OJP001 requires ObjectPlacement for aggregated elements without Representation

[fg55b]

Hello everyone,

The rule OJP001 mandates that if an IfcElement is aggregated into another IfcElement, its ObjectPlacement must be provided by an IfcLocalPlacement with PlacementRelTo pointing to the container's placement.

However, this rule is also raised for IfcElement instances that are aggregated but have no Representation. Considering that ObjectPlacement is optional when no representation is defined, is this requirement intended for aggregated elements even without geometry?

[aothms]

Tentatively I would say yes. You see this typically in assemblies, that by themselves do not have a (body) representation, but still have an "insertion point", with its children positioned relative to that. Curious to hear what others think. Not a lot of people are watching this repo though.

[fg55b]

In typical cases where there is geometry, I would totally agree with this logic. However, in this specific scenario where both the whole and the parts lack a body representation, it doesn't seem so straightforward, given the optional character of placement in the schema.

For this specific case, I wonder if verifying the existence of a representation should be done before the 'Then' statements in the rule.

In any case, I understand this is likely an exception that will probably only occur in experimental models, so no worries! It is definitely worth documenting and discussing it though.