There appears to be an error, or maybe it’s just a typo, in 8.9.3.47. Figure 371 in the entity definition illustrates the use of IfcOffsetCurveByDistances which are defined relative to an IfcAlignmentCurve.
However, in 8.9.3.1 IfcAlignmentCurve is deprecated in IFC 4.3 RC2.
Shouldn’t the illustration in IfcOffsetCurveByDistances be defining curves relative to IfcGradientCurve, IfcCompositeCurve, IfcSegmentedReferenceCurve, or IfcPolyline as described in 5.4.3.1.1?