Integrating Relational Databases with the Semantic Web

Printer-friendly version

When: February 25 2015
Where: Winslow Building Room 1140, RPI Campus, Troy, NY, US
Title: Integrating Relational Databases with the Semantic Web
Speaker: Dr. Juan Sequeda

An early vision in Computer Science was to create intelligent systems capable of reasoning on large amounts of data. Independent results in the areas of Description Logic and Relational Databases have advanced us towards this vision. Description Logic research has advanced the understanding of the tradeoff between the computational complexity of reasoning and the expressiveness of logic languages; and now underpins the Semantic Web. Database research has advanced the theory and practice of storage and management of data, embodying features such as views and recursion, which are capable of representing reasoning. Despite the independent advances, the interface between Relational Databases and Semantic Web is poorly understood.

My research revisits this vision with respect to current technology and addresses the following question: How and to what extent can Relational Databases be integrated with the Semantic Web? The thesis is that much of the existing Relational Database infrastructure can be reused to support the Semantic Web.

In this talk, I will provide an answer to the following question: Can a Relational Database be mapped to existing Semantic Web ontologies and act as a reasoner? I will present our system UltrawrapOBDA, an Ontology Based Data Access system comprising bidirectional evaluation, that is, a hybridization of query rewriting (backward chaining) and materialization (forward chaining). UltrawrapOBDA supports inheritance and transitivity.

We observe that by compiling the ontological entailments as mappings, implementing the mappings as SQL views and materializing a subset of the views; the underlying SQL optimizer is able to exploit capabilities beyond relational algebra, such as query rewriting using materialized views and SQL recursion, hence reducing the execution time of a SPARQL query. The ontology expressivity considered is not specific to a single profile, hence I will also speak to a new proposal: OWL-SQL.

I will close with a discussion on the extent that Relational Databases can integrated with the Semantic Web and open problems.

Juan F. Sequeda defended his PhD in Computer Science from the University of Texas at Austin in Fall 2014 and is a 2010-2013 NSF Graduate Research Fellow. His research interests are on the intersection between Relational Databases and Semantic Web and received the Best Student Paper at ISWC 2014, nominated to Best Student Paper at ISWC 2013 and 2nd Place in the 2013 Semantic Web Challenge. He is the developer of Ultrawrap a system that virtualizes Relational Databases as Semantic Web data sources, which has spun-off into a startup, Capsenta. Juan was an invited member to the W3C Relational Database to RDF Working Group and is the editor of the Direct Mapping standard. Juan is an Editorial Board member of the Journal of Web Semantics and a Senior PC member of ISWC 2015. He is also the co-creator of the Consuming Linked Data Workshop series co-located at ISWC.