The hierarchy is priority-driven or

The hierarchy is priority-driven organizing of features based on intrinsic property. For solid model, seed wires are used as hint for geometric reasoning, where child feature is seen as grown from a wire on single face of parent feature, sibling features are adjacent through a wire on multiple faces. Forsurfacemodels,compoundsurfacewithmanysinglefaces is first recognized and grouped as flat-type and bend-type by evaluation of average sampled principle curvature. Morphological relationship between the flat and bend group is used to build hierarchy. For example, while flat-in-bend indicates containing relationship, flat-bend-adjacency is sibling relationship. For assembly model, the assembly structure is the TR. Edge property of ADJ captures kinematic pairs between parts, which involves high pair described in CSpace (configuration space) function and six types of low pair (planner,prismatic,revolute,spherical,cylindrical,andscrew).