CV-2x3-123 (aka CV-06-123)
Opening elements shall be within the wall face or slab profile (not misused as arbitrary cuttings) [modified 2008-02-26]
Based on IFC2x2, IFC2x3
Initiator ISG Meeting-Munich [modified ISG Meeting-Prague]
Effects Extended Coordination View
Date 2006 02 24 [modified 2008-02-26]
The IfcOpeningElement is used to denote a semantic object being either an opening or a recess. it should not be used in a general sense of a subtraction body (such as in a CSG difference operation). Therefore the IfcOpeningElement should not be used to create arbitrary clippings, cut-out or other features.
The following agreement is made:
*The IfcOpeningElement shall only be used for true openings and recesses created for a particular design intent.
*Geometrically, the IfcOpeningElement is constraint to be within the body of the voided element, with the exception that the extrusion thickness may extend the thickness of the voided element (see also agreement CV-2x3-122).
For all other clippings, cut-outs, etc. the RepresentationType 'Clipping' using (subtype of) IfcHalfSpaceSolid, or 'Brep', or 'CSG' should be used.
Note: see CV-2x3-112 for agreements on support for 'CSG' on export and import.
Figure 1: An example of the illegal use of the IfcOpeningElement for an arbitrary clipping of the body of an IfcWallStandardCase