Feature extraction based design retrieval

An efficient and flexible indexing mechanism for retrieving design objects that possess similar design features as described by the user is presented. The underlying database is composed of rotational objects represented by constructive solid geometry. Both efficiency and flexibility have been taken into account when building and using indices. Regarding efficiency, the pattern matching machine extracts all features from an input pattern string in a single pass, and the algorithm deriving a pattern string from the PAR (principal axis representation) has a linear time complexity with respect to the number of axis segments in the PAR. As for flexibility, A.V. Aho and M.J. Corasick´s algorithm (1975) automatically constructs the pattern matching machine for any new features and the pattern matching machine extracts multiple features and builds multiple indices automatically. The effort required to build and use engineering indices in a CAD/CAM database management system is illustrated