values.


Hi @CarlosVasquez, good question. The descriptions next to ‘IsExternal (IFC 4.3)’ and ‘LoadBearing (IFC-4.3)’ are confusing, because they were copied from original IFC properties, but they are not the same. In bSDD there is a ‘property’ and ‘classification property’, which is related to a classification. This means that while ‘property’ allows for both ‘True’ and ‘False’, the ‘Classification Property’ can dictate only ‘True’ etc. That is why when you click on the ‘IsExternal (IFC 4.3)’ classification property, you will get to this page:

instead of this one:

It is not a single relation to an IfcWall, which is internal and load bearing but three separate relations. Please have a look at the attached diagram. Does that answer your question?

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Great! I had not even tried to click on the “IsExternal” property link. Not very obvious, but thanks, this is exactly what I was after.