Figure 9 A query of an arrangement of arcs in Shape Machine under isometry transformations. the two isometric matches T(x) of the identity rule is given in Figure 9(c). ‘he previous example showed the query of a compound arc whose structural features, including centers of a nd intersections of arcs, could be retrieved from the database of CAD system. The next example in Figur howcases the search of a shape consisting of a rotational arrangement of three arcs such that each arc has ¢ ndpoint registered in the database of a shape to be queried. Clearly, this query can be extended for a variety hapes consisting of three or more arcs or combinations of arcs and straight lines without caring about whet! neir boundaries, endpoints and intersections are registered in the database of the CAD system to be searched. T uery here yields two results because the three-fold dihedral symmetry of the three-lens polygon of order € ivided by the order of symmetry of the rotational symmetry of order 3 as long as both shapes share three symme lements, namely the rotations of order 0°, 120°, and 240° around their centers. The query x of the rotatio: rrangement of the three arcs is shown in Figure 9(a), the trefoil design that is queried in Figure 9(b) and one he two isometric matches 7(x) of the identity rule is given in Figure 9(c). 2.4. Find shapes consisting of arcs under similarity transformations