digraph G {
  Surface -> {SweptSurface, SurfaceReplica, OrientedSurface, OffsetSurface, ElementarySurface, BoundedSurface};
  SweptSurface -> {SurfaceOfRevolution, SurfaceOfLinearExtrusion};
  ElementarySurface -> {ToroidalSurface, SphericalSurface, Plane, CylindricalSurface, ConicalSurface};
  ToroidalSurface -> {DegenerateToroidalSurface};
  BoundedSurface -> {RectangularTrimmedSurface, RectangularCompositeSurface, CurveBoundedSurface, BSplineSurface};
  BSplineSurface -> {UniformSurface, RationalBSplineSurface, QuasiUniformSurface, BezierSurface, BSplineSurfaceWithKnots};
}