Topology rules that check for 3D issues in feature classes with z-values are needed. For example, '3D gaps' that exist in polygon data because of vertices with differing z-values are not identified with existing 2D topology checks. Additionally, 3D polygon features without any 2D topology problems (e.g. gaps and overlaps) can exist on different planes because of differing z-values. 3D topology checks that identify these types of issues in 3D data would be useful.
