Feature request: ShapeRepresentatation Facet

[civilx64]

It would be helpful to be able to specify that a product must use a specific Entity as its shape representation.

Example 1:

Applicability

All elements with class IFCREINFORCINGBAR (required)

Requirements

ShapeRepresentation must be class IFCSWEPTDISKSOLID

Example 2:

Applicability

All elements with class IFCALIGNMENT

Requirements

Shape Representation must be class IFCCOMPOSITECURVE or IFCGRADIENTCURVE

Perhaps this could be considered for the v1.1 roadmap?

[fissim-at]

This would require the attribute facet to process attributes that reference other entities. Right now, the attribute facet can only process attributes with explicit values.
This topic was already raised here: #424

Hopefully, we can start a discussion about this topic.

[CBenghi]

Shape Representation must be class IFCCOMPOSITECURVE or IFCGRADIENTCURVE

Typing constraints would not fit adequately in the current data structure, this cannot be addressed in 1.0 unless with a terrible hack. I support the idea, but it needs to be addressed more completely in a following version.

Right now, the attribute facet can only process attributes with explicit values.

For 1.0 we can include every direct attribute (e.g. mandating that reference values exist). See my comment in #424.

[aothms]

Question here is also whether to target the RepresentationType (backed by the schema version IfcShapeRepresentationTypes) or the actual entity types of the Items aggregate. Would be good to assess the advantages and disadvantages of each. Probably in terms of this particular example RepresentationType has really limited expressiveness (we only have Curve/2D/3D/Segment) but maybe that's something that should have been differentiated in the schema function as well (wouldn't help us with 4.3 though). Regardless of the approach, when expressing rules here, people should be cognisant of the possibility for nesting of IfcAlignment > IfcAlignment to support reuse of horizontal.

[civilx64]

... this cannot be addressed in 1.0 unless with a terrible hack. I support the idea, but it needs to be addressed more completely in a following version.

Absolutely - I should have clarified that this is a request for v1.1 or later.

[jonatanjacobsson]

Brilliant. This could be quite useful to validate geometry for everyday measurement practices done on-site. Our contractors on-site rely on being able to measure between centerlines for circular IfcDuctSegments or pipesegments amongst others. An facet like this, would help ensure that workflow without going into Gherkin-territory 😅