Specification of the Schema of Spreadsheets for the Materialization of Ontologies from Integrated Data Sources

In Ontology-Based Data Access (OBDA), a knowledge base known as an ontology models both the problem domain and the underlying data sources. We are concerned with providing with tools for performing OBDA with relational and non-relational data sources. We developed an OBDA tool that is able to access H2 databases, CSV files and Excel spreadsheets allowing the user to explicitly formulate mappings, and populating an ontology that can be saved for later querying. In this paper, we present a language for specifying the schema of the data in a spreadsheet data application, which then can be used to access the contents of a set of Excel books with the ultimate goal of materializing its data as an OWL/RDF ontology. We characterize the syntax and semantics of the language, present a prototypical implementation and report on the performance tests showing that our implementation can handle a workload of Excel tables of the order of ten thousand records. We also show a case study in which the ontology of an idealized university library can be defined using the our tool integrating both relational and spreadsheet data.