The OODB path-method generator (PMG) using access weights and precomputed access relevance

  • Authors:

  • Ashish Mehta;James Geller;Yehoshua Perl;Erich Neuhold

  • Affiliations:

  • CALC, Polytechnic University, Brooklyn, NY 11201, USA/ E-mail: amehta@calc.poly.edu;CIS Department, NJIT, Newark, NJ 07102, USA/ E-mail: geller@homer.njit.edu, perl@homer.njit.edu;CIS Department, NJIT, Newark, NJ 07102, USA/ E-mail: geller@homer.njit.edu, perl@homer.njit.edu;GMD–/IPSI, Dolivostr. 15, D–/6100 Darmstadt, Germany/ E-mail: neuhold@darmstadt.gmd.de

  • Venue:
  • The VLDB Journal — The International Journal on Very Large Data Bases
  • Year:
  • 1998

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Abstract

A path-method is used as a mechanism in object-oriented databases (OODBs) 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 is a method which traverses from one class through a chain of connections between classes and accesses information at another class. However, it is a difficult task for a casual user or even an application programmer to write path-methods to facilitate queries. This is because it might require comprehensive knowledge of many classes of the conceptual schema that are not directly involved in the query, and therefore may not even be included in a user's (incomplete) view about the contents of the database. We have developed a system, called path-method generator (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 desired one. If the path method is rejected, then the user can utilize his now increased knowledge about the database to request (with additional parameters given) another offer from the PMG. The PMG is based on access weights attached to the connections between classes and precomputed access relevance between every pair of classes of the OODB. Specific rules for access weight assignment and algorithms for computing access relevance appeared in our previous papers [MGPF92, MGPF93, MGPF96]. In this paper, we present a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments identify some of these algorithms as very successful in generating most desired path-methods. The PMG system utilizes these successful algorithms and is thus an efficient tool for aiding the user with the difficult task of querying and updating a large OODB.