Approximate query processing for database flexible querying with aggregates

Abstract

Database flexible querying is an alternative to the classic one for users. The use of Formal Concepts Analysis (FCA) makes it possible to turn approximate answers that those turned over by a classic DataBase Management System (DBMS). Some applications do not need exact answers. However, database flexible querying can be expensive in response time. This time is more significant when the flexible querying require the calculation of aggregate functions ("Sum", "Avg", "Count", "Var" etc.). Online aggregation enables a user to issue an SQL aggregate query, see results immediately, and adjust the processing as the query runs. In this case, the user sees refining estimates of the final aggregation results. In spite of the success which known this method, until now, it hasn't been integrated in flexible querying systems. In this article, we propose an approach which tries to solve this problem by using approximate query processing (AQP). This approach allow user to i) wrote flexible query contains linguistics terms, ii) observe the progress of their aggregation queries and iii) control execution on the fly. We report on an initial implementation of online aggregation in a flexible querying system. © 2012 Springer-Verlag Berlin Heidelberg.