Definition from ISO/CD 10303-42:1992: This type identifies the
types of entity which may be selected as the root of a CSG tree including a
single CSG primitive as a special case (currently not in IFC).
Definition from IAI: In the current IFC Release only Boolean
result (IfcBooleanResult) is defined for being a root tree expression
(at IfcCsgSolid). CSG primitives are out of scope for the current IFC
Release.
NOTE Corresponding STEP type:
csg_select, please refer to ISO/IS 10303-42:1994, p.168 for the final
definition of the formal standard.
HISTORY New Type in IFC Release 1.5.1.
