voids can be coincident, overlapping, or completely outside
Just be aware that if you use DataCAD to get the area (or perimeter or volume) of a polyline with overlapping or outside voids the result may not be what you expect:
DataCAD will simply subtract the area (or volume) of the void from the area of the main polyline even if the void is not completely within the main polyline (or add the perimeter of the void to the perimeter of the main polyline even some of the edges of the void are coincident or outside of the main polyline).