Shape Similarity Matching Queries

There are two categories of match queries: whole matching and partial matching queries. With whole matching, a query object is compared with a set of objects to find the ones that are either exactly identical or similar to the query object. With partial matching, however, we are interested in finding the objects that have parts that match the query object. In this chapter, we concentrate on whole matching and do not discuss partial matching in detail. We focus on three variations of match queries (EM, RST, and SIM) to cover cases where the database is searched for exactly identical objects; identical objects that are rotation, scaling, and translation invariant (termed I-RST) or identical objects with a specified rotation angle (R), scaling factor (S), translation vector (T), or any combination of the three (S-RST); or similar objects per our definition of similarity. Various studies were conducted in the database area that address shape similarity matching queries. A group of the studies investigate techniques to speed up the similarity between 2-D objects based on shape [28, 29, 31, 41, 42, 53]. They investigated techniques to speed up the search of 2-D “similar” objects to a target object based on their shapes. This is somewhat similar to our SIM query type. For retrieving similar 2D polygon shapes from a CAD database system, previous work is presented in [28, 29, 42].