Agree how to deal with standard cases about ids

[Moult]

It seems yet again that the decision should be made to support inheritance: #86

Handling these little edge cases are pretty frustrating. Both options are little "gotchas" for implementers.

[aothms]

Well, as discussed, enabling inheritance in evaluation will also result in unexpected (or undesirable) features. Such as the IFC4.3.IfcBuiltElement which has two "functions" (a) the supertype of build(ing) elements (b) the designated entity for use when no applicable element is found (the old proxy elem basically). Without inheritance both of these cases are nice and separated. In my view it's simply a matter of fact that the IFC schemas has too many quirks to expect end-users to make sense/use of inheritance.

Also, with the standard cases being deprecated/partly removed, it warrants some special casing.

These kind of (evaluation-time) expansion rules were also discussed here for type objects without a missing occurence. #116 (comment) I would also here go with option 2.

[pasi-paasiala]

@Moult I'm pretty optimistic that this is the only thing related to inheritance we'd need to implement. Also, if we'd add support for generic inheritance, that might limit the people willing to implement IDS, for example, inside of a CAD tool since they should be aware of the IFC inheritance there and even which schema they should consider even before they've exported their model to any IFC.

[vulevukusej]

Commenting to voice some additional dissatisfaction at the current decision not to implement inheritance. Common requirements that desperately need inheritance to avoid verbose entity definitions in applicability:

• All building elements should be classified
• ... should be assigned to a building storey
• ... should be classified
• ... should have property "StandardCompanyProperty" in "StandardCompanyPset"
• more..

The applicability section ends up being an ugly list of all possible ifc types.

[janbrouwer]

Maybe a special entity facet option: 'all supertypes of ...' for these cases?

[CBenghi]

(a) the supertype of build(ing) elements (b) the designated entity for use when no applicable element is found (the old proxy elem basically). Without inheritance both of these cases are nice and separated

@aothms, would a flag to include/exclude inheritance solve your objection?

[berlotti]

Inheritance is an ongoing/returning debate.
It can be argued both ways.

The use-cases that require this are minimal, while the risk of invalid behaviour in implementations grows exponentially.
The project made the decision in the beginning to not support it and that still seems the correct decision.

We can always reevaluate after 1.0