Novel Developments in Ontology-Based Data Access and Integration (NOBDI)
Ontology-Based Data Access and Integration (OBDA/I) is a popular paradigm for overcoming the typical difficulties in accessing and integrating data stored in different kinds of legacy sources, by leveraging a conceptual representation of such data provided in terms of an ontology. To do so, it combines technologies developed in the areas of Knowledge Representation and in the Semantic Web with traditional database systems. The main mechanism for establishing such a combination are RDF-to-database mappings, which allow one to create virtual views characterizing the content of the data sources and to directly relate them to the terms in the ontology. In this tutorial: (i) We provide a general introduction to the principles and basic technologies for OBDA/I, relying on standard languages used in the Semantic Web, such as RDF, the OWL 2 QL ontology language, and the SPARQL query language. (ii) We provide more insights into the theoretical foundations of OBDA/I, by analyzing the approach based on query rewriting and the computational impact of ontologies and mappings on query answering. (iii) We provide an overview on the some recent advancements in OBDA/I concerning non-relational (NoSQL) data sources and the access to cross-linked data sources.