THE OODB PATH-METHOD GENERATOR (PMG) USING ACCESS WEIGHTS AND PRECOMPUTED ACCESS RELEVANCE

A path-method is used as a mechanism in object-oriented databases (OOD Bs) to retrieve or to update information relevant to one class that is not stored with that class but with some other class. A path-method i s a method which traverses from one class through a chain of connectio ns between classes and accesses information at another class. However, it is a difficult task for a casual user or even an application progr ammer to write path-methods to facilitate queries. This is because it might require comprehensive knowledge of many classes of the conceptua l schema that are not directly involved in the query, and therefore ma y not even be included in a user's (incomplete) view about the content s of the database. We have developed a system, called path-method gene rator (PMG), which generates path-methods automatically according to a user's database-manipulating requests. The PMG offers the user one of the possible path-methods and the user verifies from his knowledge of the intended purpose of the request whether that path-method is the d esired one. If the path method is rejected, then the user can utilize his now increased knowledge about the database to request (with additi onal parameters given) another offer from the PMG. The PMG is based on access weights attached to the connections between classes and precom puted access relevance between every pair of classes of the OODB. Spec ific rules for access weight assignment and algorithms for computing a ccess relevance appeared in our previous papers [MGPF92, MGPF93, MGPF9 6]. In this paper, we present a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments identi fy some of these algorithms as very successful in generating most desi red path-methods. The PMG system utilizes these successful algorithms and is thus an efficient tool for aiding the user with the difficult t ask of querying and updating a large OODB.