Efficient Query Answering over Conceptual Schemas of Relational Databases : Technical Report

TL;DR

This paper presents a novel query answering system for relational databases that uses an extended description logic, enabling efficient rewriting and inference over conceptual schemas with an SQL-like interface.

Contribution

It introduces DLR-Lite, an extension of DL-Lite supporting n-ary relations, and a flexible mapping to relational data, enhancing query rewriting and consistency checking.

Findings

Supports polynomial-time query answering with n-ary relations.

Enables inference of implicit information through rewriting.

Provides a formal framework for schema consistency verification.

Abstract

We develop a query answering system, where at the core of the work there is an idea of query answering by rewriting. For this purpose we extend the DL DL-Lite with the ability to support n-ary relations, obtaining the DL DLR-Lite, which is still polynomial in the size of the data. We devise a flexible way of mapping the conceptual level to the relational level, which provides the users an SQL-like query language over the conceptual schema. The rewriting technique adds value to conventional query answering techniques, allowing to formulate simpler queries, with the ability to infer additional information that was not stated explicitly in the user query. The formalization of the conceptual schema and the developed reasoning technique allow checking for consistency between the database and the conceptual schema, thus improving the trustiness of the information system.