Materialization of OWL Ontologies from Relational Databases: A Practical Approach

Abstract

Providing both end-users and applications with a uniform way to query legacy databases through a high-level ontology that models both the business logic and the underlying data sources is the main concern in Ontology-based Data Access (OBDA). Our goal in this research is providing tools for performing OBDA with relational and non-relational data sources. Within the OBDA framework, in this work, we present a prototype tool that can access an H2 database, allowing the user to explicitly express mappings, and populating an ontology that can be saved for later querying. We report on the current functionality of our tool, which includes creating, loading, saving a global ontology populated with a database or a CSV file. For the latter, we devised a language for specifying the underlying schema of the CSV file. We argue that this language is better suited than current alternatives such as JSON. Also, the system allows the user to visually express mappings from the database to the ontology and the ability to create databases for testing the behavior of the system in the presence of increasing workloads. Our tests indicate that the system can handle a moderate workload of tables of tens of thousands of records but fails to handle tables of millions of records.