Ontology based data access with relational databases

As the interconnected devices on the Internet increases around the world, it becomes increasingly important to gather and share meaningful data, also make automatic inferences. As a result, uniform access to stored data, especially in Relational Database Management Systems (RDBMS), is a problem for next-generation web technologies (i.e. Semantic Web) and Internet of Things (IoT). An ontology defines a high-level global schema of data sources and provides an intelligent vocabulary for user queries. Ontology Based Data Access (OBDA) has become an important paradigm for accessing stored data in heterogeneous sources and regarded as a key ingredient of the next-generation of information systems. In this study, stored data in a relational database system were accessed over OBDA model through SPARQL queries according to developed ontology. After developing an ontology that describes the items and relations in the database, mapping process was applied between ontology instances and database entities in a semi-automatic fashion. Equivalent SPARQL queries are automatically generated for the SQL queries sent via the client software and the relational database was accessed. The success of the OBDA procedure was verified by cross-comparison of the data between the relational database and data returned from our model. The response time for each SQL and SPARQL query was also compared. This study may be considered as an authentic solution example to one of the obstacles accessing stored data in relational database system over an ontology for next- generation of internet technologies. All of the tools and the software have been used in this research are also entirely free and based on open source technology.