OptiqueVQS: Visual Query Formulation for OBDA

Motivation Ontology Based Data Access (OBDA) [16] is a recently proposed prominent approach that aims at providing domain experts with a direct access to available enterprise data sources without IT-experts being involved. OBDA is an alternative to centralised approaches, where an IT-expert translates the requirements of domain experts into Extract-Transform-Load (ETL) processes to first integrate the data and then to apply predefined analytical reporting tools. Currently, centralised approaches are commonly used in enterprises; they, however, can become too heavy-weight and inflexible in some cases [12], that can be addressed the OBDA approach. The key idea behind OBDA is to use ontologies to mediate between users and data. Ontologies describe the domain of interest on a higher level of abstraction in terms that are clear for domain experts, and introduce modeling concepts such as inheritance and relationships between classes of objects, thus allowing to describe the intended meaning of the ontological vocabulary. Ontologies have become a common and successful mechanism to describe application domains in, e.g., biology, medicine, the (Semantic) Web [13]. This success is partially due to a number of available formal languages for describing ontologies, including RDF(S) [7] and OWL 2 [5] standardised by W3C. In OBDA, users formulate their information needs as queries using terms defined in the ontology, and ontological queries are translated into SQL and executed over the data automatically, without an IT-expert’s intervention. To this end a set of mappings is maintained that describe the relationship between the ontological vocabulary and the elements of the schema of the underlying data. The standard query language for ontologies is SPARQL [8]. Writing queries using SPARQL, however, is not easy for domain experts and thus intuitive visual query formulation support is required for OBDA systems. Existing OBDA systems, e.g., [1, 2, 9, 10, 18–21] typically offer limited or no visual query formulation support. Our goal is to provide a solution for visual query formulation over ontologies that is specifically tailored for OBDA systems. The solution should rely on solid theory, be efficient, support interactive data exploration, and should follow the best Human-Computer Interaction practices to guarantee good usability. In the following we give a short overview of our ideas that were partially implemented in our OptiqueVQS system [22].