Integrating Implicit Answers with Object-Oriented Queries
Hava T. Siegelmann, B. R. Badrinath · 1991
Queries in object-oriented datab;Lqcs are formulated against a class and retrieve instnnccls of the class sat,is-fying a certain predicate on the att,riblltes of the class. The presence of a class hierarchy, an integral part of any object-oriented data model, allows answers to be expressed implicitly in terms of classes and instances. This enables answers to be provided at different levels of abstraction. Shum and Muntz [SM88] presented a way of providing implicit expressions based on a taxonomy defined over the database. The algorithm presented in [SM88] is optimal in the length of the answer but the clarity of the answer is often poor. In this paper, the fo-cus is on coherent answers: implicit answers that are not necessarily optimal in the number of terms but are easy to comprehend. We show that a uniqlle coherent answer can be obtained efficiently in a top down nlanncr. Since the objective is to provide cohcrcnt, answers, and user queries are formulated by means of query operators to access the database, the standard query operators are redefined to obtain and manipulate coherent answers. Coherent answers are useful in coping with information complexity as they allow answers to be represented ab-stractly and are also a useful rctprescntation tool for complex information systems. 1