Some approaches for relational databases flexible querying

摘要

One of the main objectives of third generation databases is to design database management systems which provide users with more and more functionalities. In such a wide context, various proposals have been made in order to introduce some kind of explicit or implicit flexibility into user queries. In this paper, we propose a classification of the various approaches dealing with imprecise queries. Moreover, we show that the approach based on fuzzy sets is powerful enough to answer a wide range of imprecise queries in an appropriate way and to support the expression of the capabilities available in the other classes of solutions. An outline of an SQL-like language allowing for a variety of imprecise queries is also presented.