“…In many applied fields, including tolerancing and metrology (Hillyard and Braid, 1978a;Hillyard and Braid, 1978b;Gossard et al, 1988;Jayaraman and Srinivasan, 1989;Srinivasan and Jayaraman, 1989;Rossignac and Requicha, 1986;Boyer and Stewart, 1991;Boyer and Stewart, 1992;Stewart, 1993), solid modeling (M~intyl~i, 1988, p.110), engineering design (Heisserman and Woodbury, 1992), finite element analysis (Kumar and Gossard, 1992), surface reconstruction (Hoppe et al, 1993), computer graphics (Edelsbrunner and Miicke, 1994), path planning in robotics (Latombe, 1991, p. 91), fairing procedures (Rando and Roulier, 1991), image analysis (Serra, 1982, p. 69), and medical imaging (Peters et al, 1992;Fuchs, 1977), it is natural to require that a perturbed object should have the same topological form as a given original object S.…”